Electrical admittance cuff for noninvasive and simultaneous measurement of haematocrit, arterial pressure and elasticity using volume-oscillometric method

Dual frequency bioelectrical impedance analysis to estimate hematocrit for prognosis of dengue fever in Indian children

A noninvasive investigation to ascertain the hematocrit (HCT) or packed cell volume (PCV) was conducted on 44 hospitalized dengue hemorrhagic fever (DHF) subjects, male and female aged between 3 and 14 years using bioelectrical impedance analysis (BIA). Among the 44 subjects, 30 subjects were confirmed to be non-structural protein-1 (NS1) positive at the time of admission, whose blood investigations such as HCT level, platelet (PLT) count, aspartate aminotransferase (AST) level and alanine aminotransferase (ALT) level were taken for the classification of risk as low risk (LR) and high risk (HR) DHF. Electrical conductivity of blood reflects a linear correlation with HCT. To provide a better and more accurate estimate of HCT, a dual frequency method is proposed to calculate the conductivities of plasma and blood cells. The resistance at 100 kHz is used to estimate the conductivity of blood cells and the impedance at 5 kHz to estimate the conductivity of plasma. Statistical analysis reveals that the HCT estimated using the proposed dual frequency method shows a significant difference with a single frequency (50 kHz) estimate of HCT and also shows a good correlation with the blood investigation results. In addition, statistical analysis of the proposed method on different fever subjects indicates a significant difference with DHF.

Noninvasive imaging of flowing blood cells using label-free spectrally encoded flow cytometry

Optical microscopy of blood cells in vivo provides a unique opportunity for clinicians and researchers to visualize the morphology and dynamics of circulating cells, but is usually limited by the imaging speed and by the need for exogenous labeling of the cells. Here we present a label-free approach for in vivo flow cytometry of blood using a compact imaging probe that could be adapted for bedside real-time imaging of patients in clinical settings, and demonstrate subcellular resolution imaging of red and white blood cells flowing in the oral mucosa of a human volunteer. By analyzing the large data sets obtained by the system, valuable blood parameters could be extracted and used for direct, reliable assessment of patient physiology.

Point-of-care noninvasive hemoglobin determination using fiber optic reflectance spectroscopy

STUDY OBJECTIVE

Rapidly identifying anemia through qualitative observation of the palpebral conjunctiva for pallor is standard medical practice. We report on the ability of using a fiber optic array probe to collect diffusely reflected light from the palpebral conjunctiva and measure hemoglobin concentration noninvasively. Patients (N=102) admitted to the emergency department and receiving a complete blood count (CBC) were enrolled as a convenience set. The tarsal plate was exposed by averting the lower eyelid and illuminated with a white LED while diffusely reflected light was collected using a fiber optic probe and commercial grating spectrometer. Spectra were analyzed using partial least squares regression to extract hemoglobin concentration information and compare to the CBC result. The probe and algorithm demonstrated correlation coefficient of r = 0.82 and standard error of 1.05 g/dL compared to invasive CBC test. Experimental error is due to variability in distance and position of the probe relative to the conjunctiva. This technique has shown the ability to measure total hemoglobin noninvasively and in real-time at the point-of-care using diffuse reflectance spectroscopy of the tarsal plate, leading to potential inclusion of this class of device as a triage centric tool to identify anemia appearing with internal hemorrhage or other acute conditions.

Noninvasive Optical, Electrical, and Acoustic Methods of Total Hemoglobin Determination

Background: Anemia is an underdiagnosed, significant public health concern afflicting >2 billion people worldwide. The detrimental effects of tissue oxygen deficiency on the cardiovascular system and concurrent appearance of anemia with numerous high-risk disorders highlight the importance of clinical screening. Currently there is no universally accepted, clinically applicable, noninvasive hemoglobin/hematocrit screening tool. The need for such a device has prompted an investigation into a breadth of techniques.

Methods: A synopsis of the literature and current directions of research in noninvasive total hemoglobin measurement was collected. Contributions highlighted in this review are limited to those studies conducted with a clinical aspect, and most include in vivo patient studies.

Results: The review of potential techniques presented here includes optoacoustic spectroscopy, spectrophotometric imaging, diffuse reflectance spectroscopy, transcutaneous illumination, electrical admittance plethysmography, and photoplethysmography. The technological performance, relative benefits of each approach, potential instrumentation design considerations, and future directions are discussed in each subcategory.

Conclusions: Many techniques reviewed here have shown excellent accuracy, sensitivity, and specificity in measuring hemoglobin/hematocrit, thus in the near future a new clinically viable tool for noninvasive hemoglobin/hematocrit monitoring will likely be widely used for patient care. Limiting factors in clinical adoption will likely involve technology integration into the current standard of care in each field routinely dealing with anemia.

Non-invasive Monitoring of Hemodynamic Changes During Hemodialysis by the Use of a Newly Developed Admittance Cardiograph

Only a little information is available for the evaluation of the complex hemodynamic changes that occur during hemodialysis. Recently, we developed the transthoracic electrical admittance cardiograph for repeated measurements of cardiac output, and monitored hemodynamic changes during hemodialysis by the use of this device. We measured cardiovascular hemodynamic and autonomic parameters non-invasively during 210 min of hemodialysis in 19 chronic hemodialysis patients who for more than 2 months had no history of cardiovascular collapses during hemodialysis. Blood pressure was monitored every 10 min using a cuff-oscillometric device (TM-2425; A & D, Tokyo, Japan). Cardiac output was monitored on a beat-by-beat basis by a newly developed electrical admittance cardiograph (NICOVIEW PA1100; NEC, Tokyo, Japan). Electrocardiogram R-R intervals were also monitored by the TM-2425. Power spectral analysis of R-R intervals was performed to obtain the low-frequency (LF; 0.05-0.15 Hz) and the high-frequency (HF; 0.15-0.40 Hz) components based on an autoregressive model. Change in circulatory blood volume was also monitored by a CRIT-LINE (In-Line Diagnostics, Riverdale, UT, USA). Although blood volume declined significantly by 16.3 +/- 1.4% (mean +/- SE) during hemodialysis (P < 0.0001), mean blood pressure did not change significantly. Heart rate increased significantly from the initial values of 76.3 +/- 3.4-86.4 +/- 4.9 beats/min (P = 0.03). Cardiac output and stroke volume decreased significantly from 4.47 +/- 0.30 to 2.91 +/- 0.32 L/min (P < 0.0001), and from 57.0 +/- 3.7 to 33.9 +/- 3.1 mL (P < 0.0001), respectively. Total peripheral vascular resistance increased significantly from 1940 +/- 146 to 3117 +/- 280 dyne x s x cm(5) (P < 0.0001). The LF component did not show significant change, while the HF component decreased significantly (P = 0.007), and the LF/HF ratio increased significantly (P = 0.03). These results suggest that a reduction in parasympathetic nerve activity and sympathetic nerve activation and a marked increase in total peripheral vascular resistance are responsible for the maintenance of blood pressure during hemodialysis in chronic hemodialysis patients. The admittance cardiograph seems to be one of the best options for serial measurements of cardiac output.