Systolic Peak Detection in Acceleration Photoplethysmograms Measured from Emergency Responders in Tropical Conditions

Abstract

Photoplethysmogram (PPG) monitoring is not only essential for critically ill patients in hospitals or at home, but also for those undergoing exercise testing. However, processing PPG signals measured after exercise is challenging, especially if the environment is hot and humid. In this paper, we propose a novel algorithm that can detect systolic peaks under challenging conditions, as in the case of emergency responders in tropical conditions. Accurate systolic-peak detection is an important first step for the analysis of heart rate variability. Algorithms based on local maxima-minima, first-derivative, and slope sum are evaluated, and a new algorithm is introduced to improve the detection rate. With 40 healthy subjects, the new algorithm demonstrates the highest overall detection accuracy (99.84% sensitivity, 99.89% positive predictivity). Existing algorithms, such as Billauer's, Li's and Zong's, have comparable although lower accuracy. However, the proposed algorithm presents an advantage for real-time applications by avoiding human intervention in threshold determination. For best performance, we show that a combination of two event-related moving averages with an offset threshold has an advantage in detecting systolic peaks, even in heat-stressed PPG signals.

Comparison of Acceleration Plethysmogram Acquired Using Optical Signal and Pressure Signal

“…Strong negative correlation was observed between 'a' and 'b', while strong positive correlation was observed between 'a-c' and 'a-e'. Acquisition of PPG or PP from any site (not directly from heart) and its analysis can reveal accurate information related to cardiovascular system; such as BP, HR, RR, CT, ∆T and APG related various ratios [17,18]. P-value (with α=0.05) of t-paired test carried out on means of all the five ratios (b/a, c/a, d/a, e/a and (b-c-d-e)/a) is shown in Table 4.…”

“…However, noise is higher frequencies in the PPG/PP signal. The first-order derivative parameters (as shown in Figure 3) have a non-acceptable variation and therefore are generally not used and its main features are: [2,18]  ∆T: It is the peak-to-peak time which is related to the time taken for the pressure wave to propagate from the heart to periphery and back. ∆T is the time between the systolic and diastolic peaks in the PPG/PP signal.…”

“…The (b-c-d-e)/a index, increases with age and is useful for evaluation of vascular aging and for screening of arteriosclerotic disease. [7,12,18] …”

Discrimination between different degrees of coronary artery disease using time-domain features of the finger photoplethysmogram in response to reactive hyperemia

“…It is even possible to record the PPG without any direct contact with the skin surface [31]. The above advantages may explain why PPG technology has attracted much attention in clinical applications [32][33][34][35][36]. Among these, there have been attempts to assess the endothelial function and presence of CAD through PPG signal processing in the FMD test [26,28,29].…”

Development of an Acceleration Plethysmogram based Cardioid Graph Biometric Identification

“…The lower signal is the second derivative of a PPG. Also known as APG consisting of a, b, c, d and e waves [5].…”