ABSTRACT
An experiment was conducted to investigate the effects of bathing in artificial CO<sub>2</sub> spa water (CO<sub>2</sub> 260ppm, at 38°C for 10 minutes) on the autonomic nervous system of man in comparison with those of bathing in plain water. The heart rate, coefficient of variation of R-R intervals of ECG (CV<sub>RR</sub>), blood pressure, and pulse wave were measured, and dynamic autonomic nervous function tests as described by Nishijo et al. were performed on eight gealthy volunteers (female).<br>The results obtained showed that the heart rate and height of pulse wave increased and blood pressure decreased during bathing both in artificial CO<sub>2</sub> spa water and plain water. However, the systolic blood pressure increased after bathing in plain water but did not increase after bathing in artificial CO<sub>2</sub> spa water. Though CV<sub>RR</sub> decreased during and after bathing in plain water, it did not decrease after bathing in artificial CO<sub>2</sub> spa water. Furthermore, the related degree of sympathetic and parasympathetic nervous functions increased after bathing in artificial CO<sub>2</sub> spa water (as measured after 40 minutes and 50 minutes). These results suggest that bathing in artificial CO<sub>2</sub> spa water can enhance the functions of the autonomic nervous system.