Hallux pressure measurement device

Abstract

Obliterating arteriosclerosis is currently a major public health problem. In association with other conditions and due directly by them, like diabetes, hyperlipidemia, smoking habit, hypertension and renal diseases, leads to arterial occlusions, well known in the cardiologic area by coronary disease, and in the extremities by lower limb ischemia, that in its most severe manifestation results in thousands of major amputations annually. One of the critical aspects in the management of these extremities with threatening ischemia is the estimation and quantification of the degree of ischemia, factor determination the choice of treatment. Facing the situation of absence of palpable pulse over arterial paths and knowing that part of distal perfusion is provided by secondary arteries, measurement of oxygen supply is proposed by distinct manners, that are under constant research and evaluation. The most used is the measurement of arterial pressure with cuffs applied at ankle level compared with arm pressure, and relation between those known as ankle/brachial index (ABI). Obvious limitation of this method is that the pathological process involves hardening of the arteries (arteriosclerosis), and frequently main arteries in the region of lower leg and ankle are not compressible by the cuff, especially when severe calcification occurs in diabetes and renal disease, making measures impossible or imprecise. Pressure measurement at the hallux or other toes is the proposed alternative to estimation of ischemia level, mostly using photoplethysmography and special cuffs. Although this method is universally accepted and the most used, limitations should be considered due to the fact they are based on the principle of pulse oximetry, as devices usually employed in ICU, and for the specific purpose of lower limb ischemia measurement considered as having low sensitivity and sensibility (1). Also, devices especially constructed for the purpose of distal perfusion measurements are not available in our market, and have a high cost, what limit use among us. Another method described for pressure measurement uses the oscillometric principle, and to time is not referred for toe gauging. Objective of present project is the development of a device for measurement of arterial pressure at the hallux based in a photoplethysmography sensor (PPGMAX30100) and display (Oled 0,96'', 128x64) coupled to a microcontroller Arduino, and compare results measured with device constructed based on the same principle by Atys Sys Toe (Atys Medical, UK). Results will also be compared to measurements obtained by sensor AMS 5915 (Analog Microelectronics), that uses the oscillometric principle. (AU)