PULSE ARRIVAL TIME CAN TRACK CHANGES IN SYSTOLIC BLOOD PRESSURE

Abstract

Objective: Automated cuff-based blood pressure (BP) monitoring is limited to intermittent measurements vulnerable to movement. Pulse arrival time (PAT), calculated using electrocardiography (ECG) and photo plethysmography (PPG), has shown promise for non-invasive, continuous BP monitoring. The precise relationship between BP parameters and PAT under varying conditions remains to be fully understood. This study aimed to investigate the correlation between PAT and BP under different exercise modalities. Design and method: Data was analyzed on 33 volunteers aged 18 years or older with and without hypertension. The test protocol consisted of isometric leg exercise, an incremental ergometer bicycle test and seated periods of rest before, in-between and after. PAT was measured with an easy-to-use chest belt consisting of a 1-channel ECG and PPG sensor. PAT was calculated and averaged using a gliding average over 200 cycles from the R-wave in the ECG signal to the foot of the PPG waveform. Reference BP was measured every minute manually with an aneroid sphygmomanometer. Systolic- and diastolic BP was recorded to the nearest second for optimal synchronicity. Results: Subjects were aged 42.3 ± 13.3 years, ranging from 18–70. 48.5% were males, 18.2% had a prior diagnosis of hypertension and 15.2 % used antihypertensive medication. Systolic- and diastolic BP at inclusion were 123.6 ± 16.1 and 76.4 ± 8.4 mmHg with ranges from 98–168 and 66–100 mmHg respectively. Pearson's correlation between systolic BP and PAT was -0.86 ± 0.08, -0.84 ± 0.14 and -0.81 ± 0.14 for the full protocol, isometric exercise and dynamic exercise respectively. Corresponding correlation for diastolic BP was 0.43 ± 0.31, -0.75 ± 0.20 and 0.39 ± 0.35. For diastolic BP, correlation with PAT was positive in most subjects for the full protocol (94%) and dynamic exercise (79%), and negative in all subjects for isometric exercise. Systolic BP showed negative correlation inn all subjects for all analyses. Figure 1 shows test protocol and results for one subject. Conclusions: The results suggest that pulse arrival time can track changes in systolic blood pressure. The relationships between diastolic blood pressure and pulse arrival time varied between exercise modalities and remains to be further elucidated.