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Sensors 2012, 12(2), 1816-1826; doi:10.3390/s120201816

Evaluation of Electrical and Optical Plethysmography Sensors for Noninvasive Monitoring of Hemoglobin Concentration

* ,
School of Engineering and Mathematical Sciences, City University London, Northampton Square, London EC1V 0HB, UK
* Author to whom correspondence should be addressed.
Received: 14 December 2011 / Revised: 31 January 2012 / Accepted: 3 February 2012 / Published: 9 February 2012
(This article belongs to the Special Issue Optical Sensors in Medicine)
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Completely noninvasive monitoring of hemoglobin concentration has not yet been fully realized in the clinical setting. This study investigates the viability of measuring hemoglobin concentration noninvasively by evaluating the performance of two types of sensor using a tissue phantom perfused with a blood substitute. An electrical sensor designed to measure blood volume changes during the cardiac cycle was used together with an infrared optical sensor for detection of erythrocyte-bound hemoglobin. Both sensors demonstrated sensitivity to changes in pulse volume (plethysmography). The electrical sensor produced a signal referred to as capacitance plethysmograph (CPG) a quantity which was invariant to the concentration of an infrared absorbing dye present in the blood substitute. The optical sensor signal (photoplethysmograph) increased in amplitude with increasing absorber concentration. The ratio PPG:CPG is invariant to pulse pressure. This quantity is discussed as a possible index of in vivo hemoglobin concentration.
Keywords: hemoglobin; capacitance; plethysmography; noninvasive hemoglobin; capacitance; plethysmography; noninvasive
This is an open access article distributed under the Creative Commons Attribution License (CC BY) which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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Phillips, J.P.; Hickey, M.; Kyriacou, P.A. Evaluation of Electrical and Optical Plethysmography Sensors for Noninvasive Monitoring of Hemoglobin Concentration. Sensors 2012, 12, 1816-1826.

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