It was found that no effect of increase in dermal blood flow depended solely on HCO₃^- or CO₃^2-, but on CO₂ gas dissolved in water.
The artificial CO₂ bath was prepared with sodium bicarbonate and citric acid, mixing simply in plain water at 38-40°C.
Thermal efficacy was confirmed by a rise in temperature of oral, finger tip and forehead respectively, and by a high transepidermal water loss (TWL) in consequence of increase in dermal blood flow, compared to a plain bathing.
A remarkable effect in artificial CO₂ bathing of 400-800ppm has been well-known clinically, however, a substantial increase in dermal blood flow has observed with artificial CO₂-bathing of 59.8ppm or greater in this study, so that a CO₂-bathing using the preparation would be popularized.