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During physical exercise, pulse transit time (PTT), expressed as the interval between ventricular electrical activity and peripheral pulse wave, may provide a surrogate estimate for blood pressure by the use of specific calibration procedures. The objective of this study was to determine systolic blood pressure (SBP) values derived from the PTT method and from an established method of non-invasive continuous blood pressure measurement based on the volume clamp technique, and to compare their agreement with sphygmomanometry during exercise tests. In 18 subjects, electrocardiogram (ECG) and finger-photoplethysmography were continuously recorded during maximal cycle exercise tests. Intermittent and continuous blood pressure measurements were simultaneously taken using automated sphygmomanometry and a Portapres Model-2 device, respectively. PTT was calculated for each ECG R-wave and the corresponding steepest upstroke slope in the photoplethysmogram, and was transformed to a continuous blood pressure estimate using multipoint nonlinear regression calibration based on the individual subject's sphygmomanometer readings. Bland–Altman limits of agreement between PTT-derived SBP estimates and sphygmomanometer values were –24.7 to 24.1 mmHg, and between Portapres and sphygmomanometer SBP values were –42.0 to 70.1 mmHg. For beat-to-beat SBP estimation during exercise, PTT measurement combined with multipoint nonlinear regression calibration based on intermittent sphygmomanometry may be an alternative to volume clamp devices. [ABSTRACT FROM PUBLISHER]

Obstructive sleep apnea ( OSA) is generally considered an etiologic factor in the development of hypertension ( HT), but the exact pathophysiological mechanisms remain incompletely explained. Portapres continuous non-invasive blood pressure ( BP) measurement during polysomnography ( PSG) might be a powerful tool for future research to better understand these mechanisms. However, the effect of overnight Portapres BP monitoring itself on sleep is unclear. The aim of this study was to analyze the impact of Portapres BP measurement on sleep quality during PSG. In a matched groups design, 40 patients with treated or suspected, untreated sleep apnea underwent one overnight PSG either with or without simultaneous Portapres BP measurement. Twenty PSG recordings with additional Portapres monitoring and 20 gender and treatment matched control PSGs were investigated. Total recording time was significantly lower in the Portapres group than in the control group (414.6 vs 443.4 min, P = 0.046). No statistically significant differences were observed in arousal index (20.6 vs 23.3 events/h), total sleep time (312.0 vs 324.6 min), sleep efficiency (75.2 vs 73.9%), sleep onset latency (20.4 vs 22.2 min), REM-sleep (16.1 vs 15.0%) and slow-wave sleep (8.9 and 11.5%) between the Portapres and the control group. The results of this analysis suggest that Portapres BP measurement during overnight PSG does not have a clinically relevant impact on sleep quality and might therefore be a good diagnostic tool for future research on dynamic BP changes in sleep apnea. [ABSTRACT FROM AUTHOR]