LUNG FUNCTION STUDIES. V. RESPIRATORY DEAD SPACE IN OLD AGE AND IN PULMONARY EMPHYSEMA 1

Abstract

Continous measurements were made of N2 concn. and volume-flow of gas expired after O2 inhalation. During one expiration, N2 concn. successively equals inspired concn., increases in an S-shaped fashion, and is rectilinear. Studies on subjects with pulmonary disease and uneven alveolar ventilation indicate the linear phase of N2 concn. is present and represents alveolar gas, thereby permitting dead space measurement. Semi-reclining, the mean dead space and dead space/tidal volume fractions were 127 ml. and 22.6% in 10 young men, 150 ml. and 24.9% in 11 old men, 169 ml. and 24.7% in 9 old men with marked emphysema. After maximal inspiration, avg. dead space values of about 225 ml. were found in all groups.