The effect of underwater exercise on respiratory resistance (Rrs) was examined in 12 patients with chronic obstructive pulmonary disease (COPD). Rrs was measured while the patients were sitting on land with quiet respiration, while immersed in water (at 38°C) up to the upper abdomen and upper chest in standing position, and while sitting on land with quiet respiration after mild underwater exercise. The mean Rrses in each condition were 0.37, 0.37, 0.42, 0.33kp/1/s. Rrs increased by 14% (p<0.005) after immersion in water up to the upper chest and decreased by 12% (p<0.001) after underwater exercise. The change after exercise showed a popitive correlation with FEV_1.0/FVC on spirogram. Although water immersion or underwater exercise of these COPD patients caused a slight load in ventilation, no significant aggravation of the subjective symptom was found.
The above results suggested that uoderwater exercise was beneficial as a physical treatment for mild cases of COPD.