[Effects of bathing on lung mechanics in patients with severe COPD]

Although it is well known that the majority of patients with severe COPD complain of exacerbated dyspnea while taking a Japanese-style bath, the mechanism has not been elucidated. We therefore investigated changes in lung volume (LV) and SaO2 in 16 seated patients with severe COPD, receiving treated with home oxygen therapy (HOT), and in 10 healthy subjects (C) immersed to the navel (N) and to the shoulder (S). We then subdivided the COPD patients into 2 groups, A and B. Group A was composed of patients taking less than 2 L oxygen/min, while group B was taking equal to or greater than 2 L oxygen/min. Expiratory reserve volume (ERV) decreased with statistical significance (p < 0.05) while inspiratory capacity (IC) substantially increased as immersion progressed. However, changes in LV were smaller, as obstructive ventilatory changes progressed. It also appeared that a significant O2 desaturation occurred in patients with COPD when movement was associated with taking a bath. The drop in SaO2 during bathing was significantly improved after patients received instructions concerning posture, slow movements, and pursed-lip breathing. These findings suggest that immersion, such as when taking a Japanese-style bath, 1) may change various LV to a lesser degree than in healthy subjects because of previously existent airway obstruction in COPD, 2) may aggravate arterial desaturation through further impairment of the VA/Q imbalance, 3) instructions for COPD patients could improve, their condition while bathing and, 4) the 6 minute walking distance (6 MD) might be important in predicting the severity of arterial desaturation while COPD patients are immersed.