Total lung capacity of baboons and humans determined by planimetry of radiographs

Total lung capacity and radiographic lung area of 25 young and 7 aged baboons (Papio cynocephalus) and seven nonsmoking young adult men were measured. For all subjects, total lung capacity and radiographic lung area raised to the 3/2 power were shown to be highly correlated (r = 0.995). The regression equation for this relationship was total lung capacity (ml) = 78 + 0.234 x radiographic lung area (1.5) (cm2). A more useful regression equation for predicting values of total lung capacity was found to be log total lung capacity = -0.3819 + 1.4153 x log radiographic lung area (r = 0.993), because the standard error of estimate remains a constant percentage of Y values (+/- 12%). Total lung capacity and radiographic lung area were also highly correlated with height, weight and arm span of young baboons and men (r greater than 0.92), but the lungs of aged baboons were disproportionately larger.