Acute Effects of Short-Term Warm Water Immersion on Arterial Stiffness and Central Hemodynamics

Abstract

Warm water immersion (WWI) has a potentially favorable effect on vascular health. However, the effects of short-term WWI on vascular function and central hemodynamics remain unclear. The present study aimed to determine the acute effects of short-term WWI on arterial stiffness and central hemodynamics in healthy men. Ten healthy men (27-57 years, 44 ± 12 years of mean age) underwent 5-min WWI (40-41°C) at the heart level. Systemic hemodynamics and tympanic temperature were monitored during WWI. Furthermore, pulse wave velocity (PWV) and aortic hemodynamics were measured before and 10 min after WWI. Cardiac output (CO) (via the Modelflow method) increased (P = 0.037), whereas tympanic temperature did not change (P = 0.879) during WWI. After 5-min WWI, heart rate (HR) and brachial diastolic blood pressure (BP) were significantly decreased. Aortic and leg PWV were decreased by 7.5 and 3.1%, respectively (P = 0.006 and P = 0.040). Femoral arterial blood flow was increased by 45.9% (P = 0.002), and leg vascular resistance was decreased by 29.1% (P < 0.001). Regarding central hemodynamic variables (estimated by general transfer function), aortic BP and augmentation index (AIx) did not change significantly, but the subendocardial viability ratio (SEVR), an index of coronary perfusion, was increased (P = 0.049). Our results indicate that a short-term WWI acutely improves aortic and peripheral arterial stiffness and coronary perfusion. Further studies to determine the interaction between the residual effect of a single bout of short-term WWI and chronic change (e.g., adaptation) in arterial stiffness and central hemodynamics are needed.

Keywords: aortic hemodynamics; arterial stiffness; femoral arterial blood flow; pulse wave analysis; warm water immersion.

FIGURE 1

Schema of aortic pulse wave analysis. Augmentation pressure (AP) is the additional pressure added to the forward wave by the reflected wave. Augmentation index (AIx) is defined as the AP as a percentage of pulse pressure. The dicrotic notch (DN) represents the closure of the aortic valve and is used to calculate ejection duration. Aortic tension-time index (TTI) and diastolic pressure-time index (DPTI) reflect the myocardial oxygen demand and the blood supply to the heart, respectively. These are calculated as the areas under the curve of aortic pressure waveform in systole and diastole, respectively. The subendocardial viability ratio (SEVR) is the ratio of DPTI to TTI.

FIGURE 2

(A) Aortic tension-time index (TTI), (B) diastolic time-pressure index (DPTI), and (C) subendocardial viability ratio (SEVR) before and after warm water immersion. Circles and error bars are mean and SD. Gray lines indicate individual changes.

FIGURE 3

(A) Aortic and (B) leg pulse wave velocity (PWV) before and after warm water immersion. Circles and error bars are mean and SD. Gray lines indicate individual changes.

FIGURE 4

Femoral (A) arterial blood flow (BF) and (B) leg vascular resistance (VR) before (PRE) and after (POST) warm water immersion. Circles and error bars are mean and SD. Gray lines indicate individual changes.

FIGURE 5

Relation. of change in leg pulse wave velocity (PWV) with corresponding changes in femoral arterial (A) blood flow (BF) and (B) shear stress (SS).