Hypotensive and circulatory effects of artificial CO2 bathing (Bub-KAO bath) in normal and hypertensive men / 日本温泉気候物理医学会雑誌

ABSTRACT

Bub-KAO tablet (50g) consisting of equimolar bicarbonate salt and succinate made it possible to use easily CO₂ bath at home. Since the obtained CO₂ concentration was not so high, we studied the circulatory effects of usual concentration of Bub-KAO bath in normal and hypertensive men.<br>Seven Bub-KAO tablets (KAO Co., Tokyo, Japan) were put into 350 l of 41°C simple hot spring bath (CO₂ conc. ≈300ppm). Eight normotensive subjects (32.2±4.2yrs) and 13 hypertensive patients (67.8±11.3yrs) took this artificial CO₂ bath for 10min. As a control, 12 normotensives (38.1±8.8yrs) and 12 hypertensives (51.0±8.2yrs) were immersed in 41°C simple hot spring bath for 10min. Hemodynamic functions and blood gas were followed before and after bathing for 30min in the supine position.<br>In normotensives, blood pressure (BP) was unchanged either by Bub-KAO or simple bath. The increase in heart rate (HR) and cardiac output (CO) and the decrease in total peripheral resistance (TPRi) after Bub-KAO bath were slightly but significantly greater than those of simple bath. In hypertensives, BP was significantly decrased after Bub-KAO bath (-17.2±6.4/-6.8±2.1mmHg) compared to simple bath. Although the increase in HR and CO (+0.55±0.22l/min) after Bub-KAO bath were not so remarkable, decrease in TPRi (-9.3±3.6 unit) was significantly greater than simple bath. Venous blood obtained 10min after Bub-KAO bath became fresh red showing a significant increase in pO₂ and pH (alkalosis) and significant decrease in pCO₂. In arterial blood, although pO₂ was unchanged, slight decrease in pCO₂ and increase in pH were also observed.<br>These results indicated that artificial CO₂ bath made by usual amounts of Bub-KAO tablets significantly reduced BP of the hypertensives due to vasodilating effect. Vasodilation by CO₂ bath was considered to be derived from the peripheral action of CO₂ as blood pCO₂ was rather reduced. As a basic mechanism of vasodilation by CO₂, we proposed the inhibitory effect on tissue enerqy metabolism of CO₂ as a product inhibtor of TCA cycle and subsequently, the onset of vascular autoregulation mechanism.