Yu Imachi

Development of optoelectronic monitoring system for ear arterial pressure waveforms

Invasive intra-arterial blood pressure measurement is the most accurate method but not practical if the subject is in motion. The apparatus developed by Wesseling et al., based on a volume-clamp method of Penaz (Finapres), is able to monitor continuous finger arterial pressure waveforms noninvasively. The limitation of Finapres is the difficulty in measuring the pressure of a subject during work that involves finger or arm action. Because the Finapres detector is attached to subjects finger, the measurements are affected by inertia of blood and hydrostatic effect cause by arm or finger motion. To overcome this problem, the authors made a detector that is attached to subjects ear and developed and optoelectronic monitoring systems for ear arterial pressure waveform (Earpres). An IR LEDs, photodiode, and air cuff comprised the detector. The detector was attached to a subjects ear, and the space adjusted between the air cuff and the rubber plate on which the LED and photodiode were positioned. To evaluate the accuracy of Earpres, the following tests were conducted with participation of 10 healthy male volunteers. The subjects rested for about five minutes, then performed standing and squatting exercises to provide wide ranges of systolic and diastolic arterial pressure. Intra- and inter-individual standard errors were calculated according to the method of van Egmond et al. As a result, average, the averages of intra-individual standard errors for earpres appeared small (3.7 and 2.7 mmHg for systolic and diastolic pressure respectively). The inter-individual standard errors for Earpres were about the same was Finapres for both systolic and diastolic pressure. The results showed the ear monitor was reliable in measuring arterial blood pressure waveforms and might be applicable to various fields such as sports medicine and ergonomics.

Validation of optoelectronic monitoring system for ear arterial pressure waveforms in practical use

A newly developed optoelectronic monitoring systems for ear arterial pressure waveform (Earpres) was tested in ergonomics and sports science. Changes in systolic and diastolic blood pressures and heart rate were continuously measured by the system during VDT operations such as word processing and computer games, and during two different styles of weight lifting, one-hand and two-hands curls, with three different weights respectively. Statistical analysis of the results showed that systolic and diastolic blood pressures and heart rate increased during VDT operation, and in the extreme case the increments of those were as high as 78 mmHg and 50mmHg respectively during computer game operation and 50 bpm during word processor operation. It was also statistically clarified that systolic and diastolic blood pressures and heart rate increased in accordance with weight during one-hand and two-hands curls. It was ascertained that the results obtained by Earpres agreed for the most part with physiological knowledge; some results might be new findings. Earpres was thus validated as a physiologically and ergonomically useful apparatus. Additionally, an apparatus was constructed to detect the exact location of an artery in the ear, composed of a halogen lamp, a band-pass filter, a bundle of optical fibers, and a CCD device. With the apparatus, Earpres became much easier to handle.