The effects of head-out-of-water immersion on arterial wave reflection in healthy adults

Abstract 

Swimming/hydrotherapy produces hemodynamic and physiological changes related to water immersion (WI). To evaluate the effects of head out (HO) WI on central hemodynamics, we prospectively studied 21 healthy subjects (62% male, age 37 ± 13 years). Central aortic blood pressures (CA-BPs) and reflected wave properties were evaluated using applanation tonometry at baseline and upon 2 minutes of waist (W) and mid-chest (C) HOWI. Heart rate (HR) decreased from 83 ± 15 to 73 ±10 beats/min (P < .001). Brachial artery pulse pressure (PP) was unchanged (45 ± 11 to 46 ± 7 mm Hg; P = .20), CA-PP increased stepwise (27 ± 7 to 32 ± 8 to 33 ± 6 mm Hg; P < .001). Reflected wave amplitude (P_s − P_i), and HR-corrected augmentation index (AI_a@75) increased stepwise from baseline-W-C level HOWI [(P_s − P_i): 2 ± 3 to 7 ± 4 mm Hg, P < .001; AI_a@75: 8 ± 11 to 19 ± 10%; P < .001]. HR-corrected ejection duration (ED_c) and reflected wave systolic duration (Δt_r) increased progressively (ED_c: 389 ± 23 to 408 ± 25 to 435 ± 13 milliseconds; P < .001; Δt_r: 106 ± 32 to 165 ± 21 ms; P < .001). Indices of left ventricular (LV) workload including wasted LV energy subendocardial viability and tension time index increased upon HOWI. HOWI increases the amplitude and the duration of the reflected aortic pressure wave, increases wasted LV pressure energy, workload, and oxygen demand.

Keywords: Central aortic blood pressure, hemodynamics, left ventricular, aortic stiffness