Effects of Hypoxic and Cool Environmenton Pulmonary Diffusing Capacity for CO

Abstract

The purpose of this study is to examine whether ambient temperature affects change in pulmonary diffusing capacity for carbon monoxide caused by hypoxia.Five male young adultswere exposed to the simulated altitude of 0, 2000, and 4000 m.Pulmonary diffusing capacityduring rest and exercise was tested in four different ambient temperatures of 16, 20, 24, and 28°C in each altitude.There was no temperature effect on diffusing capacity at sea level.However, at 2000 and 4000 m, diffusing capacity in a cool environment below 20°C wasincreased significantly compared with that in 28°C during rest and mild exercise(300kgm/min).Diffusing capacity during hypoxia was predicted, which was presumed that pulmonarycapmary blood volume was the same one at sea level.As aresult of comparison betweenmeasured and predicted value at high altitude, there were no differences on every occasions at 2000m, while significant increase in measured diffusing capacity was observed in a coolenvironment during rest and mild exercise at 4000m.It was implied that gas exchange surfacearea was increased during hypoxia in a cool environment caused by increase in capinary bloodvolume in itself and/or change in distribution of capinary blood flow in the lungs.However, these effects were relatively reduced at either ambient temperature above 24°C or work rateabove 300 kgm/min.It was concluded that a degree of hypoxic effects on pulmonary diffusingcapacity were related closely to ambient temperature and energy expenditure and that theseeffects became larger in a cool environment during rest at higher altitude.