A study of photoplethysmography intensity ratio in hypertension

Hypertension is one of the most common factors causes the death of cardiovascular disease, which may damage the artery wall and change the arterial function. The photoplethysmography(PPG) intensity radio (PIR), as a new indicator which was calculated by the light intensity of PPG, has been proved to be strongly correlated with the vascular tone function. Therefore, PIR becomes a potential predictive factor for hypertension. In this study, in order to investigate the relationship between blood pressure (BP) and PIR, a seven days experiment was performed on 30 subjects. The subjects were divided into two groups (normal control and hypertension) according to their BP level, features were extracted from the PPG signal from each trial and investigated including PIR, diastolic time, systolic time and heart rate. The results show significant difference of these features between these two groups, e.g., the mean PIR of patients with hypertension is 0.5169±0.3814, where it is 0.4066±0.2586 in normal control subjects. The results demonstrate that PIR is strongly associated with BP, which has the potential to provide a possible way for early hypertension prediction, and also may be a factor improving the accuracy of cuffless BP estimation.