VASODILATION IS THE PREDOMINANT FACTOR OF BLOOD PRESSURE LOWERING DURING DEVICE-GUIDED SLOW BREATHING– ANALYSIS BY WAVE SHAPE PARAMETERS OF PULSE WAVE ANALYSIS

Abstract

Objective: There is evidence that device-guided slow breathing with direct biofeedback of pulse arrival time (PAT) leads to favorable changes (increase) in PAT and blood pressure (decrease). Slow breathing modulates peripheral blood flow and may decrease blood pressure by vasodilation. The objectives of the study presented here was to identify hemodynamic mechanisms of the blood pressure lowering effect of device-guided breathing observed in a previously published study (Mengden Blood Pressure Monitoring 2023). Design and method: Patients with a systolic BP 130-160 mmHg or treated essential hypertension (21 females / 23 males) were trained to perform repeated and unattended device guided slow breathing exercises for 10 minutes and 5 minutes cool down over 5 days. Furthermore, they were skilled to perform a self-measurement of blood pressure before and after the breathing exercise using a validated upper-arm device. A simple device was used to measure pulse arrival time by electrocardiography and photoplethysmography connected with a smartphone or tablet to provide biofeedback. Using pulse wave analysis, time to systolic peak (tsys) and time to dicrotic notch (tnotch) were measured and normalized to RR interval, i.e., as tsys / tT and tnotch / tT. Results: Oscillometric self measured blood pressure showed a reproducible decrease in systolic blood pressure of 5 mmHg (p<0.01, SD 8 mmHg). Absolute tsys increased by 13ms (p<0.001, SD 36 ms) and relative tsys / tT increased by 0.013 (p<0.001, SD 0.033) by the end of the exercise compared to baseline after cooling down (15 min). Similarly absolute tnotch increased by 11ms (p<0.001, SD 31 ms) as well as relative tnotch / tT in total by 0.011 (p<0.001, SD 0.036) compared to baseline. Conclusions: The delayed arrival of the first pulse wave maximum and the prolonged ejection time after adjustment for heart rate can be assumed here as a surrogate of a decreasing afterload. It is thus evident from this perspective that vasodilation is an important factor of blood pressure lowering during device-guided breathing.