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Liu SJ, Lee SY, Pivetti C, Kulubya E, Wang A, Farmer DL, Ghiasi S, Yang W. Recovering fetal signals transabdominally through interferometric near-infrared spectroscopy (iNIRS). BIOMEDICAL OPTICS EXPRESS 2023; 14:6031-6047. [PMID: 38021126 PMCID: PMC10659808 DOI: 10.1364/boe.500898] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/18/2023] [Revised: 09/30/2023] [Accepted: 10/13/2023] [Indexed: 12/01/2023]
Abstract
Noninvasive transabdominal fetal pulse oximetry can provide clinicians critical assessment of fetal health and potentially contribute to improved management of childbirth. Conventional pulse oximetry through continuous wave (CW) light has challenges measuring the signals from deep tissue and separating the weak fetal signal from the strong maternal signal. Here, we propose a new approach for transabdominal fetal pulse oximetry through interferometric near-infrared spectroscopy (iNIRS). This approach provides pathlengths of photons traversing the tissue, which facilitates the extraction of fetal signals by rejecting the very strong maternal signal from superficial layers. We use a multimode fiber combined with a mode-field converter at the detection arm to boost the signal of iNIRS. Together, we can detect signals from deep tissue (>∼1.6 cm in sheep abdomen and in human forearm) at merely 1.1 cm distance from the source. Using a pregnant sheep model, we experimentally measured and extracted the fetal heartbeat signals originating from deep tissue. This validated a key step towards transabdominal fetal pulse oximetry through iNIRS and set a foundation for further development of this method to measure the fetal oxygen saturation.
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Affiliation(s)
- Shing-Jiuan Liu
- Department of Electrical and Computer Engineering, University of California, Davis, Davis, CA 95616, USA
| | - Su Yeon Lee
- Department of Surgery, University of California, Davis, Sacramento, CA 95817, USA
| | - Christopher Pivetti
- Department of Surgery, University of California, Davis, Sacramento, CA 95817, USA
| | - Edwin Kulubya
- Department of Surgery, University of California, Davis, Sacramento, CA 95817, USA
| | - Aijun Wang
- Department of Surgery, University of California, Davis, Sacramento, CA 95817, USA
- Department of Biomedical Engineering, University of California, Davis, Davis, CA 95616, USA
| | - Diana L. Farmer
- Department of Surgery, University of California, Davis, Sacramento, CA 95817, USA
| | - Soheil Ghiasi
- Department of Electrical and Computer Engineering, University of California, Davis, Davis, CA 95616, USA
| | - Weijian Yang
- Department of Electrical and Computer Engineering, University of California, Davis, Davis, CA 95616, USA
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Wu J, McKnight JC, Bønnelycke EMS, Bosco G, Giacon TA, Kainerstorfer JM. Self-calibrated pulse oximetry algorithm based on photon pathlength change and the application in human freedivers. JOURNAL OF BIOMEDICAL OPTICS 2023; 28:115002. [PMID: 38078151 PMCID: PMC10704087 DOI: 10.1117/1.jbo.28.11.115002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/06/2023] [Revised: 10/27/2023] [Accepted: 10/30/2023] [Indexed: 12/18/2023]
Abstract
Significance Pulse oximetry estimates the arterial oxygen saturation of hemoglobin (SaO 2 ) based on relative changes in light intensity at the cardiac frequency. Commercial pulse oximeters require empirical calibration on healthy volunteers, resulting in limited accuracy at low oxygen levels. An accurate, self-calibrated method for estimating SaO 2 is needed to improve patient monitoring and diagnosis. Aim Given the challenges of calibration at low SaO 2 levels, we pursued the creation of a self-calibrated algorithm that can effectively estimate SaO 2 across its full range. Our primary objective was to design and validate our calibration-free method using data collected from human subjects. Approach We developed an algorithm based on diffuse optical spectroscopy measurements of cardiac pulses and the modified Beer-Lambert law (mBLL). Recognizing that the photon mean pathlength (⟨ L ⟩ ) varies with SaO 2 related absorption changes, our algorithm aligns/fits the normalized ⟨ L ⟩ (across wavelengths) obtained from optical measurements with its analytical representation. We tested the algorithm with human freedivers performing breath-hold dives. A continuous-wave near-infrared spectroscopy probe was attached to their foreheads, and an arterial cannula was inserted in the radial artery to collect arterial blood samples at different stages of the dive. These samples provided ground-truth SaO 2 via a blood gas analyzer, enabling us to evaluate the accuracy of SaO 2 estimation derived from the NIRS measurement using our self-calibrated algorithm. Results The self-calibrated algorithm significantly outperformed the conventional method (mBLL with a constant ⟨ L ⟩ ratio) for SaO 2 estimation through the diving period. Analyzing 23 ground-truth SaO 2 data points ranging from 41% to 100%, the average absolute difference between the estimated SaO 2 and the ground truth SaO 2 is 4.23 % ± 5.16 % for our algorithm, significantly lower than the 11.25 % ± 13.74 % observed with the conventional approach. Conclusions By factoring in the variations in the spectral shape of ⟨ L ⟩ relative to SaO 2 , our self-calibrated algorithm enables accurate SaO 2 estimation, even in subjects with low SaO 2 levels.
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Affiliation(s)
- Jingyi Wu
- Carnegie Mellon University, Department of Biomedical Engineering, Pittsburgh, Pennsylvania, United States
| | - J. Chris McKnight
- University of St Andrews, Sea Mammal Research Unit, St Andrews, United Kingdom
| | | | - Gerardo Bosco
- University of Padua, Department of Biomedical Sciences, Padua, Italy
| | - Tommaso Antonio Giacon
- University of Padua, Department of Biomedical Sciences, Padua, Italy
- Padua University Hospital, Institute of Anesthesia and Intensive Care, Padua, Italy
- University of Padua, Department of Medicine, Padua, Italy
| | - Jana M. Kainerstorfer
- Carnegie Mellon University, Department of Biomedical Engineering, Pittsburgh, Pennsylvania, United States
- Carnegie Mellon University, Neuroscience Institute, Pittsburgh, Pennsylvania, United States
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Vali K, Vafi A, Kasap B, Ghiasi S. BASS: Safe Deep Tissue Optical Sensing for Wearable Embedded Systems. ACM TRANSACTIONS ON EMBEDDED COMPUTING SYSTEMS : TECS 2023; 22:122. [PMID: 38264154 PMCID: PMC10805365 DOI: 10.1145/3607916] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/23/2023] [Accepted: 07/13/2023] [Indexed: 01/25/2024]
Abstract
In wearable optical sensing applications whose target tissue is not superficial, such as deep tissue oximetry, the task of embedded system design has to strike a balance between two competing factors. On one hand, the sensing task is assisted by increasing the radiated energy into the body, which in turn, improves the signal-to-noise ratio (SNR) of the deep tissue at the sensor. On the other hand, patient safety consideration imposes a constraint on the amount of radiated energy into the body. In this paper, we study the trade-offs between the two factors by exploring the design space of the light source activation pulse. Furthermore, we propose BASS, an algorithm that leverages the activation pulse design space exploration, which further optimizes deep tissue SNR via spectral averaging, while ensuring the radiated energy into the body meets a safe upper bound. The effectiveness of the proposed technique is demonstrated via analytical derivations, simulations, and in vivo measurements in both pregnant sheep models and human subjects.
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Affiliation(s)
- Kourosh Vali
- University of California, Davis, Electrical and Computer Engineering Department, USA
| | - Ata Vafi
- University of California, Davis, Electrical and Computer Engineering Department, USA
| | - Begum Kasap
- University of California, Davis, Electrical and Computer Engineering Department, USA
| | - Soheil Ghiasi
- University of California, Davis, Electrical and Computer Engineering Department, USA
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Kasap B, Vali K, Qian W, Saffarpour M, Fowler R, Ghiasi S. Robust Fetal Heart Rate Tracking through Fetal Electrocardiography (ECG) and Photoplethysmography (PPG) Fusion . ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2023; 2023:1-4. [PMID: 38083436 DOI: 10.1109/embc40787.2023.10341068] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/18/2023]
Abstract
Fetal electrocardiogram (fECG) or photoplethysmogram (fPPG) devices are being developed for fetal heart rate (FHR) monitoring. However, deep tissue sensing is challenged by low fetal signal-to-noise ratio (SNR). Data quality is easily degraded by motion, or interference from maternal tissues and data losses can happen due to communication faults. In this paper, we propose to combine fECG and fPPG measurements in order to increase robustness against such dynamic challenges and increase FHR estimation accuracy. To the author's knowledge the fusion of two sensory data types (fECG, fPPG) has not been investigated for FHR tracking purposes in the literature. The proposed methods are evaluated on real-world data captured from gold-standard large pregnant animal experiments. A particle filtering algorithm with sensor fusion in the measurement likelihood, called KUBAI, is used to estimate FHR. Fusion of PPG&ECG data resulted in 36.6% improvement in root-mean-square-error (RMSE) and 20.3% improvement in R2 correlation between estimated and reference FHR values compared to single sensor-type (PPG-only or ECG-only) data. We demonstrate that using different types of sensory data improves the robustness and accuracy of FHR tracking.
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Joarder R, Kasap B, Ghiasi S. RT-TRAQ: An algorithm for real-time tracking of faint quasi-periodic signals in noisy time series. SMART HEALTH (AMSTERDAM, NETHERLANDS) 2023; 28:100392. [PMID: 37974565 PMCID: PMC10653118 DOI: 10.1016/j.smhl.2023.100392] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2023]
Abstract
We present an algorithm for live tracking of quasi-periodic faint signals in non-stationary, noisy, and phase-desynchronized time series measurements that commonly arise in embedded applications, such as wearable health monitoring. The first step of Rt-Traq is to continuously select fixed-length windows based on the rise or fall of data values in the stream. Subsequently, Rt-Traq calculates an averaged representative window, and its spectrum, whose frequency peaks reveal the underlying quasi-periodic signals. As each new data sample comes in, Rt-Traq incrementally updates the spectrum, to continuously track the signals through time. We develop several alternate implementations of the proposed algorithm. We evaluate their performance in tracking maternal and fetal heart rate using non-invasive photoplethysmography (PPG) data collected by a wearable device from animal experiments as well as a number of pregnant women who participated in our study. Our empirical results demonstrate improvements compared to competing approaches. We also analyze the memory requirement and complexity trade-offs between the implementations, which impact their demand on platform resources for real-time operation.
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Affiliation(s)
- Rishad Joarder
- Dept. of Electrical and Computer Engineering, University of California Davis, Davis, CA 95616, USA
| | - Begum Kasap
- Dept. of Electrical and Computer Engineering, University of California Davis, Davis, CA 95616, USA
| | - Soheil Ghiasi
- Dept. of Electrical and Computer Engineering, University of California Davis, Davis, CA 95616, USA
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6
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Elron E, Bromiker R, Gleisner O, Yosef-Hai O, Goldberg O, Nitzan I, Nitzan M. Overestimation of Oxygen Saturation Measured by Pulse Oximetry in Hypoxemia. Part 1: Effect of Optical Pathlengths-Ratio Increase. SENSORS (BASEL, SWITZERLAND) 2023; 23:1434. [PMID: 36772474 PMCID: PMC9921559 DOI: 10.3390/s23031434] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/24/2022] [Revised: 01/06/2023] [Accepted: 01/20/2023] [Indexed: 06/18/2023]
Abstract
On average, arterial oxygen saturation measured by pulse oximetry (SpO2) is higher in hypoxemia than the true oxygen saturation measured invasively (SaO2), thereby increasing the risk of occult hypoxemia. In the current article, measurements of SpO2 on 17 cyanotic newborns were performed by means of a Nellcor pulse oximeter (POx), based on light with two wavelengths in the red and infrared regions (660 and 900 nm), and by means of a novel POx, based on two wavelengths in the infrared region (761 and 820 nm). The SpO2 readings from the two POxs showed higher values than the invasive SaO2 readings, and the disparity increased with decreasing SaO2. SpO2 measured using the two infrared wavelengths showed better correlation with SaO2 than SpO2 measured using the red and infrared wavelengths. After appropriate calibration, the standard deviation of the individual SpO2-SaO2 differences for the two-infrared POx was smaller (3.6%) than that for the red and infrared POx (6.5%, p < 0.05). The overestimation of SpO2 readings in hypoxemia was explained by the increase in hypoxemia of the optical pathlengths-ratio between the two wavelengths. The two-infrared POx can reduce the overestimation of SpO2 measurement in hypoxemia and the consequent risk of occult hypoxemia, owing to its smaller increase in pathlengths-ratio in hypoxemia.
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Affiliation(s)
- Eyal Elron
- Neonatal Intensive Care Unit, Schneider Children’s Medical Center, Petah Tikva 4920235, Israel
| | - Ruben Bromiker
- Neonatal Intensive Care Unit, Schneider Children’s Medical Center, Petah Tikva 4920235, Israel
- Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv 6997801, Israel
| | | | | | - Ori Goldberg
- Neonatal Intensive Care Unit, Schneider Children’s Medical Center, Petah Tikva 4920235, Israel
- Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv 6997801, Israel
- Pediatric Pulmonology Institute, Schneider Children’s Medical Center, Petach Tikva 4920235, Israel
| | - Itamar Nitzan
- Shaare Zedek Medical Center, Jerusalem 9103102, Israel
- Department of Pediatrics, Hebrew University of Jerusalem Medical School, Jerusalem 9112102, Israel
| | - Meir Nitzan
- Lev Academic Center, Jerusalem 9116001, Israel
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Gunther JE, Jayet B, Sekar SKV, Kainerstorfer JM, Andersson-Engels S. Review of optical methods for fetal monitoring in utero. JOURNAL OF BIOPHOTONICS 2022; 15:e202100343. [PMID: 35285153 DOI: 10.1002/jbio.202100343] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/05/2021] [Revised: 02/15/2022] [Accepted: 03/11/2022] [Indexed: 06/14/2023]
Abstract
The current technology for monitoring fetal wellbeing during child birth is cardiotocography. However, CTG has high false positive rates that lead to unnecessary emergency Cesarean deliveries and false negatives that result in birth injuries. To curtail these issues, fetal pulse oximetery has been a topic of interest for many decades. Fetal pulse oximetry would yield the oxygen saturation of the fetus in utero and provide a more robust marker for clinicians to make decisions about performing emergency Cesarean deliveries. Here, we present a review of biomedical optical developments related to transabdominal fetal pulse oximetery in the biophotonics field and the challenges that must be overcome to make transabdominal pulse oximetry a clinical reality.
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Affiliation(s)
| | - Baptiste Jayet
- Tyndall National Institute, University College Cork, Cork, Ireland
| | | | - Jana M Kainerstorfer
- Department of Biomedical Engineering, Carnegie Mellon University, Pennsylvania, USA
| | - Stefan Andersson-Engels
- Tyndall National Institute, University College Cork, Cork, Ireland
- Department of Physics, University College Cork, Cork, Ireland
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8
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Vali K, Kasap B, Qian W, Vafi A, Saffarpour M, Ghiasi S. Estimation of Fetal Blood Oxygen Saturation from Transabdominally Acquired Photoplethysmogram Waveforms . ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2021; 2021:1100-1103. [PMID: 34891479 DOI: 10.1109/embc46164.2021.9629515] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Transabdominal Fetal Pulse Oximetry (TFO) faces several challenges, including the acquisition of noisy Photoplethysmogram (PPG) signals that contain a mixture of maternal and weak fetal information and scarcity of the data points on which an estimation model can be calibrated. This paper presents a novel algorithm that addresses these problems and contributes to the estimation of fetal blood oxygen saturation from PPG signals sensed through the maternal abdomen in a non-invasive manner. Our approach is composed of two critical steps. First, we develop methods to approximate the contribution of pulsating and non-pulsating fetal tissue from the sensed mixed signal. Furthermore, we leverage prior information about the system under observation, such as the physiological plausibility of fetal SpO2 estimates, to mitigate measurement noise and infer additional data samples, enabling improvements in the inferred SpO2 estimation model. We have validated our approach in-vivo, using a pregnant sheep model with a hypoxic fetal lamb. Compared with gold standard SaO2 obtained from blood gas analysis, our fetal SpO2 estimation algorithm yields the cross-validation mean absolute error (MAE) of 6.29% and correlation factor of r=0.82.
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9
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Kasap B, Vali K, Qian W, Chak WH, Vafi A, Saito N, Ghiasi S. Multi-Detector Heart Rate Extraction Method for Transabdominal Fetal Pulse Oximetry . ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2021; 2021:1072-1075. [PMID: 34891473 PMCID: PMC10631454 DOI: 10.1109/embc46164.2021.9630946] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Intrapartum fetal well-being assessment relies on fetal heart rate (FHR) monitoring. Studies have shown that FHR monitoring has a high false-positive rate for detecting fetal hypoxia during labor and delivery. A transabdominal fetal pulse oximeter device that measures fetal oxygen saturation non-invasively through NIR light source and photodetectors could increase the accuracy of hypoxia detection. As light travels through both maternal and fetal tissue, photodetectors on the surface of mother's abdomen capture mixed signals comprising fetal and maternal information. The fetal information should be extracted first to enable fetal oxygen saturation calculation. A multi-detector fetal signal extraction method is presented in this paper where adaptive noise cancellation is applied to four mixed signals captured by four separate photodetectors placed at varying distances from the light source. As a result of adaptive noise cancellation, we obtain four separate FHR by peak detection. Weighting, outlier rejection and averaging are applied to these four fetal heart rates and a mean FHR is reported. The method is evaluated in utero on data collected from hypoxic lamb model. Ground truth for FHR is measured through hemodynamics. The results showed that using multi-detector fetal signal extraction gave up to 18.56% lower root-mean-square FHR error, and up to 57.87% lower maximum absolute FHR error compared to single-detector fetal signal extraction.
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10
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Gunther J, Jayet B, Jacobs A, Burke R, Kainerstorfer JM, Andersson-Engels S. Effect of the presence of amniotic fluid for optical transabdominal fetal monitoring using Monte Carlo simulations. JOURNAL OF BIOPHOTONICS 2021; 14:e202000486. [PMID: 34110703 DOI: 10.1002/jbio.202000486] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/09/2020] [Revised: 05/27/2021] [Accepted: 05/30/2021] [Indexed: 06/12/2023]
Abstract
About a third of babies are delivered by Cesarean section. There has been an increase in maternal deaths during labor due to complications with subsequent births after a C-section. Therefore, there is a clinical motivation to reduce the C-section rate. Current techniques are, however, inefficient at determining fetal distress leading to a high false positive rate for complications and ultimately a C-section. For the current study, Monte Carlo simulations were used to calculate the amount of signal received on a model of a pregnant mother, as well as, the percent of the signal that comes from the fetal layer. Models with and without a 1 mm amniotic fluid were compared and showed differing trends.
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Affiliation(s)
| | - Baptiste Jayet
- Biophotonics@Tyndall, IPIC, Tyndall National Institute, Cork, Ireland
| | - Adam Jacobs
- Sunrise Labs, Inc., Bedford, New Hampshire, USA
| | - Ray Burke
- Biophotonics@Tyndall, IPIC, Tyndall National Institute, Cork, Ireland
| | - Jana M Kainerstorfer
- Department of Biomedical Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania, USA
| | - Stefan Andersson-Engels
- Biophotonics@Tyndall, IPIC, Tyndall National Institute, Cork, Ireland
- Department of Physics, University College Cork, Cork, Ireland
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Kasap B, Vali K, Qian W, Hedriana HL, Wang A, Farmer DL, Ghiasi S. Towards Noninvasive Accurate Detection of Intrapartum Fetal Hypoxic Distress. ... INTERNATIONAL CONFERENCE ON WEARABLE AND IMPLANTABLE BODY SENSOR NETWORKS. INTERNATIONAL CONFERENCE ON WEARABLE AND IMPLANTABLE BODY SENSOR NETWORKS 2021; 2021:10.1109/bsn51625.2021.9507036. [PMID: 37946733 PMCID: PMC10634358 DOI: 10.1109/bsn51625.2021.9507036] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/12/2023]
Abstract
Current intrapartum fetal well-being assessment is performed using electronic fetal monitoring (EFM), technically referred to as cardiotocography (CTG), which transabdominally monitors fetal heart rate (FHR) in relationship to maternal uterine contractions. Sometimes the deceleration in FHR following a uterine contraction can be sign of fetal hypoxic distress, but it may also be a normal physiological response. Multiple studies have shown that EFM has a high false positive rate for detecting fetal hypoxia. This has caused a rise in emergency Cesarean section (C-section) deliveries performed in the US over the years, while the rates of various conditions associated with anoxic brain injury at birth remain unchanged. The underlying problem is that many factors other than hypoxia can cause non-reassuring CTG traces and a more objective measure of oxygen supply to the fetal brain is not conveniently available. We are working to develop a transabdominal fetal pulse oximetry (TFO) system to non-invasively measure fetal arterial blood oxygen saturation (FSpO2) in order to enhance intrapartum fetal monitoring. This paper gives an overview of the past and ongoing work performed to develop TFO, highlights the main engineering and clinical challenges faced and presents preliminary results that demonstrate feasibility of TFO in both pregnant sheep models and human subjects.
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Affiliation(s)
- Begum Kasap
- Electrical and Computer Engineering Department, University of California Davis, Davis, CA, 95616 USA
| | - Kourosh Vali
- Electrical and Computer Engineering Department, University of California Davis, Davis, CA, 95616 USA
| | - Weitai Qian
- Electrical and Computer Engineering Department, University of California Davis, Davis, CA, 95616 USA
| | - Herman L Hedriana
- Department of Obstetrics and Gynecology, University of California Davis Health
| | - Aijun Wang
- Department of Surgery, University of California Davis Health
| | - Diana L Farmer
- Department of Surgery, University of California Davis Health
| | - Soheil Ghiasi
- Electrical and Computer Engineering Department, University of California Davis, Davis, CA, 95616 USA
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12
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Fong DD, Yamashiro KJ, Vali K, Galganski LA, Thies J, Moeinzadeh R, Pivetti C, Knoesen A, Srinivasan VJ, Hedriana HL, Farmer DL, Johnson MA, Ghiasi S. Design and In Vivo Evaluation of a Non-Invasive Transabdominal Fetal Pulse Oximeter. IEEE Trans Biomed Eng 2020; 68:256-266. [PMID: 32746021 DOI: 10.1109/tbme.2020.3000977] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
OBJECTIVE Current intrapartum fetal monitoring technology is unable to provide physicians with an objective metric of fetal well-being, leading to degraded patient outcomes and increased litigation costs. Fetal oxygen saturation (SpO2) is a more suitable measure of fetal distress, but the inaccessibility of the fetus prior to birth makes this impossible to capture through current means. In this paper, we present a fully non-invasive, transabdominal fetal oximetry (TFO) system that provides in utero measures of fetal SpO2. METHODS TFO is performed by placing a reflectance-mode optode on the maternal abdomen and sending photons into the body to investigate the underlying fetal tissue. The proposed TFO system design consists of a multi-detector optode, an embedded optode control system, and custom user-interface software. To evaluate the developed TFO system, we utilized an in utero hypoxic fetal lamb model and performed controlled desaturation experiments while capturing gold standard arterial blood gases (SaO2). RESULTS Various degrees of fetal hypoxia were induced with true SaO2 values ranging between 10.5% and 66%. The non-invasive TFO system was able to accurately measure these fetal SpO2 values, supported by a root mean-squared error of 6.37% and strong measures of agreement with the gold standard. CONCLUSION The results support the efficacy of the presented TFO system to non-invasively measure a wide-range of fetal SpO2 values and identify critical levels of fetal hypoxia. SIGNIFICANCE TFO has the potential to improve fetal outcomes by providing obstetricians with a non-invasive measure of fetal oxygen saturation prior to delivery.
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13
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Nitzan M, Nitzan I, Arieli Y. The Various Oximetric Techniques Used for the Evaluation of Blood Oxygenation. SENSORS 2020; 20:s20174844. [PMID: 32867184 PMCID: PMC7506757 DOI: 10.3390/s20174844] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/05/2020] [Revised: 08/24/2020] [Accepted: 08/25/2020] [Indexed: 12/12/2022]
Abstract
Adequate oxygen delivery to a tissue depends on sufficient oxygen content in arterial blood and blood flow to the tissue. Oximetry is a technique for the assessment of blood oxygenation by measurements of light transmission through the blood, which is based on the different absorption spectra of oxygenated and deoxygenated hemoglobin. Oxygen saturation in arterial blood provides information on the adequacy of respiration and is routinely measured in clinical settings, utilizing pulse oximetry. Oxygen saturation, in venous blood (SvO2) and in the entire blood in a tissue (StO2), is related to the blood supply to the tissue, and several oximetric techniques have been developed for their assessment. SvO2 can be measured non-invasively in the fingers, making use of modified pulse oximetry, and in the retina, using the modified Beer–Lambert Law. StO2 is measured in peripheral muscle and cerebral tissue by means of various modes of near infrared spectroscopy (NIRS), utilizing the relative transparency of infrared light in muscle and cerebral tissue. The primary problem of oximetry is the discrimination between absorption by hemoglobin and scattering by tissue elements in the attenuation measurement, and the various techniques developed for isolating the absorption effect are presented in the current review, with their limitations.
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Affiliation(s)
- Meir Nitzan
- Department of Physics/Electro-Optics Engineering, Jerusalem College of Technology, 21 Havaad Haleumi St., Jerusalem 91160, Israel;
- Correspondence:
| | - Itamar Nitzan
- Monash Newborn, Monash Children’s Hospital, Melbourne 3168, Australia;
- Department of Neonatology, Shaare Zedek Medical Center, Shmuel Bait St 12, Jerusalem 9103102, Israel
| | - Yoel Arieli
- Department of Physics/Electro-Optics Engineering, Jerusalem College of Technology, 21 Havaad Haleumi St., Jerusalem 91160, Israel;
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14
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Bottrich M, Laqua D, Husar P. Estimating the Shape of the Fetal Pulse Curve for Transabdominal Pulse Oximetry using Synchronous Averaging . ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2020; 2020:1-4. [PMID: 33017916 DOI: 10.1109/embc44109.2020.9176692] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
A sufficient oxygen supply of the fetus is necessary for a proper development of the organs. Transabdominal fetal pulse oximetry is a method that allows to measure the oxygenation of the fetal blood non-invasively by placing the light sources and photodetectors on the belly of the pregnant woman. The shape of the measured fetal pulse wave is needed to extract parameters for the estimation of the oxygen saturation. This work presents an extension of our previously presented signal processing strategy that allows to extract an average shape of the fetal pulse wave from noisy mixed photoplethysmograms (PPG) with dominating maternal and very weak fetal signal components. An adaptive noise canceller and a comb filter are used to suppress the maternal component. The quality of the resulting fetal signal is sufficient to identify single pulse waves in time domain. Further processing demonstrates the extraction of the mean shape of a single fetal pulse wave by synchronous averaging of several detected pulses. The method is evaluated with different datasets of several simulated and synthetic signals measured with a tissue mimicking phantom. The feasibility of the approach is demonstrated by preparing the mixed PPGs to perform fetal pulse oximetry in future studies. However, clinical measurements are needed to finally evaluate the proposed system beyond synthetic datasets.
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Fong DD, Yamashiro KJ, Johnson MA, Vali K, Galganski LA, Pivetti CD, Farmer DL, Hedriana HL, Ghiasi S. Validation of a Novel Transabdominal Fetal Oximeter in a Hypoxic Fetal Lamb Model. Reprod Sci 2020; 27:1960-1966. [PMID: 32542541 DOI: 10.1007/s43032-020-00215-5] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2020] [Accepted: 05/06/2020] [Indexed: 11/30/2022]
Abstract
Current intrapartum fetal oxygen saturation (SaO2) monitoring methodologies are limited, mostly consisting of fetal heart rate monitoring which is a poor predictor of fetal hypoxia. A newly developed transabdominal fetal oximeter (TFO) may be able to determine fetal SaO2 non-invasively. This study is to validate a novel TFO in determining fetal SaO2 in a hypoxic fetal lamb model. Fetal hypoxia was induced in at-term pregnant ewe by placing an aortic occlusion balloon infrarenally and inflating it in a stepwise fashion to decrease blood flow to the uterine artery. The inflation was held at each step for 10 min, and fetal arterial blood gases (ABGs) were intermittently recorded from the fetal carotid artery. The balloon catheter was deflated when fetal SaO2 fell below 15%, and the fetus was recovered. A total of three desaturation experiments were performed. The average fetal SpO2 reported by the TFO was derived at each hypoxic level and correlated with the ABG measures. Fetal SaO2 from the ABGs ranged from 10.5 to 66%. The TFO SpO2 correlated with the ABG fetal SaO2 (r-squared = 0.856) with no significant differences (p > 0.5). The fetal SpO2 measurements from TFO were significantly different than the maternal SpO2 (p < 0.01), which suggests that the transcutaneous measurements are penetrating through the maternal abdomen sufficiently and are expressing the underlying fetal tissue physiology. The recently developed TFO system was able to non-invasively report the fetal SpO2, which showed strong correlation with ABG measures and showed no significant differences.
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Affiliation(s)
- Daniel D Fong
- Electrical and Computer Engineering, University of California Davis, Davis, CA, USA.
| | - Kaeli J Yamashiro
- Department of Surgery, University of California Davis Health, Sacramento, CA, USA
| | - Michael Austin Johnson
- Department of Emergency Medicine, University of California Davis Health, Sacramento, CA, USA.,Division of Emergency Medicine, Department of Surgery, University of Utah, Salt Lake City, UT, USA
| | - Kourosh Vali
- Electrical and Computer Engineering, University of California Davis, Davis, CA, USA
| | - Laura A Galganski
- Department of Surgery, University of California Davis Health, Sacramento, CA, USA
| | | | - Diana L Farmer
- Department of Surgery, University of California Davis Health, Sacramento, CA, USA
| | - Herman L Hedriana
- Department of Obstetrics and Gynecology, University of California Davis Health, Sacramento, CA, USA
| | - Soheil Ghiasi
- Electrical and Computer Engineering, University of California Davis, Davis, CA, USA
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Bottrich M, Husar P. Extraction of the Fetal Pulse Curve for Transabdominal Pulse Oximetry using Adaptive and Comb Filters .. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2020; 2019:15-18. [PMID: 31945834 DOI: 10.1109/embc.2019.8856292] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
The fetal pulse curve can be captured by placing light sources and detectors on the belly of a pregnant woman. Following the principle of reflection pulse oximetry, the light emitted into the abdomen is modulated by pulsing maternal and fetal arteries. The acquired signal is a mixture of a weak fetal and a dominating maternal photoplethysmogram (PPG). A first step towards estimation of the fetal oxygen level is the reconstruction of the purely fetal signal in time domain. As already shown in a former work, comb filters are well suited for the task, in case the fetal heart rate is known. In this work we extend the method by utilizing an adaptive noise canceller (ANC) to estimate the fetal pulse rate for comb filter design. Synthetic test signals with constant and time variable pulse rates are generated in order to achieve reproducible conditions. The ANC is fed by the mixed PPG and the maternal reference signal to reduce the dominant maternal components. The fetal pulse rate is computed by evaluating peaks in the resulting signal in time and frequency domain. The findings are used for comb filter design. It is shown that the extraction of the fetal pulse curve from the synthetic mixed PPGs by using the proposed strategy is promising. Clinical test measurements are the next step for evaluation.
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Bottrich M, Husar P. Signal Separation for Transabdominal Non-invasive Fetal Pulse Oximetry using Comb Filters. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2019; 2018:5870-5873. [PMID: 30441671 DOI: 10.1109/embc.2018.8513614] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Non-invasive fetal pulse oximetry is the application of reflection pulse oximetry to the abdomen of a pregnant woman. Light sources and detectors areplaced on the belly. Emitted photons travel through maternal and fetal tissue and back to the detectors. The captured photoplethysmogram (PPG) is a complex mixture of the maternal and fetal pulse curve. A purely fetal PPG in time domain is needed to estimate the oxygen level of the unborn child. In this work we describe the application of comb filters to separate the fetalfrom the maternal signal. Finite element simulations and phantom measurements are utilized to generate and measure synthetic signals at different heart rates and noise levels. Comb filters with peak frequencies matched to the fetal heart rate are applied to the mixed PPGs. The filtered signals prove that the extraction of the fetal signal is sufficient even at a distance between the maternal and the fetal signal magnitudes of around 80 dB. The resulting signal quality is sufficient for beat to beat analysis and feature extraction in the time domain. We conclude that comb filtering is a suitable signal separation method for non-invasive fetal pulse oximetry.
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Fong DD, Srinivasan VJ, Vali K, Ghiasi S. Optode Design Space Exploration for Clinically-robust Non-invasive Fetal Oximetry. ACM TRANSACTIONS ON EMBEDDED COMPUTING SYSTEMS : TECS 2019; 18:1-22. [PMID: 34084098 PMCID: PMC8171863 DOI: 10.1145/3358207] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/01/2019] [Accepted: 07/01/2019] [Indexed: 06/11/2023]
Abstract
Non-invasive transabdominal fetal oximetry (TFO) has the potential to improve delivery outcomes by providing physicians with an objective metric of fetal well-being during labor. Fundamentally, the technology is based on sending light through the maternal abdomen to investigate deep fetal tissue, followed by detection and processing of the light that returns (via scattering) to the outside of the maternal abdomen. The placement of the photodetector in relation to the light source critically impacts TFO system performance, including its operational robustness in the face of fetal depth variation. However, anatomical differences between pregnant women cause the fetal depths to vary drastically, which further complicates the optical probe (optode) design optimization. In this paper, we present a methodology to solve this problem. We frame optode design space exploration as a multi-objective optimization problem, where hardware complexity (cost) and performance across a wider patient population (robustness) form competing objectives. We propose a model-based approach to characterize the Pareto-optimal points in the optode design space, through which a specific design is selected. Experimental evaluation via simulation and in vivo measurement on pregnant sheep support the efficacy of our approach.
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Affiliation(s)
- Daniel D Fong
- University of California, Davis, 1 Shields Avenue, Davis, CA, 95616
| | | | - Kourosh Vali
- University of California, Davis, 1 Shields Avenue, Davis, CA, 95616
| | - Soheil Ghiasi
- University of California, Davis, 1 Shields Avenue, Davis, CA, 95616
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Selifonov AA, Tuchin VV. Investigation of the Diffusion of Methylene Blue through Dentin from a Human Tooth. Biophysics (Nagoya-shi) 2019. [DOI: 10.1134/s0006350918060222] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
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20
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Fong DD, Knoesen A, Motamedi M, O'Neill T, Ghiasi S. Recovering the fetal signal in transabdominal fetal pulse oximetry. ACTA ACUST UNITED AC 2018. [DOI: 10.1016/j.smhl.2018.07.011] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
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21
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Böttrich M, Ley S, Husar P. Simulation study on the effect of tissue geometries to fluence composition for non-invasive fetal pulse oximetry. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2016; 2015:5122-5. [PMID: 26737444 DOI: 10.1109/embc.2015.7319544] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Transabdominal fetal pulse oximetry is a method to estimate the state of oxygenation of a fetus in-utero, utilizing the principle of reflection pulse oximetry. The extraction of fetal related information from a mixed fetal-maternal signal is elementary. Minimizing the ratio of purely maternal components of the signal at the detector side obviously facilitates signal separation. In this paper we analyze the influence of tissue geometries to the fluence composition at the surface of the abdomen. Monte-Carlo method is used to compute photon propagation in spherical layered tissue models. Spatial fluence distributions at the surface of the models are visualized and discussed. Our results show the characteristic effects of the distance between the fetus and the surface and the radius of the abdomen to the fluence composition at the detector. Further, the simulations indicate suitable source-detector configurations considering various anatomical conditions. We conclude that an adoption of the source-detector configuration to the individual tissue geometry at hand is necessary to achieve a proper signal composition and quality. Utilizing simulations for sensor design enhances the understanding of photon distributions in complex tissue geometries and supports a successful implementation of transabdominal fetal pulse oximetry.
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22
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Zhang D, Robinson K, Mihai DM, Washington I. Sequestration of ubiquitous dietary derived pigments enables mitochondrial light sensing. Sci Rep 2016; 6:34320. [PMID: 27731322 PMCID: PMC5059631 DOI: 10.1038/srep34320] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2016] [Accepted: 09/09/2016] [Indexed: 12/17/2022] Open
Abstract
Animals alter their physiological states in response to their environment. We show that the introduction of a chlorophyll metabolite, a light-absorbing pigment widely consumed in human diets, to Caenorhabditis elegans results in animals whose fat mass can be modulated by exposure to light, despite the worm consuming the same amount of food. In the presence of the chlorophyll metabolite, exposing the worms to light increased adenosine triphosphate, reduced oxidative damage, and increased median life spans, without an effect on animal reproduction. Mice fed a dietary metabolite of chlorophyll and exposed to light, over several months, showed reductions in systemic inflammation as measured by plasma α-macroglobulin. We propose that dietary chlorophyll metabolites can enable mitochondria to use light as an environmental cue, by absorbing light and transferring the energy to mitochondrial coenzyme Q.
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Affiliation(s)
- Dan Zhang
- Columbia University Medical Center, Ophthalmology, New York, NY 10032, USA
| | - Kiera Robinson
- Columbia University Medical Center, Ophthalmology, New York, NY 10032, USA
| | - Doina M Mihai
- Columbia University Medical Center, Ophthalmology, New York, NY 10032, USA
| | - Ilyas Washington
- Columbia University Medical Center, Ophthalmology, New York, NY 10032, USA
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Böttrich M, Laqua D, Husar P. Principle study on the signal connection at transabdominal fetal pulse oximetry. CURRENT DIRECTIONS IN BIOMEDICAL ENGINEERING 2016. [DOI: 10.1515/cdbme-2016-0144] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Abstract
Transabdominal fetal pulse oximetry is an approach to measure oxygen saturation of the unborn child non-invasively. The principle of pulse oximetry is applied to the abdomen of a pregnant woman, such that the measured signal includes both, the maternal and the fetal pulse curve. One of the major challenges is to extract the shape of the fetal pulse curve from the mixed signal for computation of the oxygen saturation. In this paper we analyze the principle kind of connection of the fetal and maternal pulse curves in the measured signal. A time varying finite element model is used to rebuild the basic measurement environment, including a bulk tissue and two independently pulsing arteries to model the fetal and maternal blood circuit. The distribution of the light fluence rate in the model is computed by applying diffusion equation. From the detectors we extracted the time dependent fluence rate and analyzed the signal regarding its components. The frequency spectra of the signals show peaks at the fetal and maternal basic frequencies. Additional signal components are visible in the spectra, indicating multiplicative coupling of the fetal and maternal pulse curves. We conclude that the underlying signal model of algorithms for robust extraction of the shape of the fetal pulse curve, have to consider additive and multiplicative signal coupling.
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Affiliation(s)
- Marcel Böttrich
- Biosignal Processing Group, Technische Universität Ilmenau, Gustav-Kirchhoff Str. 2, 98693 Ilmenau, Germany
| | - Daniel Laqua
- Biosignal Processing Group, Technische Universität Ilmenau, Gustav-Kirchhoff Str. 2, 98693 Ilmenau, Germany
| | - Peter Husar
- Biosignal Processing Group, Technische Universität Ilmenau, Gustav-Kirchhoff Str. 2, 98693 Ilmenau, Germany
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Leier M, Pilt K, Karai D, Jervan G. Smart photoplethysmographic sensor for pulse wave registration at different vascular depths. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2016; 2015:1849-52. [PMID: 26736641 DOI: 10.1109/embc.2015.7318741] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
The aim of this paper is to propose a smart optical sensor for cardiovascular activity monitoring at different tissue layers. Photoplethysmography (PPG) is a noninvasive optical technique for monitoring mainly blood volume changes in the examined tissue. However, different important physiological parameters, such as oxygen saturation, heart and breathing rate, dynamics of skin micro-circulation, vasomotion activity etc., can be extracted from the registered PPG signal. The developed sensor consists of 32 light emitting sources with four different wavelengths, which are located to the four different distances from four photo detectors. Compared to the existing sensors, the system enables to select the optimal LED (light emitting diode) and photo detector couple in order to obtain the pulse wave signal from the interested blood vessels with the highest possible signal to noise ratio. In this study, the designed PPG sensor was tested for the pulse wave registration from radial artery. The highest efficiency and signal to noise ratio was achieved using infrared LED (940 nm) and photo-diode pair.
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25
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Laqua D, Pollnow S, Fischer J, Ley S, Husar P. A phantom with pulsating artificial vessels for non-invasive fetal pulse oximetry. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2015; 2014:5631-4. [PMID: 25571272 DOI: 10.1109/embc.2014.6944904] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Arterial oxygen saturation of the fetus is an important parameter for monitoring its physical condition. During labor and delivery the transabdominal non-invasive fetal pulse oximetry could minimize the risk for mother and fetus, compared to other existing invasive examination methods. In this contribution, we developed a physical-like phantom to investigate new sensor circuits and algorithms of a non-invasive diagnostic method for fetal pulse oximetry. Hence, the developed artificial vascular system consists of two independent tube systems representing the maternal and fetal vessel system. The arterial blood pressure is reproduced with a pre-pressure and an artificial vascular system. Each pulse wave can be reproduced, by digital control of a proportional valve, adjustable viscoelastic elements, and resistances. The measurements are performed by pressure transducers, optical sensor units, and a coplanar capacitive sensor. Transmission and reflection measurements have shown that the fetal and maternal pulse waves can be reproduced qualitatively. The measured light represents the transabdominal modulated signal on an abdomen of a pregnant woman.
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Böttrich M, Ley S, Husar P. Simulation based investigation of source-detector configurations for non-invasive fetal pulse oximetry. CURRENT DIRECTIONS IN BIOMEDICAL ENGINEERING 2015. [DOI: 10.1515/cdbme-2015-0108] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
AbstractTransabdominal fetal pulse oximetry is a method to monitor the oxygen supply of the unborn child non-invasively. Due to the measurement setup, the received signal of the detector is composed of photons coding purely maternal and photons coding mixed fetal-maternal information. To analyze the wellbeing of the fetus, the fetal signal is extracted from the mixed component. In this paper we assess source-detector configurations, such that the mixed fetal-maternal components of the acquired signals are maximized. Monte-Carlo method is used to simulate light propagation and photon distribution in tissue. We use a plane layer and a spherical layer geometry to model the abdomen of a pregnant woman. From the simulations we extracted the fluence at the detector side for several source-detector distances and analyzed the ratio of the mixed fluence component to total fluence. Our simulations showed that the power of the mixed component depends on the source-detector distance as expected. Further we were able to visualize hot spot areas in the spherical layer model where the mixed fluence ratio reaches the highest level. The results are of high importance for sensor design considering signal composition and quality for non-invasive fetal pulse oximetry.
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Affiliation(s)
- Marcel Böttrich
- 1Biosignal Processing Group, Technische Universität Ilmenau, Gustav-Kirchhoff Str. 2, 98693 Ilmenau
| | - Sebastian Ley
- 1Biosignal Processing Group, Technische Universität Ilmenau, Gustav-Kirchhoff Str. 2, 98693 Ilmenau
| | - Peter Husar
- 1Biosignal Processing Group, Technische Universität Ilmenau, Gustav-Kirchhoff Str. 2, 98693 Ilmenau
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Yao J, Tian F, Rakvongthai Y, Oraintara S, Liu H. Quantification and normalization of noise variance with sparsity regularization to enhance diffuse optical tomography. BIOMEDICAL OPTICS EXPRESS 2015; 6:2961-79. [PMID: 26309760 PMCID: PMC4541524 DOI: 10.1364/boe.6.002961] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/09/2015] [Revised: 07/12/2015] [Accepted: 07/15/2015] [Indexed: 05/21/2023]
Abstract
Conventional reconstruction of diffuse optical tomography (DOT) is based on the Tikhonov regularization and the white Gaussian noise assumption. Consequently, the reconstructed DOT images usually have a low spatial resolution. In this work, we have derived a novel quantification method for noise variance based on the linear Rytov approximation of the photon diffusion equation. Specifically, we have implemented this quantification of noise variance to normalize the measurement signals from all source-detector channels along with sparsity regularization to provide high-quality DOT images. Multiple experiments from computer simulations and laboratory phantoms were performed to validate and support the newly developed algorithm. The reconstructed images demonstrate that quantification and normalization of noise variance with sparsity regularization (QNNVSR) is an effective reconstruction approach to greatly enhance the spatial resolution and the shape fidelity for DOT images. Since noise variance can be estimated by our derived expression with relatively limited resources available, this approach is practically useful for many DOT applications.
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Affiliation(s)
- Jixing Yao
- Department of Electrical Engineering, University of Texas at Arlington, Arlington, TX 76019 USA
| | - Fenghua Tian
- Department of Bioengineering, University of Texas at Arlington, Arlington, TX 76019 USA
| | - Yothin Rakvongthai
- Division of Nuclear Medicine and Molecular Imaging, Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Boston, MA 02114 USA
| | - Soontorn Oraintara
- Department of Electrical Engineering, University of Texas at Arlington, Arlington, TX 76019 USA
| | - Hanli Liu
- Department of Bioengineering, University of Texas at Arlington, Arlington, TX 76019 USA
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28
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Liu H, Ivanov K, Wang Y, Wang L. A novel method based on two cameras for accurate estimation of arterial oxygen saturation. Biomed Eng Online 2015; 14:52. [PMID: 26025439 PMCID: PMC4449570 DOI: 10.1186/s12938-015-0045-1] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2014] [Accepted: 05/01/2015] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Photoplethysmographic imaging (PPGi) that is based on camera allows acquiring photoplethysmogram and measuring physiological parameters such as pulse rate, respiration rate and perfusion level. It has also shown potential for estimation of arterial oxygen saturation (SaO2). However, there are some technical limitations such as optical shunting, different camera sensitivity to different light spectra, different AC-to-DC ratios (the peak-to-peak amplitude to baseline ratio) of the PPGi signal for different portions of the sensor surface area, the low sampling rate and the inconsistency of contact force between the fingertip and camera lens. METHODS In this paper, we take full account of the above-mentioned design challenges and present an accurate SaO2 estimation method based on two cameras. The hardware system we used consisted of an FPGA development board (XC6SLX150T-3FGG676 from Xilinx), with connected to it two commercial cameras and an SD card. The two cameras were placed back to back, one camera acquired PPGi signal from the right index fingertip under 660 nm light illumination while the other camera acquired PPGi signal from the thumb fingertip using an 800 nm light illumination. The both PPGi signals were captured simultaneously, recorded in a text file on the SD card and processed offline using MATLAB®. The calculation of SaO2 was based on the principle of pulse oximetry. The AC-to-DC ratio was acquired by the ratio of powers of AC and DC components of the PPGi signal in the time-frequency domain using the smoothed pseudo Wigner-Ville distribution. The calibration curve required for SaO2 measurement was obtained by linear regression analysis. RESULTS The results of our estimation method from 12 subjects showed a high correlation and accuracy with those of conventional pulse oximetry for the range from 90 to 100%. CONCLUSIONS Our method is suitable for mobile applications implemented in smartphones, which could allow SaO2 measurement in a pervasive environment.
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Affiliation(s)
- He Liu
- Biomedical Engineering Department, Harbin Institute of Technology, Harbin, 150001, China.
- Shenzhen Key Laboratory for Low-cost Healthcare, Key Lab for Health Informatics, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Xueyuan Avenue 1068, Shenzhen, 518055, China..
| | - Kamen Ivanov
- Shenzhen Key Laboratory for Low-cost Healthcare, Key Lab for Health Informatics, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Xueyuan Avenue 1068, Shenzhen, 518055, China..
| | - Yadong Wang
- Biomedical Engineering Department, Harbin Institute of Technology, Harbin, 150001, China.
| | - Lei Wang
- Shenzhen Key Laboratory for Low-cost Healthcare, Key Lab for Health Informatics, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Xueyuan Avenue 1068, Shenzhen, 518055, China..
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Grabtchak S, Montgomery LG, Pang B, Wang Y, Zhang C, Li Z, Xia Y, Whelan WM. Interstitial diffuse radiance spectroscopy of gold nanocages and nanorods in bulk muscle tissues. Int J Nanomedicine 2015; 10:1307-20. [PMID: 25709450 PMCID: PMC4335609 DOI: 10.2147/ijn.s79246] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Radiance spectroscopy was applied to the interstitial detection of localized inclusions containing Au nanocages or nanorods with various concentrations embedded in porcine muscle phantoms. The radiance was quantified using a perturbation approach, which enabled the separation of contributions from the porcine phantom and the localized inclusion, with the inclusion serving as a perturbation probe of photon distributions in the turbid medium. Positioning the inclusion at various places in the phantom allowed for tracking of photons that originated from a light source, passed through the inclusion's location, and reached a detector. The inclusions with high extinction coefficients were able to absorb nearly all photons in the range of 650-900 nm, leading to a spectrally flat radiance signal. This signal could be converted to the relative density of photons incident on the inclusion. Finally, the experimentally measured quantities were expressed via the relative perturbation and arranged into the classical Beer-Lambert law that allowed one to extract the extinction coefficients of various types of Au nanoparticles in both the transmission and back reflection geometries. It was shown that the spatial variation of perturbation could be described as 1/r dependence, where r is the distance between the inclusion and the detector. Due to a larger absorption cross section, Au nanocages produced greater perturbations than Au nanorods of equal particle concentration, indicating a better suitability of Au nanocages as contrast agents for optical measurements in turbid media. Individual measurements from different inclusions were combined into detectability maps.
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Affiliation(s)
- Serge Grabtchak
- Department of Physics, University of Prince Edward Island, Charlottetown, PEI, Canada
- Departments of Electrical and Computer Engineering, and Physics, Dalhousie University, Halifax, Canada
| | - Logan G Montgomery
- Department of Physics, University of Prince Edward Island, Charlottetown, PEI, Canada
| | - Bo Pang
- Department of Biomedical Engineering, Peking University, Beijing, People’s Republic of China
- The Wallace H Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA, USA
| | - Yi Wang
- The Wallace H Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA, USA
- Key Laboratory of Green Synthesis and Applications, College of Chemistry, Chongqing Normal University, Chongqing, People’s Republic of China
| | - Chao Zhang
- Laboratory of Optical Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, People’s Republic of China
- College of Physics and Optoelectronics, South China University of Technology, Guangzhou, People’s Republic of China
| | - Zhiyuan Li
- Laboratory of Optical Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, People’s Republic of China
- College of Physics and Optoelectronics, South China University of Technology, Guangzhou, People’s Republic of China
| | - Younan Xia
- The Wallace H Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA, USA
- School of Chemistry and Biochemistry, and School of Chemical and Biomolecular Engineering, Georgia Institute of Technology, Atlanta, GA, USA
| | - William M Whelan
- Department of Physics, University of Prince Edward Island, Charlottetown, PEI, Canada
- Atlantic Veterinary College, Charlottetown, PEI, Canada
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Kanawade R, Klämpfl F, Riemann M, Knipfer C, Tangermann-Gerk K, Schmidt M, Stelzle F. Novel method for early signs of clinical shock detection by monitoring blood capillary/vessel spatial pattern. JOURNAL OF BIOPHOTONICS 2014; 7:841-849. [PMID: 23843326 DOI: 10.1002/jbio.201300065] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/30/2013] [Revised: 06/24/2013] [Accepted: 06/25/2013] [Indexed: 06/02/2023]
Abstract
The ability to monitor capillary/vessel spatial patterns and local blood volume fractions is critical in clinical shock detection and its prevention in Intensive Care Units (ICU). Although the causes of shock might be different, the basic abnormalities in pathophysiological changes are the same. To detect these changes, we have developed a novel method based on both spectrally and spatially resolved diffuse reflectance spectra. The preliminary study has shown that this method can monitor the spatial distribution of capillary/vessel spatial patterns through local blood volume fractions of reduced hemoglobin and oxyhemoglobin. This method can be used as a real-time and non-invasive tool for the monitoring of shock development and feedback on the therapeutic intervention.
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Affiliation(s)
- Rajesh Kanawade
- Clinical Photonics Lab., Erlangen Graduate School in Advanced Optical Technologies SAOT, Friedrich-Alexander-Universität Erlangen-Nürnberg, Paul-Gordan-Straße 6, 91052 Erlangen, Germany; Institute of Photonic Technologies, Friedrich-Alexander-Universität Erlangen-Nürnberg, Paul-Gordan-Straße 3, 91052 Erlangen, Germany.
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Nitzan M, Romem A, Koppel R. Pulse oximetry: fundamentals and technology update. MEDICAL DEVICES-EVIDENCE AND RESEARCH 2014; 7:231-9. [PMID: 25031547 PMCID: PMC4099100 DOI: 10.2147/mder.s47319] [Citation(s) in RCA: 143] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
Oxygen saturation in the arterial blood (SaO2) provides information on the adequacy of respiratory function. SaO2 can be assessed noninvasively by pulse oximetry, which is based on photoplethysmographic pulses in two wavelengths, generally in the red and infrared regions. The calibration of the measured photoplethysmographic signals is performed empirically for each type of commercial pulse-oximeter sensor, utilizing in vitro measurement of SaO2 in extracted arterial blood by means of co-oximetry. Due to the discrepancy between the measurement of SaO2 by pulse oximetry and the invasive technique, the former is denoted as SpO2. Manufacturers of pulse oximeters generally claim an accuracy of 2%, evaluated by the standard deviation (SD) of the differences between SpO2 and SaO2, measured simultaneously in healthy subjects. However, an SD of 2% reflects an expected error of 4% (two SDs) or more in 5% of the examinations, which is in accordance with an error of 3%–4%, reported in clinical studies. This level of accuracy is sufficient for the detection of a significant decline in respiratory function in patients, and pulse oximetry has been accepted as a reliable technique for that purpose. The accuracy of SpO2 measurement is insufficient in several situations, such as critically ill patients receiving supplemental oxygen, and can be hazardous if it leads to elevated values of oxygen partial pressure in blood. In particular, preterm newborns are vulnerable to retinopathy of prematurity induced by high oxygen concentration in the blood. The low accuracy of SpO2 measurement in critically ill patients and newborns can be attributed to the empirical calibration process, which is performed on healthy volunteers. Other limitations of pulse oximetry include the presence of dyshemoglobins, which has been addressed by multiwavelength pulse oximetry, as well as low perfusion and motion artifacts that are partially rectified by sophisticated algorithms and also by reflection pulse oximetry.
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Affiliation(s)
- Meir Nitzan
- Department of Physics/Electro-Optics, Jerusalem College of Technology, Jerusalem, Israel
| | - Ayal Romem
- Pulmonary Institute, Shaare Zedek Medical Center, Jerusalem, Israel
| | - Robert Koppel
- Neonatal/Perinatal Medicine, Cohen Children's Medical Center of New York/North Shore-LIJ Health System, New Hyde Park, NY, United States
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Nitzan M, Noach S, Tobal E, Adar Y, Miller Y, Shalom E, Engelberg S. Calibration-free pulse oximetry based on two wavelengths in the infrared - a preliminary study. SENSORS 2014; 14:7420-34. [PMID: 24763216 PMCID: PMC4029673 DOI: 10.3390/s140407420] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/23/2014] [Revised: 04/09/2014] [Accepted: 04/14/2014] [Indexed: 11/21/2022]
Abstract
The assessment of oxygen saturation in arterial blood by pulse oximetry (SpO2) is based on the different light absorption spectra for oxygenated and deoxygenated hemoglobin and the analysis of photoplethysmographic (PPG) signals acquired at two wavelengths. Commercial pulse oximeters use two wavelengths in the red and infrared regions which have different pathlengths and the relationship between the PPG-derived parameters and oxygen saturation in arterial blood is determined by means of an empirical calibration. This calibration results in an inherent error, and pulse oximetry thus has an error of about 4%, which is too high for some clinical problems. We present calibration-free pulse oximetry for measurement of SpO2, based on PPG pulses of two nearby wavelengths in the infrared. By neglecting the difference between the path-lengths of the two nearby wavelengths, SpO2 can be derived from the PPG parameters with no need for calibration. In the current study we used three laser diodes of wavelengths 780, 785 and 808 nm, with narrow spectral line-width. SaO2 was calculated by using each pair of PPG signals selected from the three wavelengths. In measurements on healthy subjects, SpO2 values, obtained by the 780–808 nm wavelength pair were found to be in the normal range. The measurement of SpO2 by two nearby wavelengths in the infrared with narrow line-width enables the assessment of SpO2 without calibration.
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Affiliation(s)
- Meir Nitzan
- Department of Applied Physics/Medical Engineering, Jerusalem College of Technology, Jerusalem 9116001, Israel.
| | - Salman Noach
- Department of Applied Physics/Medical Engineering, Jerusalem College of Technology, Jerusalem 9116001, Israel.
| | - Elias Tobal
- Department of Applied Physics/Medical Engineering, Jerusalem College of Technology, Jerusalem 9116001, Israel.
| | - Yair Adar
- Department of Applied Physics/Medical Engineering, Jerusalem College of Technology, Jerusalem 9116001, Israel.
| | - Yaacov Miller
- Department of Applied Physics/Medical Engineering, Jerusalem College of Technology, Jerusalem 9116001, Israel.
| | - Eran Shalom
- Department of Applied Physics/Medical Engineering, Jerusalem College of Technology, Jerusalem 9116001, Israel.
| | - Shlomo Engelberg
- Department of Electronics, Jerusalem College of Technology, Jerusalem 9116001, Israel.
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Oweis RJ, As'ad H, Aldarawsheh A, Al-Khdeirat R, Lwissy K. A PC-aided optical foetal heart rate detection system. J Med Eng Technol 2013; 38:23-31. [PMID: 24195701 DOI: 10.3109/03091902.2013.849299] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Safe monitoring of foetal heart rate is a valuable tool for the healthy evolution and wellbeing of both foetus and mother. This paper presents a non-invasive optical technique that allows for foetal heart rate detection using a photovoltaic infrared (IR) detector placed on the mother's abdomen. The system presented here consists of a photoplethysmography (PPG) circuit, abdomen circuit and a personal computer equipped with MATLAB. A near IR beam having a wavelength of 880 nm is transmitted through the mother's abdomen and foetal tissue. The received abdominal signal that conveys information pertaining to the mother and foetal heart rate is sensed by a low noise photodetector. The PC receives the signal through the National Instrumentation Data Acquisition Card (NIDAQ). After synchronous detection of the abdominal and finger PPG signals, the designed MATLAB-based software saves, analyses and extracts information related to the foetal heart rate. Extraction is carried out using recursive least squares adaptive filtration. Measurements on eight pregnant women with gestational periods ranging from 35-39 weeks were performed using the proposed system and CTG. Results show a correlation coefficient of 0.978 and a correlation confidence interval between 88-99.6%. The t test results in a p value of 0.034, which is less than 0.05. Low power, low cost, high signal-to-noise ratio, reduction of ambient light effect and ease of use are the main characteristics of the proposed system.
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Affiliation(s)
- Rami J Oweis
- Biomedical Engineering Department, Faculty of Engineering, Jordan University of Science and Technology , PO Box 3030, Irbid 22110 , Jordan
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Xu C, Zhang J, Mihai DM, Washington I. Light-harvesting chlorophyll pigments enable mammalian mitochondria to capture photonic energy and produce ATP. J Cell Sci 2013; 127:388-99. [PMID: 24198392 DOI: 10.1242/jcs.134262] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Sunlight is the most abundant energy source on this planet. However, the ability to convert sunlight into biological energy in the form of adenosine-5'-triphosphate (ATP) is thought to be limited to chlorophyll-containing chloroplasts in photosynthetic organisms. Here we show that mammalian mitochondria can also capture light and synthesize ATP when mixed with a light-capturing metabolite of chlorophyll. The same metabolite fed to the worm Caenorhabditis elegans leads to increase in ATP synthesis upon light exposure, along with an increase in life span. We further demonstrate the same potential to convert light into energy exists in mammals, as chlorophyll metabolites accumulate in mice, rats and swine when fed a chlorophyll-rich diet. Results suggest chlorophyll type molecules modulate mitochondrial ATP by catalyzing the reduction of coenzyme Q, a slow step in mitochondrial ATP synthesis. We propose that through consumption of plant chlorophyll pigments, animals, too, are able to derive energy directly from sunlight.
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Affiliation(s)
- Chen Xu
- Columbia University Medical Center, Ophthalmology, New York, NY 10032, USA
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Cao Q, Zhegalova NG, Wang ST, Akers WJ, Berezin MY. Multispectral imaging in the extended near-infrared window based on endogenous chromophores. JOURNAL OF BIOMEDICAL OPTICS 2013; 18:101318. [PMID: 23933967 PMCID: PMC3739874 DOI: 10.1117/1.jbo.18.10.101318] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/02/2013] [Revised: 05/21/2013] [Accepted: 07/08/2013] [Indexed: 05/19/2023]
Abstract
To minimize the problem with scattering in deep tissues while increasing the penetration depth, we explored the feasibility of imaging in the relatively unexplored extended near infrared (exNIR) spectral region at 900 to 1400 nm with endogenous chromophores. This region, also known as the second NIR window, is weakly dominated by absorption from water and lipids and is free from other endogenous chromophores with virtually no autofluorescence. To demonstrate the applicability of the exNIR for bioimaging, we analyzed the optical properties of individual components and biological tissues using an InGaAs spectrophotometer and a multispectral InGaAs scanning imager featuring transmission geometry. Based on the differences in spectral properties of tissues, we utilized ratiometric approaches to extract spectral characteristics from the acquired three-dimensional "datacube". The obtained images of an exNIR transmission through a mouse head revealed sufficient details consistent with anatomical structures.
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Affiliation(s)
- Qian Cao
- Washington University School of Medicine, Department of Radiology, St. Louis, Missouri 63110
| | - Natalia G. Zhegalova
- Washington University School of Medicine, Department of Radiology, St. Louis, Missouri 63110
| | - Steven T. Wang
- Washington University School of Medicine, Department of Radiology, St. Louis, Missouri 63110
| | - Walter J. Akers
- Washington University School of Medicine, Department of Radiology, St. Louis, Missouri 63110
| | - Mikhail Y. Berezin
- Washington University School of Medicine, Department of Radiology, St. Louis, Missouri 63110
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36
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Grabtchak S, Palmer TJ, Vitkin IA, Whelan WM. Radiance detection of non-scattering inclusions in turbid media. BIOMEDICAL OPTICS EXPRESS 2012; 3:3001-11. [PMID: 23162735 PMCID: PMC3493233 DOI: 10.1364/boe.3.003001] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/13/2012] [Revised: 10/24/2012] [Accepted: 10/25/2012] [Indexed: 05/10/2023]
Abstract
Detection of non-scattering domains (voids) is an area of active research in biomedical optics. To avoid complexities of image reconstruction algorithms and requirements of a priori knowledge of void locations inherent to diffuse optical tomography (DOT), it would be useful to establish specific experimental signatures of voids that would help identify and detect them by other means. To address this, we present a radiance-based spectro-angular mapping approach that identifies void locations in the angular domain and establishes their spectral features. Using water-filled capillaries in scattering Intralipid as a test platform, we demonstrate perturbations in the directional photon density distribution produced by individual voids.
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Affiliation(s)
- Serge Grabtchak
- Department of Physics, University of Prince Edward Island, Charlottetown, PEI, Canada
- Departments of Electrical and Computer Engineering, and Physics, Dalhousie University, Halifax, NS, Canada
| | - Tyler J. Palmer
- Department of Physics, University of Prince Edward Island, Charlottetown, PEI, Canada
| | - I. Alex Vitkin
- Departments of Medical Biophysics and Radiation Oncology, University of Toronto and Ontario Cancer Institute/University Health Network, Toronto, ON, Canada
| | - William M. Whelan
- Department of Physics, University of Prince Edward Island, Charlottetown, PEI, Canada
- Atlantic Veterinary College, Charlottetown, PEI, Canada
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37
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Kanawade R, Stelzle F, Schmidt M. In Vivo Monitoring of Hemodynamic Changes during Clogging and Unclogging of Blood Supply for the Application of Clinical Shock Detection. ACTA ACUST UNITED AC 2012. [DOI: 10.1016/j.phpro.2012.10.106] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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A technique based on laser Doppler flowmetry and photoplethysmography for simultaneously monitoring blood flow at different tissue depths. Med Biol Eng Comput 2010; 48:415-22. [PMID: 20107915 DOI: 10.1007/s11517-010-0577-2] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2009] [Accepted: 01/11/2010] [Indexed: 10/19/2022]
Abstract
The aim of this study was to validate a non-invasive optical probe for simultaneous blood flow measurement at different vascular depths combining three photoplethysmography (PPG) channels and laser Doppler flowmeter (LDF). Wavelengths of the PPG were near-infrared 810 nm with source-to-detector separation of 10 and 25 mm, and green 560 nm with source-to-detector separation of 4 mm. The probe is intended for clinical studies of pressure ulcer aetiology. The probe was placed over the trapezius muscle, and depths from the skin to the trapezius muscle were measured using ultrasound and varied between 3.8 and 23 mm in the 11 subjects included. A provocation procedure inducing a local enhancement of blood flow in the trapezius muscle was used. Blood flows at rest and post-exercise were compared. It can be concluded that this probe is useful as a tool for discriminating between blood flows at different vascular tissue depths. The vascular depths reached for the different channels in this study were at least 23 mm for the near-infrared PPG channel (source-to-detector separation 25 mm), 10-15 mm for the near-infrared PPG channel (separation 10 mm), and shallower than 4 mm for both the green PPG channel (separation 4 mm) and LDF.
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39
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40
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Kok Beng Gan, Zahedi E, Ali M. Transabdominal Fetal Heart Rate Detection Using NIR Photopleythysmography: Instrumentation and Clinical Results. IEEE Trans Biomed Eng 2009; 56:2075-82. [DOI: 10.1109/tbme.2009.2021578] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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41
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Nioka S, Izzetoglu M, Mawn T, Nijland MJ, Boas D, Chance B. Fetal transabdominal pulse oximeter studies using a hypoxic sheep model. J Matern Fetal Neonatal Med 2009; 17:393-9. [PMID: 16009642 DOI: 10.1080/14767050500123657] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
OBJECTIVE This study investigates the validity of transabdominal pulse oximetry using a sheep fetal hypoxia model with fetal arterial hemoglobin saturation. METHODS Four pregnant ewes were anaesthetized and cannulated through the brachial artery to measure direct arterial blood saturation, SaO(2). Next, the transabdominal pulse oximeter was used to measure indirect measurement of the arterial saturation of the fetus, SpO(2), from the maternal abdomen. Hypoxia was induced by a balloon placed in the maternal aorta. RESULTS There is a linear relationship between SaO(2), arterial blood saturation values of the fetus, and SpO(2), the values measured by the transabdominal pulse oximetry with a slope of 0.75 (r(2)=0.76). CONCLUSION This information can be used to calibrate the transabdominal pulse oximeter as a measurement of fetal arterial saturation. With these results, we can advance the accurate, no-risk, noninvasive transabdominal fetal pulse oximeter for human use. This research may contribute to the more accurate diagnosis of the diseases of the fetus including Hypoxic Ischemic Encephalopathy.
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Affiliation(s)
- Shoko Nioka
- Department of Biochem/Biophysics, University of Pennsylvania, PA 19104, USA.
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Foo JYA, Lim CS, Wilson SJ. Photoplethysmographic assessment of hemodynamic variations using pulsatile tissue blood volume. Angiology 2008; 59:745-52. [PMID: 18388056 DOI: 10.1177/0003319708314245] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Sympathetic responses to provocative tests have shown to provide an early prognosis of abnormalities in the human autonomic nervous system. Photoplethysmographic signal characteristics have been studied to identify vascular diseases. However, knowledge about the pulse-added arterial volume of the photoplethysmographic waveforms during these clinical investigations is limited. In all, 16 normotensive adults (9 men) were recruited to perform 3 provocative test (2 postural changes and 1 resistive breathing) activities with photoplethysmographic signals being monitored on the upper and lower peripheries using customized devices. In all, 4 parameters derived from the photoplethysmographic waveforms that related to the pulsatile tissue blood volume changes were then assessed. The results obtained showed that amplitude-related parameters during these activities showed significant changes (>9.63%; P < .05). However, comparison of pulse-added arterial volume showed insignificant changes (<5.56%; P > .05) for all test settings. Hence, the findings herein suggest that there is clinical potential in using this aspect of the photoplethysmographic waveform.
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Affiliation(s)
- Jong Y A Foo
- Division of Research, Singapore General Hospital and Biomedical & Pharmaceutical Engineering Cluster, Nanyang Technological University, Singapore.
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Zahedi E, Beng GK. Applicability of adaptive noise cancellation to fetal heart rate detection using photoplethysmography. Comput Biol Med 2008; 38:31-41. [PMID: 17706630 DOI: 10.1016/j.compbiomed.2007.06.007] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2006] [Revised: 05/15/2007] [Accepted: 06/25/2007] [Indexed: 11/27/2022]
Abstract
In this paper, an approach based on adaptive noise cancellation (ANC) is evaluated for extraction of the fetal heart rate using photoplethysmographic signals from the maternal abdomen. A simple optical model is proposed in which the maternal and fetal blood pulsations result in emulated signals where the lower SNR limit (fetal to maternal) is -25dB. It is shown that a recursive least-squares algorithm is capable of extracting the peaks of the fetal PPG from these signals, for typical values of maternal and fetal tissues.
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Affiliation(s)
- Edmond Zahedi
- Department of Electrical Engineering, Sharif University of Technology, 11365-9363, Tehran, Iran.
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Mawn T, Nioka S, Nijland M, Bloy L, Elliott MA, Chance B, Leigh JS. Effect of errors in baseline optical properties on accuracy of transabdominal near-infrared spectroscopy in fetal sheep brain during hypoxic stress. JOURNAL OF BIOMEDICAL OPTICS 2005; 10:064001. [PMID: 16409067 DOI: 10.1117/1.2118730] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
A continuous-wave (cw) near-infrared spectroscopy (NIRS) instrument has been developed to noninvasively quantify fetal cerebral blood oxygen saturation (StO2). A linear Green's function formulism was used to analytically solve the photon diffusion equation and extract the time-varying fetal tissue oxy- and deoxy-hemoglobin concentrations from the NIR measurements. Here we explored the accuracy with which this instrument can be expected to perform over a range of fetal hypoxic states. We investigated the dependence of this accuracy on the accuracy of the reference optical properties chosen based on the literature. The fetal oxygenation of a pregnant ewe model was altered via maternal aortic occlusion. The NIR cw instrument was placed on the maternal abdomen directly above the fetal head, continuously acquiring diffuse optical measurements. Blood was sampled periodically from the fetus to obtain fetal arterial saturation (SaO2) measurements from blood gas analysis. The NIR StO2 values were compared with the fetal SaO2 measurements. Variations in the NIR results due to uncertainty in the reference optical properties were relatively small within the fetal SaO2 range of 30 to 80%. Under hypoxic conditions, however, the variability of the NIR StO2 calculations with changes in the assumed reference properties became more significant.
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Affiliation(s)
- Theresa Mawn
- University of Pennsylvania, Department of Bioengineering, Philadelphia, Pennsylvania 19104-6100, USA.
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Jönsson B, Laurent C, Eneling M, Skau T, Lindberg LG. Automatic ankle pressure measurements using PPG in ankle-brachial pressure index determination. Eur J Vasc Endovasc Surg 2005; 30:395-401. [PMID: 15964772 DOI: 10.1016/j.ejvs.2005.05.012] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2004] [Accepted: 05/16/2005] [Indexed: 11/21/2022]
Abstract
OBJECTIVE To evaluate a new technique using a photoplethysmographic (PPG) probe for automatic ankle pressure measurements. DESIGN Comparative study on two techniques for ankle pressure measurement. SETTING University hospital. MATERIAL Thirty-five patients with leg arterial disease and eight healthy volunteers. Ankle-brachial indices (ABPI) were measured using conventional CW Doppler technique and PPG-based prototype equipment for the ankle pressure recordings. CHIEF OUTCOME MEASURES ABPIs calculated from CW Doppler and PPG ankle pressure measurements. The PPG signals were analysed both by visual judgement and by a software based, automatic algorithm. MAIN RESULTS The mean difference between ABPIs calculated from CW Doppler recordings and PPG (visual analysis) was -0.01 (limits of agreement (+/-two standard deviations) +0.16 to -0.19). The correlation coefficient was 0.93. When the algorithm was used, the mean difference (CW Doppler-PPG) was 0.05 (limits of agreement 0.28 to -0.18, r=0.89). CONCLUSIONS The PPG method is a promising technique with an inherent potential for automatisation of the ankle pressure measurements, thereby reducing the observer-dependency in ABPI recordings.
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Affiliation(s)
- B Jönsson
- Department of Cardiovascular Surgery and Anaesthesia, University Hospital, Linköping, Sweden.
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Jönsson B, Laurent C, Skau T, Lindberg LG. A new probe for ankle systolic pressure measurement using photoplethysmography (PPG). Ann Biomed Eng 2005; 33:232-9. [PMID: 15771277 DOI: 10.1007/s10439-005-8982-7] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
An automated method for ankle systolic pressure measurement, less operator dependent than the standard continuous wave (CW) Doppler technique, would imply an advantage both in patient measurements and in epidemiological studies. We present a new photoplethysmographic (PPG) probe that uses near-infrared light (880 nm) to detect pulsatory blood flow underneath the distal end of a standard pneumatic cuff. The probe is adapted to the anatomical conditions at the ankle, permitting recording of pressures in both ankle arteries separately. The validity of the equipment was tested with CW Doppler-derived systolic pressures and invasive blood pressure measurements for reference. In 20 healthy subjects, visual analysis of the PPG curves revealed a mean difference between CW Doppler and PPG measurements of -0.5 mmHg (SD 6.9). Corresponding results for the anterior and posterior tibial arteries separately were -1.8 mmHg (SD 6.2) and 0.9 mmHg (SD 7.3), respectively. A correct probe position was essential for the results. In direct recordings from the dorsalis pedis artery in 10 intensive care patients, PPG underestimated systolic pressure in the anterior tibial artery by 4.5 mmHg (SD 12.1). With further development, the PPG probe, integrated in the pneumatic cuff, may simplify measurements of ankle systolic pressures.
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Affiliation(s)
- B Jönsson
- Department of Cardiovascular Surgery and Anesthesia, University Hospital, Linköping, Sweden.
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Sandberg M, Zhang Q, Styf J, Gerdle B, Lindberg LG. Non-invasive monitoring of muscle blood perfusion by photoplethysmography: evaluation of a new application. ACTA ACUST UNITED AC 2005; 183:335-43. [PMID: 15799770 DOI: 10.1111/j.1365-201x.2005.01412.x] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
AIM To evaluate a specially developed photoplethysmographic (PPG) technique, using green and near-infrared light sources, for simultaneous non-invasive monitoring of skin and muscle perfusion. METHODS Evaluation was based on assessments of changes in blood perfusion to various provocations, such as post-exercise hyperaemia and hyperaemia following the application of liniment. The deep penetrating feature of PPG was investigated by measurement of optical radiation inside the muscle. Simultaneous measurements using ultrasound Doppler and the new PPG application were performed to elucidate differences between the two methods. Specific problems related to the influence of skin temperature on blood flow were highlightened, as well. RESULTS Following static and dynamic contractions an immediate increase in muscle perfusion was shown, without increase in skin perfusion. Liniment application to the skin induced a rapid increase in skin perfusion, but not in muscle. Both similarities and differences in blood flow measured by Ultrasound Doppler and PPG were demonstrated. The radiant power measured inside the muscle, by use of an optical fibre, showed that the near-infrared light penetrates down to the vascular depth inside the muscle. CONCLUSIONS The results of this study indicate the potentiality of the method for non-invasive measurement of local muscle perfusion, although some considerations still have to be accounted for, such as influence of temperature on blood perfusion.
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Affiliation(s)
- M Sandberg
- Department of Rehabilitation Medicine, INR, Faculty of Health Sciences, University Hospital, Linköping, Sweden.
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Laurent C, Jönsson B, Vegfors M, Lindberg LG. Non-invasive measurement of systolic blood pressure on the arm utilising photoplethysmography: development of the methodology. Med Biol Eng Comput 2005; 43:131-5. [PMID: 15742731 DOI: 10.1007/bf02345134] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
Photoplethysmography (PPG) can be used to measure systolic blood pressure at the brachial artery. With a specially designed probe, positioned in the most distal position beneath a pressure cuff on the upper arm, this is possible. The distance between the light source (880 nm) and the photodetector was 20 mm. A test was performed on neuro-intensive care patients by determining blood pressure from the PPG curves, and, when it was compared with systolic blood pressure obtained from inserted indwelling arterial catheters, a correlation factor of r = 0.95 was achieved. The difference between blood pressure obtained using PPG and invasive blood pressure measurement was 3.9 +/- 9.1 mmHg (mean +/- SD), n = 19. The depth to the brachial artery was 13.9 +/- 4.1 mm (mean +/- SD), n = 18. A digital PPG system utilising pulsating light was also developed.
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Affiliation(s)
- C Laurent
- Department of Biomedical Engineering, Linköpings universitet, Sweden.
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Vintzileos AM, Nioka S, Lake M, Li P, Luo Q, Chance B. Transabdominal fetal pulse oximetry with near-infrared spectroscopy. Am J Obstet Gynecol 2005; 192:129-33. [PMID: 15672014 DOI: 10.1016/j.ajog.2004.07.022] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
OBJECTIVE The purpose of this study was to determine the feasibility of noninvasive fetal pulse oximetry in the human fetus with transabdominal continuous-wave near-infrared spectroscopy. STUDY DESIGN The instrument has 3 wavelength light-emitting diodes (735, 805, and 850 nm) as light sources and a photomultiplier tube as a detector. This instrument was used in 6 pregnant women (>36 weeks of gestation). First, a fetal heart rate was obtained with a fetal heart rate monitor. Then, the depth of fetal tissue (head) from the maternal abdomen was determined by ultrasound examination; the distance between the optodes (light source and the detector) was set to be approximately twice the depth of the fetus (7-11 cm). The data analysis was based on the modified Beer-Lambert law and the use of optical densities at 735 and 850 nm to obtain the concentration changes of the oxyhemoglobin and deoxyhemoglobin. The saturation was expressed as the percent of oxygen saturation equal to 100 x oxyhemoglobin/(oxyhemoglobin + deoxyhemoglobin). We recorded the spectroscopy data and the fetal heart rate for approximately 3 to 10 minutes in each patient. RESULTS The mean oxygen saturation values of each of the 6 individual fetuses ranged from 50% to 74% (overall mean saturation, 61% +/- 14.8% [SD]). CONCLUSION This preliminary data indicate that transabdominal fetal pulse oximetry is feasible for human patient application. The measured values were similar to those that are obtained with transvaginal pulse oximetry. Future studies should correlate transabdominally obtained measurements with those measurements that are obtained by transvaginal fetal pulse oximetry.
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Affiliation(s)
- Anthony M Vintzileos
- Department of Obstetrics, Gynecology and Reproductive Sciences, UMDNJ-Robert Wood Johnson Medical School, New Brunswick, NJ, USA
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Abstract
Rapid advances in graphics computing and micro-engineering have offered new techniques for prenatal cardiac imaging. Some of them can be non-invasively applied to both clinical and laboratory settings, including dynamic three-dimensional echocardiography, myocardial Doppler imaging, harmonic ultrasound imaging, and B-flow sonography. With clinical constraints, a few others have been mainly used in laboratories, such as endoscopic ultrasound, magnetic resonance imaging and biomicroscopy. Appropriate use and co-use of these new tools will not only provide unique information for better clinical assessment of fetal cardiac disease but also offer new ways to improved understanding of cardiovascular development and pathogenesis.
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Affiliation(s)
- Jing Deng
- Department of Medical Physics and Bioengineering, University College London, UK.
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