A CONCEPT OF MEAN ALVEOLAR AIR AND THE VENTILATION—BLOODFLOW RELATIONSHIPS DURING PULMONARY GAS EXCHANGE

Abstract

An equation is derived which expresses all theoretically possible alveolar gas concns.in terms of an alveolar ventilation/bloodflow ratio. If the mixed venous blood gas tensions, the inspired gas tensions and the R.Q. are known, a theoretical mean alveolar air concn. can be defined. Evidence is presented to show that the alveolar air sampled automatically from the end of a normal tidal vol. is probably in closer agreement with the theoretically defined mean alveolar air than a sample obtained by the Haldane method. The effect of unequal blood flow and unequal ventilation upon the alveolar-arterial oxygen gradient is discussed.