An index of alveolar ventilation

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Abstract
An alveolar ventilation index (IAV) is proposed which is calculated on the basis of nitrogen-elimination experiments of the multiple-breath type and which is independent of volume measurements. For its calculation the number of breaths and the sum of nitrogen percentages in end-tidal air are needed. The index figures are related to a standardized reference system which permits comparison of alveolar ventilation under different experimental conditions. The method is discussed with special reference to such problems as mean alveolar concentration, asynchronous emptying of unequally ventilated parts, and disturbance by tissue nitrogen. A limited number of experimental results is presented. The IAV was tried for reproducibility and susceptibility to various factors presumed to cause changes in alveolar ventilation. For comparison, part of the material was also analyzed with the lung clearance index.