Pulse Transit Time Measurement Using Bioimpedance

Abstract

Cardiovascular disease is a factor that leads to mortality in the populations of industrialized countries, being the large arteries pathology the main cause of morbidity and death from such disease. A functional characteristic of arteries that is changed under pathological conditions is their wall stiffness. Early diagnosis of such arterial alterations may identify individual risks to clinical complications, allowing retardation of the pathological process. Some examples of non-invasive methods of arterial stiffness assessment are the pulse wave velocity (PWV) and the pulse transit time (PTT). The present work proposes a PTT measurement system that estimates the time interval between the R wave of the QRS complex and the arrival of the pressure pulse wave at radial artery by using the bioimpedance technique to detect such arrival, instead of pressure transducers. Preliminary tests were made, taking two different points of the bioimpedance signal, and discounting or not the pre-ejection period. The PTT results, obtained from six volunteers, were on average close to the ones obtained by some other works using different techniques and measure points: 240 ms against 250 ms (literature) and 112 ms against 110 ms (literature). These values were collected by taking the interval between ECG peak and bioimpedance peak or bioimpedance maximum slope, respectively. Despite the need for more tests, the findings indicate that the system designed in this work may be used for arterial stiffness evaluation.