Effects of temperature and humidity in CO2 gas-baths on epidermal blood perfusion and transcutaneous oxygen partial pressure (tpO2)

Background: Whereas the older balneological literature clearly states that dry carbon dioxide baths cause an increase in epidermal blood perfusion that depends on temperature and humidity, more recent studies denied that CO2 gas-baths increase the transcutaneous oxygen partial pressure (tpO(2)). To shed some further light on this unclear situation, the effect of dry carbon dioxid baths with different humidity and temperature should be tested. Design: A placebo controlled clinical trial was carried out on 17 healthy male volunteers (avg. age 27.0+/-5.02 y) who received differently prepared CO2 baths (78% vol; 30 minutes duration) in random order (30 degreesC/75% r. h., 30 degreesC/100% r. h., 35 degreesC/75% r. h., 35 degreesC/100% r. h.); 10 of the test subjects receiving additionally a gas bath without CO2 at 30 degreesC/100% r. h. that was used as control. As primary outcomes skin perfusion (laser doppler-flowmetry) of both the exposed and non-exposed arms and the tpO(2) of the exposed arm were chosen. Results: Skin perfusion and tpO(2) increased significantly under carbon dioxide exposure whereas the non-exposed arm showed no change; both effects were dose-dependent. The gas bath without CO2 yielded no change in skin perfusion or tpO(2), respectively. Conclusion: We conclude that carbon dioxide gas baths indeed increase skin perfusion and transcutaneous oxygen partial pressure, and that the efficacy depends on the temperature and relative humidity.