The excretion of highly soluble gases by the lung in man

The excretion (E) of inert gases by the lung depends on, among other things, their blood-gas partition coefficients (lambda). According to conventional gas exchange models, E should increase with increasing lambda. However, recent models that take into account the tidal character of breathing and the buffering capacity of lung tissue predict that E will show a minimum in the range of large lambda values (lambda greater than 10). Further, this local minimum should shift to larger lambda values in exercise conditions as compared to rest conditions. The aim of this study is to verify this predicted behaviour of E. The experiments were carried out with seven healthy subjects at rest and at three work loads (50 W, 100 W and 150 W) on a bicycle ergometer. The behaviour of E was determined from the results of a simultaneous washin of four tracer gases: ethyl acetate (lambda approximately 75), acetone (lambda approximately 330), ethanol (lambda approximately 2000) and acetic acid (lambda approximately 20000). The washin lasted 4 min, and E was calculated from E = 1 - PE-/PI, where PI and PE- are the partial pressures of the tracer gas in inspired and mixed expired gas determined from the recordings obtained during the last minute of washin. PI and PE- were measured with a mass spectrometer. Comparison of the E values of the four gases shows that at rest a minimum value for E is found for acetone. In exercise conditions, however, the smallest E value is found for the more soluble ethanol or acetic acid.(ABSTRACT TRUNCATED AT 250 WORDS)