Oxygen Saturation and Hemoglobin Level in the Muscles of Hypertensive Patients during Exercise in Water

To clarify whether exercise therapy in a water environment is appropriate therapy for hypertensive patients, we investigated oxygen saturation and hemoglobin level in the vastus medialis muscle using a laser tissue blood oxygen monitor. Seven hypertensive patients (52 to 77 years of age, hypertensive group) and five healthy volunteers (44 to 69 years of aged, control group) participated in this study. Subjects maintained resting postures for about 5 minutes each in a standing position, a sitting position on a chair, a lying position out of water, and a position in water below the navel and to the chest level. Subjects performed flexion/extension movement of the knee joint (30 times/min) in and out of water. Oxygen saturation level (SaO2), oxygenated hemoglobin level (HbO2), deoxygenated hemoglobin level (HbD), and total tissue hemoglobin level (HbT) were measured in the muscle tissue. Blood pressure (BP) and pulse rate (PR) were monitored simultaneously. In the hypertensive group, SaO2 in muscle tissue in water was significantly increased compared with that in a standing position out of water (p<0.05), and returned to the level in the control group. HbD in the hypertensive group was significantly reduced in the position in water to the chest level compared to that in a standing position (p<0.05). In both groups, the ratios of HbD and HbO2 (O2/D ratio) was significantly increased in water environment compared with that out of water (p<0.05). The O2 /D ratio, which indicates oxygenation within the tissue, increased during exercise in water in the hypertensive group. This study demonstrated that oxygen saturation in the muscles of the hypertensive group was lower than that in controls out of water, but the level was increased in water. Our findings suggest that water provides a good exercise environment for hypertensive patients from the perspective of oxygen saturation in hypertensive muscle tissue.