Abstract
Pulse transit time (PTT) represents a potential approach for cuff-less blood pressure (BP) monitoring. Conventionally, PTT is determined by (1) measuring (a) ECG and ear, finger, or toe PPG waveforms or (b) two of these PPG waveforms and (2) detecting the time delay between the waveforms. The conventional PTTs (cPTTs) were compared in terms of correlation with BP in humans. Thirty-two volunteers [50% female; 52 (17) (mean (SD)) years; 25% hypertensive] were studied. The four waveforms and manual cuff BP were recorded before and after slow breathing, mental arithmetic, cold pressor, and sublingual nitroglycerin. Six cPTTs were detected as the time delays between the ECG R-wave and ear PPG foot, R-wave and finger PPG foot [finger pulse arrival time (PAT)], R-wave and toe PPG foot (toe PAT), ear and finger PPG feet, ear and toe PPG feet, and finger and toe PPG feet. These time delays were also detected via PPG peaks. The best correlation by a substantial extent was between toe PAT via the PPG foot and systolic BP [− 0.63 ± 0.05 (mean ± SE); p < 0.001 via one-way ANOVA]. Toe PAT is superior to other cPTTs including the popular finger PAT as a marker of changes in BP and systolic BP in particular.
Highlights
Interventions, they have been confined to a nimals[8], few healthy humans[9], or critically ill patients[5,6,7,10] who are often hypotensive and not reflective of the hypertension management population
The baseline (BL) ear, finger, and toe PATs were 126 ± 4, 269 ± 6, and 266 ± 5 ms, respectively. While these values are consistent with previous data[1], the comparable magnitudes of the finger and toe PATs may be in part due to a hydrostatic effect in the reclining subject
We compared cPTTs detected from ECG, ear, finger, and toe PPG waveforms in terms of tracking blood pressure (BP) changes induced by interventions in humans
Summary
Interventions, they have been confined to a nimals[8], few healthy humans[9], or critically ill patients[5,6,7,10] who are often hypotensive and not reflective of the hypertension management population. Larger studies of normotensive and hypertensive humans have been conducted, but they have mainly involved few or simple BP interventions[1,3,4]. Only exercise has been invoked wherein finger PAT is already known to decline with the parallel increases in systolic and diastolic B P1. The previous efforts have typically been limited to study of only finger PAT. We compared the cPTTs as markers of BP changes under a battery of nontrivial BP-varying interventions in a relatively large number of normotensive and hypertensive humans
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