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Silber HA, Gilotra NA, Miller TL. Noninvasive Point of Care Device for Assessing Cardiac Response to Acute Volume Changes. Med Devices (Auckl) 2023; 16:219-227. [PMID: 37908436 PMCID: PMC10614661 DOI: 10.2147/mder.s416845] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2023] [Accepted: 10/04/2023] [Indexed: 11/02/2023] Open
Abstract
Purpose The change in the amplitude of a peripheral pulse in response to a Valsalva maneuver has diagnostic utility for assessing volume status at the bedside. We have developed a device to automatically quantify the Valsalva pulse response (VPR) to a standardized Valsalva maneuver that the device guides a user to perform. In this study, we sought to determine whether VPR by the device, Indicor, is sensitive enough to detect the acute increase in central pressure and volume load that occurs with a passive leg raise (PLR) in healthy volunteers. Methods Healthy volunteers were tested semirecumbently at 45 degrees, then again after being leaned back on a pivoted wedge with legs raised at 45 degrees and torso and head flat, and then again in the semirecumbent position. The device recorded a finger photoplethysmography (PPG) signal during a 10-second expiratory effort of 20 mmHg as guided by the device. VPR was automatically calculated as the ratio of the end-Valsalva pulse amplitude to the baseline pulse amplitude. Results In the 30 participants who completed testing, VPR increased from baseline to PLR in every participant, from 0.34 ± 0.13 to 0.60 ± 0.14 (p < 0.0001). Back upright, VPR decreased back to 0.33 ± 0.10 (p < 0.0001 versus PLR; NS versus baseline position). Conclusion In this proof-of-concept study of healthy participants, the Indicor device, a noninvasive, convenient device that automatically calculates VPR from a finger photoplethysmography signal during a standardized Valsalva maneuver, was sensitive enough to detect the increase in VPR that occurred with an acute central volume load from a PLR. Future studies should examine whether VPR responds differently to a PLR in heart failure patients with abnormal cardiac performance and/or congestion.
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Affiliation(s)
- Harry A Silber
- Department of Medicine, Division of Cardiology, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Nisha A Gilotra
- Department of Medicine, Division of Cardiology, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Thomas L Miller
- Enalare Therapeutics, Inc, Princeton, NJ, USA
- Department of Pediatrics, Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, PA, USA
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Froese L, Sainbhi AS, Gomez A, Marquez I, Amenta F, Batson C, Stein KY, Zeiler FA. Discrete Fourier Transform Windowing Techniques for Cerebral Physiological Research in Neural Injury: A Practical Demonstration. Neurotrauma Rep 2023; 4:410-419. [PMID: 37360544 PMCID: PMC10288301 DOI: 10.1089/neur.2022.0079] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/28/2023] Open
Abstract
To optimally assess oscillatory phenomena within physiological variables, spectral domain transforms are used. A discrete Fourier transform (DFT) is one of the most common methods used to attain this spectral change. In traumatic brain injury (TBI), a DFT is used to derive more complicated methods of physiological assessment, particularly that of cerebrovascular reactivity (CVR). However, a practical application of a DFT will introduce various errors that need to be considered. This study will evaluate the pulse amplitude DFT derivation of intracranial pressure (AMP) to highlight how slight differences in DFT methodologies can impact calculations. Utilizing a high-frequency prospectively maintained data set of TBI patients with recorded arterial and intracranial blood pressure, various cerebral physiological aspects of interest were assessed using the DFT windowing methods of rectangular, Hanning, and Chebyshev. These included AMP, CVR indices (including the pressure reactivity and pulse amplitude index), and the optimal cerebral perfusion pressure (with all methods of CVR). The results of the different DFT-derived windowing methods were compared using the Wilcoxon signed-ranked test and histogram plots between individual patients and over the whole 100-patient cohort. The results for this analysis demonstrate that, overall and for grand average values, there were limited differences between the different DFT windowing techniques. However, there were individual patient outliers to whom the different methods resulted in noticeably different overall values. From this information, for derived indices utilizing a DFT in the assessment of AMP, there are limited differences within the resulting calculations for larger aggregates of data. However, when the amplitude of spectrally resolved response is important and needs to be robust in smaller moments in time, it is recommended to use a window that has amplitude accuracy (such as Chebyshev or flat-top).
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Affiliation(s)
- Logan Froese
- Biomedical Engineering, Rady Faculty of Health Sciences, University of Manitoba, Winnipeg, Manitoba, Canada
| | - Amanjyot Singh Sainbhi
- Biomedical Engineering, Rady Faculty of Health Sciences, University of Manitoba, Winnipeg, Manitoba, Canada
| | - Alwyn Gomez
- Section of Neurosurgery, Department of Surgery, Rady Faculty of Health Sciences, University of Manitoba, Winnipeg, Manitoba, Canada
- Department of Human Anatomy and Cell Science, Rady Faculty of Health Sciences, University of Manitoba, Winnipeg, Manitoba, Canada
| | - Izzy Marquez
- Undergraduate Engineering Program, Department of Biosystems Engineering, Price Faculty of Engineering, Rady Faculty of Health Sciences, University of Manitoba, Winnipeg, Manitoba, Canada
| | - Fiorella Amenta
- Undergraduate Engineering Program, Department of Biosystems Engineering, Price Faculty of Engineering, Rady Faculty of Health Sciences, University of Manitoba, Winnipeg, Manitoba, Canada
| | - Carleen Batson
- Department of Human Anatomy and Cell Science, Rady Faculty of Health Sciences, University of Manitoba, Winnipeg, Manitoba, Canada
| | - Kevin Y. Stein
- Biomedical Engineering, Rady Faculty of Health Sciences, University of Manitoba, Winnipeg, Manitoba, Canada
| | - Frederick A. Zeiler
- Biomedical Engineering, Rady Faculty of Health Sciences, University of Manitoba, Winnipeg, Manitoba, Canada
- Section of Neurosurgery, Department of Surgery, Rady Faculty of Health Sciences, University of Manitoba, Winnipeg, Manitoba, Canada
- Department of Human Anatomy and Cell Science, Rady Faculty of Health Sciences, University of Manitoba, Winnipeg, Manitoba, Canada
- Department of Clinical Neuroscience, Karolinska Institutet, Stockholm, Sweden
- Division of Anaesthesia, Department of Medicine, Addenbrooke's Hospital, University of Cambridge, Cambridge, United Kingdom
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Wang J, Bi J, Xu Y, Niu G, Liu M, Stempitsky V. Effects of Charge Trapping on Memory Characteristics for HfO 2-Based Ferroelectric Field Effect Transistors. Nanomaterials (Basel) 2023; 13:638. [PMID: 36839006 PMCID: PMC9959327 DOI: 10.3390/nano13040638] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/31/2022] [Revised: 01/24/2023] [Accepted: 01/30/2023] [Indexed: 06/18/2023]
Abstract
A full understanding of the impact of charge trapping on the memory window (MW) of HfO2-based ferroelectric field effect transistors (FeFETs) will permit the design of program and erase protocols, which will guide the application of these devices and maximize their useful life. The effects of charge trapping have been studied by changing the parameters of the applied program and erase pulses in a test sequence. With increasing the pulse amplitude and pulse width, the MW increases first and then decreases, a result attributed to the competition between charge trapping (CT) and ferroelectric switching (FS). This interaction between CT and FS is analyzed in detail using a single-pulse technique. In addition, the experimental data show that the conductance modulation characteristics are affected by the CT in the analog synaptic behavior of the FeFET. Finally, a theoretical investigation is performed in Sentaurus TCAD, providing a plausible explanation of the CT effect on the memory characteristics of the FeFET. This work is helpful to the study of the endurance fatigue process caused by the CT effect and to optimizing the analog synaptic behavior of the FeFET.
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Affiliation(s)
- Jianjian Wang
- Institute of Microelectronics, Chinese Academy of Sciences, Beijing 100029, China
- School of Microelectronics, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Jinshun Bi
- Institute of Microelectronics, Chinese Academy of Sciences, Beijing 100029, China
- School of Microelectronics, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Yannan Xu
- Institute of Microelectronics, Chinese Academy of Sciences, Beijing 100029, China
| | - Gang Niu
- School of Electronic Science, Xi’an Jiaotong University, Xi’an 710049, China
| | - Mengxin Liu
- Institute of Microelectronics, Chinese Academy of Sciences, Beijing 100029, China
- School of Microelectronics, University of Chinese Academy of Sciences, Beijing 100049, China
- Beijing Zhongke New Micro Technology Department Co., Ltd., Beijing 100029, China
| | - Viktor Stempitsky
- Department of Microelectronics, Belarusian State University of Informatics and Radioelectronics, 220015 Minsk, Belarus
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Saito M, Jingu H, Osawa H, Oyama Y, Tanaka T, Shiono A, Machida M. Pulse Amplitude Measured with a Portable Laser Doppler Flowmeter Is Useful for Screening of Dialysis Patients for Peripheral Arterial Disease: An Observational Study. Ann Vasc Dis 2022; 15:301-307. [PMID: 36644273 PMCID: PMC9816036 DOI: 10.3400/avd.oa.21-00126] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2021] [Accepted: 10/08/2022] [Indexed: 11/27/2022] Open
Abstract
Objective: The objective of this study was to use a portable laser Doppler flowmeter (LDF) to measure the toe blood flow and pulse amplitude as a screening test for peripheral arterial disease (PAD) in dialysis patients and compare the diagnostic abilities of the aforementioned parameters measured using an LDF with those of the ankle-brachial index (ABI) and toe brachial index (TBI). Methods: The 14 patients in this retrospective study received maintenance hemodialysis (HD). We measured the blood flow and pulse amplitude on the ventral side of the first toe with a portable LDF while the patients were undergoing an HD session. The correlations between the blood flow/pulse amplitude in the toe and the ABI/TBI were examined. Results: Both the ABI and TBI had a strong correlation with pulse amplitude. The sensitivity and specificity of the pulse amplitude measured with the LDF for detecting PAD in HD patients as determined by a receiver operating characteristic curve analysis were 1.00 and 0.88, respectively. Conclusion: Measuring the pulse amplitude in the toe with a portable LDF may serve as a simple and useful screening test for PAD in HD patients.
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Affiliation(s)
- Makoto Saito
- Department of Clinical Engineering, Public Tomioka General Hospital, Tomioka, Gunma, Japan,Corresponding author: Makoto Saito, AS. Department of Clinical Engineering, Public Tomioka General Hospital, 2073-1 Tomioka, Tomioka, Gunma 370-2393, Japan Tel: +81-274-63-2111, Fax: +81-274-64-3377, E-mail:
| | - Hiroomi Jingu
- Department of Clinical Engineering, Public Tomioka General Hospital, Tomioka, Gunma, Japan
| | - Hidefumi Osawa
- Department of Urology, Public Tomioka General Hospital, Tomioka, Gunma, Japan
| | - Yusuke Oyama
- Department of Urology, Public Tomioka General Hospital, Tomioka, Gunma, Japan
| | - Toshiyuki Tanaka
- Department of Urology, Public Tomioka General Hospital, Tomioka, Gunma, Japan
| | - Akihiko Shiono
- Department of Urology, Public Tomioka General Hospital, Tomioka, Gunma, Japan
| | - Masami Machida
- Department of Urology, Public Tomioka General Hospital, Tomioka, Gunma, Japan
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Uryga A, Ziółkowski A, Kazimierska A, Pudełko A, Mataczyński C, Lang EW, Czosnyka M, Kasprowicz M, Anke A, Beer R, Bellander BM, Beqiri E, Buki A, Cabeleira M, Carbonara M, Chieregato A, Citerio G, Clusmann H, Czeiter E, Czosnyka M, Depreitere B, Ercole A, Frisvold S, Helbok R, Jankowski S, Kondziella D, Koskinen LO, Kowark A, Menon DK, Meyfroidt G, Moeller K, Nelson D, Piippo-Karjalainen A, Radoi A, Ragauskas A, Raj R, Rhodes J, Rocka S, Rossaint R, Sahuquillo J, Sakowitz O, Smielewski P, Stocchetti N, Sundström N, Takala R, Tamosuitis T, Tenovuo O, Unterberg A, Vajkoczy P, Vargiolu A, Vilcinis R, Wolf S, Younsi A, Zeiler FA. Analysis of intracranial pressure pulse waveform in traumatic brain injury patients: a CENTER-TBI study. J Neurosurg 2022:1-11. [PMID: 36681948 DOI: 10.3171/2022.10.jns221523] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2022] [Accepted: 10/28/2022] [Indexed: 12/24/2022]
Abstract
OBJECTIVE Intracranial pressure (ICP) pulse waveform analysis may provide valuable information about cerebrospinal pressure-volume compensation in patients with traumatic brain injury (TBI). The authors applied spectral methods to analyze ICP waveforms in terms of the pulse amplitude of ICP (AMP), high frequency centroid (HFC), and higher harmonics centroid (HHC) and also used a morphological classification approach to assess changes in the shape of ICP pulse waveforms using the pulse shape index (PSI). METHODS The authors included 184 patients from the Collaborative European NeuroTrauma Effectiveness Research in Traumatic Brain Injury (CENTER-TBI) High-Resolution Sub-Study in the analysis. HFC was calculated as the average power-weighted frequency within the 4- to 15-Hz frequency range of the ICP power density spectrum. HHC was defined as the center of mass of the ICP pulse waveform harmonics from the 2nd to the 10th. PSI was defined as the weighted sum of artificial intelligence-based ICP pulse class numbers from 1 (normal pulse waveform) to 4 (pathological waveform). RESULTS AMP and PSI increased linearly with mean ICP. HFC increased proportionally to ICP until the upper breakpoint (average ICP of 31 mm Hg), whereas HHC slightly increased with ICP and then decreased significantly when ICP exceeded 25 mm Hg. AMP (p < 0.001), HFC (p = 0.003), and PSI (p < 0.001) were significantly greater in patients who died than in patients who survived. Among those patients with low ICP (< 15 mm Hg), AMP, PSI, and HFC were greater in those with poor outcome than in those with good outcome (all p < 0.001). CONCLUSIONS Whereas HFC, AMP, and PSI could be used as predictors of mortality, HHC may potentially serve as an early warning sign of intracranial hypertension. Elevated HFC, AMP, and PSI were associated with poor outcome in TBI patients with low ICP.
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Affiliation(s)
- Agnieszka Uryga
- 1Department of Biomedical Engineering, Faculty of Fundamental Problems of Technology, Wroclaw University of Science and Technology, Wroclaw, Poland
| | - Arkadiusz Ziółkowski
- 1Department of Biomedical Engineering, Faculty of Fundamental Problems of Technology, Wroclaw University of Science and Technology, Wroclaw, Poland
| | - Agnieszka Kazimierska
- 1Department of Biomedical Engineering, Faculty of Fundamental Problems of Technology, Wroclaw University of Science and Technology, Wroclaw, Poland
| | - Agata Pudełko
- 1Department of Biomedical Engineering, Faculty of Fundamental Problems of Technology, Wroclaw University of Science and Technology, Wroclaw, Poland
| | - Cyprian Mataczyński
- 2Department of Computer Engineering, Faculty of Information and Communication Technology, Wroclaw University of Science and Technology, Wroclaw, Poland
| | - Erhard W Lang
- 3Neurosurgical Associates, Red Cross Hospital, Kassel, Germany.,4Department of Neurosurgery, Faculty of Medicine, Georg-August-Universität, Göttingen, Germany
| | - Marek Czosnyka
- 5Brain Physics Laboratory, Department of Clinical Neurosciences, Division of Neurosurgery, Addenbrooke's Hospital, University of Cambridge, Cambridge, United Kingdom; and.,6Institute of Electronic Systems, Faculty of Electronics and Information Technology, Warsaw University of Technology, Warsaw, Poland
| | - Magdalena Kasprowicz
- 1Department of Biomedical Engineering, Faculty of Fundamental Problems of Technology, Wroclaw University of Science and Technology, Wroclaw, Poland
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D'Antona L, Craven CL, Bremner F, Matharu MS, Thorne L, Watkins LD, Toma AK. Effect of position on intracranial pressure and compliance: a cross-sectional study including 101 patients. J Neurosurg 2021:1-9. [PMID: 34715658 DOI: 10.3171/2021.6.jns203573] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2020] [Accepted: 06/03/2021] [Indexed: 11/06/2022]
Abstract
OBJECTIVE A better understanding of the effect of position on intracranial pressure (ICP) and compliance is important for the development of treatment strategies that can restore normal cerebrospinal fluid (CSF) dynamics. There is limited knowledge on the effect of position on intracranial compliance. In this cross-sectional study the authors tested the association of pulse amplitude (PA) with position and the day/night cycle. Additionally, they describe the postural ICP and PA changes of patients with "normal" ICP dynamics. METHODS This single-center retrospective study included patients with suspected and/or confirmed CSF dynamics abnormalities who had been examined with elective 24-hour ICP monitoring between October 2017 and September 2019. Patients had been enrolled in a short exercise battery including four positions: supine, lumbar puncture position in the left lateral decubitus position, sitting, and standing. Each position was maintained for 2 minutes, and mean ICP and PA were calculated for each position. The 24-hour day and night median ICP and PA data were also collected. Linear regression models were used to test the correlation of PA with position and day/night cycle. All linear regressions were corrected for confounders. The postural ICP monitoring results of patients without obvious ICP dynamics abnormality were summarized. RESULTS One hundred one patients (24 males and 77 females) with a mean age of 39 ± 13years (mean ± standard deviation) were included in the study. The adjusted linear regression models demonstrated a significant association of ICP with position and day/night cycle, with upright (sitting and standing) and day ICP values lower than supine and night ICP values. The adjusted linear regression model was also significant for the association of PA with position and day/night cycle, with upright and day PA values higher than supine and night PA results. These associations were confirmed for patients with and without shunts. Patients without clear ICP dynamics abnormality had tighter control of their postural ICP changes than the other patients; however, the difference among groups was not statistically significant. CONCLUSIONS This is the largest study investigating the effect of postural changes on intracranial compliance. The results of this study suggest that PA, as well as ICP, is significantly associated with posture, increasing in upright positions compared to that while supine. Further studies will be needed to investigate the mechanism behind this association.
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Affiliation(s)
- Linda D'Antona
- 1Victor Horsley Department of Neurosurgery, The National Hospital for Neurology and Neurosurgery, Queen Square.,2UCL Queen Square Institute of Neurology
| | - Claudia Louise Craven
- 1Victor Horsley Department of Neurosurgery, The National Hospital for Neurology and Neurosurgery, Queen Square
| | - Fion Bremner
- 2UCL Queen Square Institute of Neurology.,3Department of Neuro-Ophthalmology, The National Hospital for Neurology and Neurosurgery; and
| | - Manjit Singh Matharu
- 4Headache and Facial Pain Group, The National Hospital for Neurology and Neurosurgery, London, United Kingdom
| | - Lewis Thorne
- 1Victor Horsley Department of Neurosurgery, The National Hospital for Neurology and Neurosurgery, Queen Square
| | - Laurence Dale Watkins
- 1Victor Horsley Department of Neurosurgery, The National Hospital for Neurology and Neurosurgery, Queen Square
| | - Ahmed Kassem Toma
- 1Victor Horsley Department of Neurosurgery, The National Hospital for Neurology and Neurosurgery, Queen Square.,2UCL Queen Square Institute of Neurology
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Abbott CC, Quinn D, Miller J, Ye E, Iqbal S, Lloyd M, Jones TR, Upston J, De Deng Z, Erhardt E, McClintock SM. Electroconvulsive Therapy Pulse Amplitude and Clinical Outcomes. Am J Geriatr Psychiatry 2021; 29:166-178. [PMID: 32651051 PMCID: PMC7744398 DOI: 10.1016/j.jagp.2020.06.008] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/08/2019] [Revised: 06/09/2020] [Accepted: 06/10/2020] [Indexed: 10/24/2022]
Abstract
INTRODUCTION Electroconvulsive therapy (ECT) pulse amplitude, which determines the induced electric field magnitude in the brain, is currently set at 800-900 milliamperes (mA) on modern ECT devices without any clinical or scientific rationale. The present study assessed differences in depression and cognitive outcomes for three different pulse amplitudes during an acute ECT series. We hypothesized that the lower amplitudes would maintain the antidepressant efficacy of the standard treatment and reduce the risk of neurocognitive impairment. METHODS This double-blind investigation randomized subjects to three treatment arms: 600, 700, and 800 mA (active comparator). Clinical, cognitive, and imaging assessments were conducted pre-, mid- and post-ECT. Subjects had a diagnosis of major depressive disorder, age range between 50 and 80 years, and met clinical indication for ECT. RESULTS The 700 and 800 mA arms had improvement in depression outcomes relative to the 600 mA arm. The amplitude groups showed no differences in the primary cognitive outcome variable, the Hopkins Verbal Learning Test-Revised (HVLT-R) retention raw score. However, secondary cognitive outcomes such as the Delis Kaplan Executive Function System Letter and Category Fluency measures demonstrated cognitive impairment in the 800 mA arm. DISCUSSION The results demonstrated a dissociation of depression (higher amplitudes better) and cognitive (lower amplitudes better) related outcomes. Future work is warranted to elucidate the relationship between amplitude, electric field, neuroplasticity, and clinical outcomes.
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Affiliation(s)
- Christopher C Abbott
- Department of Psychiatry (CCA, DQ, JM, EY, SI, ML, TRJ, JU), University of New Mexico, Albuquerque, NM.
| | - Davin Quinn
- Department of Psychiatry, University of New Mexico, Albuquerque, NM
| | - Jeremy Miller
- Department of Psychiatry, University of New Mexico, Albuquerque, NM
| | - Enstin Ye
- Department of Psychiatry, University of New Mexico, Albuquerque, NM
| | - Sulaiman Iqbal
- Department of Psychiatry, University of New Mexico, Albuquerque, NM
| | - Megan Lloyd
- Department of Psychiatry, University of New Mexico, Albuquerque, NM
| | - Thomas R Jones
- Department of Psychiatry, University of New Mexico, Albuquerque, NM
| | - Joel Upston
- Department of Psychiatry, University of New Mexico, Albuquerque, NM
| | - Zhi De Deng
- Noninvasive Neuromodulation Unit, Experimental Therapeutics and Pathophysiology Branch, National Institute of Mental Health, National Institutes of Health, Bethesda, MD,Division of Brain Stimulation and Neurophysiology, Department of Psychiatry and Behavioral Sciences, Duke University School of Medicine, Durham, NC
| | - Erik Erhardt
- Department of Mathematics and Statistics, University of New Mexico, Albuquerque, NM
| | - Shawn M McClintock
- Division of Psychology, Department of Psychiatry, UT Southwestern Medical Center, Dallas, TX,Division of Brain Stimulation and Neurophysiology, Department of Psychiatry and Behavioral Sciences, Duke University School of Medicine, Durham, NC
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Abstract
Arterial volume clamping uses external compression of an artery to provide continuous non-invasive measurement of arterial blood pressure. It has been assumed that mean arterial pressure (MAP) corresponds to the point where unloading leads to the maximum oscillation of the arterial wall as reflected by photoplethysmogram (PPG), an assumption that has been challenged. Five subjects were recruited for the study (three males, mean age (SD) = 32 (15) years). The PPG waveform was analysed to identify the relationship between the external compressing pressure, PPG pulse amplitude and MAP. Two separate tests were carried out at compression step intervals of 10 mmHg and 2 mmHg, respectively. No significant differences were found between the two tests. The bias between the compressing pressure and the MAP was -4.7 ± 5.63 mmHg (p < 0.001) showing a normal distribution. Further research is needed to identify optimal algorithms for estimation of MAP using PPG associated with arterial compression.
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Affiliation(s)
- K Y Chin
- Department of Medical Physics, University Hospitals of Leicester NHS Trust, Leicester Royal Infirmary , Leicester LE1 5WW , UK
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Abstract
Pacing leads without the elution of dexamethasone from the electrode tip usually have an unpredictable increase of pacing threshold within the first few months after implantation. During follow-up, pacing thresholds remained significantly above the level at the time of implantation. The specific clinical effect of local steroid elution is to attenuate the increase of pacing threshold during lead maturation and to maintain low pacing thresholds during follow-up. With pacing thresholds less than 2.5V at 0.5ms pulse duration in more than 95%, patients with steroid-eluting leads rarely have a significant pacing threshold increase compared to patients with non-steroid leads. Steroid elution made the implantation of pacing leads with a small surface of 1.2mm(2) feasible. An advantage of these leads is a higher pacing impedance with values above 1000 ohms, in addition to constant pacing thresholds, which additionally reduces the pacing current. Steroid-elution also avoids in screw-in leads the postoperative threshold peaking, and long-term pacing thresholds were lower compared to non-steroid controls. The local steroid elution itself has no effect on pacing impedance or P/R-wave sensing.
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Affiliation(s)
- A Schuchert
- Medical Clinic Department of Cardiology University-Hospital Hamburg-Eppendorf Martinistr. 52 20246 Hamburg, Germany Tel.: +49-4042803-5304 Fax: +49-4042803-5677 E-Mail: , Germany
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