Transducer system for the noninvasive recording of arterial pressure contours

Abstract

A transducer system is described that permits noninvasive recordings of the pressure-vs-time arterial profile at any palpable site on the body. A thin (30 microns) piezoelectric polymer film of polyvinylidene fluoride serves as the active element and as the mechanical coupler to the skin. The system has high frequency response and a low frequency cut-off of 0.16 Hz. The active element and its support provides a good mechanical impedance match with the skin. The transducer housing resembles a thick wrist watch and is strapped in place. The complete system is designed to record as many as four simultaneous profiles on a subject. Comparisons of the noninvasive transducer records with records taken with an indwelling catheter indicate congruence of the two signals and the first and second derivatives of the two signals, both when the transducer is applied directly to the skin and when a layer of fat is interposed between the skin and the transducer. The system provides a simple atraumatic means of periodically screening and/or monitoring cardiovascular changes in large populations of subjects and would provide a means of tracking changes induced by therapeutic programs.

Noninvasive method for determining blood pressure and contours of arterial and volume pulses

“…As Chio [13] has explained, if P>sbp, the arterial vessels in the arm are blocked and function as a vibration-conducting medium; the pulse contour found through suprasystolic cuff sphygmography are therefore expected to represent the arterial pulse itself; a comparison of some typical contours, plotted in Figure 7, with the waveforms published by previous investigators [23,24] fully supports this surmise. It should be noted that, since the values of sbp and dbp have already been determined, the vertical scale can be immediately converted to the blood pressure itself.…”

“…In the past, contours of the brachial pulse have been obtained either directly, through brachial arterial puncture [23], or indirectly, by applying a piezoelectric sensor directly over the artery [24]; the latter arrangement is incapable of reading absolute pressure. It is a matter of considerable interest to ask whether sphygmopiezophonometry alone can provide the contour of the brachial pulse.…”

Influence of Contact Forces on Wrist Photo plethysmography – Prestudy for a Wearable Patient Monitor / Einfluß von Kontaktkräften auf die photoplethysmografische Pulsmessung am Handgelenk – Vorstudie zu einem tragbaren Patientenmonitor

“…Blood pressure-induced surface deflections are detected with mechanical devic-es; therefore pressure gauges or force sensitive materials like PVD [2] are typically used. Both mechanical and optical devices are in use for the detection of arterial pulses on the skin surface.…”

Validation of a Polyvinylidene Fluoride Impedance Sensor for Respiratory Event Classification during Polysomnography

“…PVDF is a specialty fluoropolymer substance which reacts almost instantaneously to changes in temperature, pressure, strain, and impedance, making it a potentially useful substrate to sense respiratory flow or effort. [9][10][11] Similar to inductance plethysmography, PVDF can be incorporated into a belt surrounding the chest and abdomen but unlike RIP, PVDF measures impedance and not inductance to estimate breathing and respiratory effort. Use of inductance technologies for respiratory measurement is based on the principle that the changes in current in the coiled wires surrounding the chest or abdomen induced by breathing are linearly proportional to changes in the cross-sectional areas occurring during breathing.…”