Abstract 602: Determinants of Elevated Blood pressure with Water Immersion

Abstract

Introduction ; Although exercise in water is appreciated in rehabilitation for patients with renal disease and obesity individuals with knee joint pain, elevated blood pressure (BP) is also induced by water immersion via water pressure. This elevation of BP in water may lead to incidence of acute heart diseases in rehabilitation exercise. It is important for prevention of such acute event to understand determinants of elevated BP with water immersion. Hypothesis ; We assessed the hypothesis that elevated BP with water immersion is affected by venous volume or baroreflex sensitivity (BRS) as well as age or arterial stiffening, because blood pressure is associated with venous return (contributing cardiac output) or vascular functions. Methods ; Thirty-eight young (21.2 ± 1.7 yrs) and 20 older (65.1 ± 3.2 yrs) men participated in this study. In all subjects, mean BP (oscillometric method), pulse wave velocity adjusted by BP (cardio-ankle vascular index: CAVI), venous volume (by using MRI and plethysmography), and BRS by using valsalva maneuver were measured at resting supine position on land. Furthermore, BP and heart rate at standing position on land and following in water (located surface of water at epigastrium) were determined. Results ; On land, mean BP and CAVI were greater, and BRS was smaller in older men compared with young men. There was no different venous volume between 2 age groups. Change in increased systolic BP with water immersion was greater in older men (127 ± 12 mmHg → 145 ± 18 mmHg; P<0.05) than in young men (118 ± 129 mmHg → 129 ± 10 mmHg; P<0.05) (Interaction; P<0.05). Multiple-regression analysis revealed that the change in increased systolic BP with water immersion were independently associated with CAVI (beta = 0.406), when entering BRS, heart rate, venous volume, and CAVI. Conclusion ; In conclusion, these results of the present study suggests that arterial stiffening may contribute to elevated BP with water immersion, but not BRS or venous volume.