[Determination of total lung capacity from the thoracic roentgen image]

Formulas for calculation of total lung capacity from chest X-rays were compiled from literature. Using the total lung capacity measured by bodyplethysmography as reference, these formulas and several modifications were tested for usefulness. The product of lung area in the posterior-anterior X-rays and the largest diameter from sternum to the dorsal rib bow in the frontal X-rays was the most simple and exact roentgenological indicator of total lung capacity. 95%-confidence intervals for predictive values gained by this method revealed to be of similar range as for total lung capacity estimated by the gas dilution methods in comparison to bodyplethysmography.