Abstract

The volume of air at a transpulmonary pressure (PL) of 25 cmH2O was measured in 28 emphysema-free and 39 emphysematous excised adult lungs and in the lungs of 53 infants and children. In the adult emphysema-free lungs, this volume (V25) was significantly correlated with body length in males but, corrected for body length, not significantly correlated with age in either males or females. V25 was on the average 20 per cent larger than predicted TLC in non-emphysematous lungs in vivo. The lungs were also inflated and fixed with formalin at a constant PL of 25 cm H2O and their volume measured (VL). Marked and variable underinflation compared to V25 occurred in the adult lungs and VL minus lung weight averaged 75% of V25 and 91% of predicted TLC. In infants and children, the ratio of VL minus lung weight to V25 averaged 1.08 with a range of 0.58 to 1.84. The larger the lungs, the smaller the ratio, suggesting that fixation played a role in producing the small VL. In the emphysematous lungs, a significant correlation between the degree of emphysema and V25 was found. However, a statistically significant increase in V25 only occurred when the emphysema grade was greater than 5.