LUNG FUNCTION STUDIES. VIII. ANALYSIS OF ALVEOLAR VENTILATION BY PULMONARY N2 CLEARANCE CURVES 12

Abstract

Measurements were made (Lilly N2 anf flow meters) on successive breaths during clearance of pulmonary N2 while breathing O2, of mean expired N2 concn., number of breaths, and tidal volume. The clearance curves (log N2 concn. versus number of breaths) were descr. and analyzed by equations for 1 or more chambers, ventilated simultaneously but at different turnover rates. The lungs, in healthy young and old persons and in patients with cardio-pulmonary disease, were, in varying degree, ventilated unevenly, i.e., certain regions are ventilated more rapidly than others. The volumes and respective ventilation rates of these several regions were detd., also avg. total alveolar ventilation rate. The extent of uneven ventilation, uninfluenced by magnitude of respiratory dead space, was expressed as pulmonary N2 clearance delay, and was increased in old age and lung disease. This agreed with estimates based on variation of N2 concn. of alveolar gas expired after a single max. inspiration of O2.