Acute vascular effects of carbonated warm water lower leg immersion in healthy young adults

• DOI: 10.14814/phy2.13046
• Publication Date: 2016-12-06T20:20:18Z
• Authors: Shigehiko Ogoh; Ryohei Nagaoka; Takamasa Mizuno; Shohei Kimura; Yasuhiro Shidahara; Tomomi Ishii; Michinari Kudoh; Erika Iwamoto
• Keywords: Male; Leg; Blood Pressure; 3. Good health; Vasodilation; Random Allocation; Young Adult; 03 medical and health sciences; Carbonated Water; 0302 clinical medicine; Regional Blood Flow; Immersion; Humans; Cardiac Output; Original Research; Skin

Endothelial dysfunction is associated with increased cardiovascular mortality and morbidity; however, this dysfunction may be ameliorated by several therapies. For example, it has been reported that heat-induced increases in blood flow and shear stress enhance endothelium-mediated vasodilator function. Under these backgrounds, we expect that carbon dioxide (CO2)-rich water-induced increase in skin blood flow improves endothelium-mediated vasodilation with less heat stress. To test our hypothesis, we measured flow-mediated dilation (FMD) before and after acute immersion of the lower legs and feet in mild warm (38°C) normal or CO2-rich tap water (1000 ppm) for 20 min in 12 subjects. Acute immersion of the lower legs and feet in mild warm CO2-rich water increased FMD (P < 0.01) despite the lack of change in this parameter upon mild warm normal water immersion. In addition, FMD was positively correlated with change in skin blood flow regardless of conditions (P < 0.01), indicating that an increase in skin blood flow improves endothelial-mediated vasodilator function. Importantly, the temperature of normal tap water must reach approximately 43°C to achieve the same skin blood flow level as that obtained during mild warm CO2-rich water immersion (38°C). These findings suggest that CO2-rich water-induced large increases in skin blood flow may improve endothelial-mediated vasodilator function while causing less heat stress.