Effects of water temperature on pulmonary volumes in immersed human subjects

Abstract

Pulmonary volumes and capacities have been measured at three water temperatures (Tw = 25, 34, 40 °C) in standing subjects immersed up to the shoulders. The comparison of data obtained in air with those obtained in thermoneutral immersion (Tw = 34 °C) confirms the results previously published in several studies. The comparison of data obtained in immersion at different Tw shows: 1. 1. A significant decrease in vital capacity (VC) with bath temperature (VC 40 °C > VC 34 °C > VC 25 °C). The same decrease is observed in the inspiratory reserve volume (IRV) while the expiratory reserve volume (ERV), the residual volume (RV) and the functional residual capacity (FRC) do not vary. 2. 2. A significant decrease in maximum breathing capacity (MBC) with bath temperature (MBC 40 °C > MBC 25 °C). 3. 3. A significant increase in tidal volume (VT) in cold or hot water compared to thermoneutral water (V t40 °C >V t34 °C; V t34 °C < V t °C) during quiet breathing. Breathing frequency does not change, thus ventilation (V̇) follows the same evolution as V t. The relative abdominal (ABD) contribution to V t, estimated by a double belt inductance plethysmograph, is reduced at T w = 25 °C but unchanged at T w = 40 °C compared to thermoneutral bath. Beside variations in the metabolic state, the variations of the pulmonary volumes as a function of T w are estimated to be mainly due to alterations in respiratory muscles functioning.