Relationship between pulse transit time and blood pressure during cardiopulmonary exercise tests

Introduction: Pulse transit time (PTT), the interval between ventricular electrical activity and peripheral pulse wave, is generally assumed to be a surrogate marker for blood pressure changes. Although recent studies have affirmed the potential use of PTT in the diagnostic of sleep disorders and the monitoring of psychophysiological stress, little work has been published on the effect of physical exercise on PTT and results have been inconsistant. Aims: To analyse PTT and its relation to blood pressure during cardiopulmonary exercise tests. Methods: In 20 patients (mean age 51, range 14-82) in a cardiopulmonary unit, ECG and finger-photoplethysmography were continuously recorded during routine cardiopulmonary cycle exercise tests. PTT was calculated for each R-wave in the ECG and the corresponding steepest upstroke in the plethysmogram. For each subject the resulting PTT-curve was averaged in order to compensate sample rate- and movement-associated variation, and values were compared to systolic (sBP) and diastolic blood pressure (dBP) in 9 predefined measuring points including measurements at rest, during increasing and maximum exercise as well as during the recovery period. Results: Mean sBP and PTT at rest were 127 mmHg and 372 ms respectively, 197 mmHg and 287 ms under maximum exercise, and 132 mmHg and 365 ms during recovery. All subjects showed a significant, strong negative correlation between PTT and sBP (mean r=-0.97, range -0.99 to -0.93, p= Conclusions: These results indicate that PTT is a good potential surrogate measure for sBP during exercise.