Pulse Transit Time Variability on a Range of Heart Rates between Resting and Elevated States

This study investigated pulse transit time (PTT) variability and trends for a wide range of heart rates (HR). PTT is considered as a significant index for estimating vital signs such as blood pressure (BP) and arteriosclerosis. However, PTT is still not an accurate indicator of these vital parameters, because PTT changes over time and is influenced by several factors, such as BP, HR, and other cardiovascular variables. Previous research indicated a correlation between HR and PTT, but only under limited experimental conditions in which HR was adjusted through decreased respiration in a supine position, resulting in a relatively low HR. Hence, it is not clear whether correlations between PTT and vital parameters are maintained if HR increases. In this study, HR was increased before and after exercise, allowing analysis of PTT variability over a wide range of HRs. Results obtained from PTT and HR measurements indicated a high degree of correlation between these factors, with correlation coefficients ranging from -0.836 to -0.967. Moreover, the correlation trend between PTT and HR variability held even through changes in applied gravity achieved by shifting body positions.