Analysis of Daily Pressor Episodes using an Ambulatory Blood Pressure-Cardiac Output Monitor

点击翻译按钮获取中文摘要

Fifty four undergraduate males were measured mean blood pressure (MBP), cardiac output (CO), and peripheral vascular resistance (PVR) every 5 min using a 24-hr. ambulatory blood pressure-cardiac output monitor. They were asked to check three pressor episodes every an hour retrospectively using an activity diary.First, results on the 39 subjects, who participated on the present study once, indicated that the hemodynamic mechanisms of MBP elevations were mainly those due to increases in CO for conversation and those in PVR for TV watching and TV game. These results were in consistent with the previous findings on laboratory syress testing. Second, reproducibility of MBP reactivity (=MBP during the pressor episode/MBP during the preceding baseline) and of the hemodynamic mechanisms (=PVR reactivity/CO reactivity) were assessed for the above-mentioned three pressor episodes using the 15 subjects who participated on the monitoring twice. Correlation coefficients were 0.207 for conversation, 0.252 for TV watching, and 0.304 for TV game for the former. They were 0.283,0.366, and 0.412 for the latter, respectively. The modest correlations have been often obtained in the previous study which strictly controlled the experimental settings. Third, maximum entropy method (MEM) plus least squares method (MemCalc <encircledR>) was applied in order to determine a periodic structure of the 24-hr. MBP variations using the 39 subjects. Nearly a 24-hr., a 1.5-hr., and a 1.8-hr. MEM periods were extracted for the whole, awake, and sleep periods, respectively. The exponent n of the MEM power spectrum P (f) - 1/f^n was calculated to be -1.077, -0.449, and -0.421, respectively. Accordingly, the long-term 24-hr. variation seemed to be 1/f characteristic, whereas the short-term variability of about 1.5 hr. resembled white noise due to a diversity of activities.