Effects of Unilateral Collapse of the Lung *

Since 1882, when Forlanini first offered a rationale for collapse in the treatment of pulmonary tuberculosis, numerous clinical and experimental studies attempting to define the physiological effects of collapse of one lung have appeared. Most of the evidence cited by Pinner' supported the clinical impression that unilateral pneumothorax did not interfere with total respiratory function provided a healthy contralateral lung was present. Coryllos and Birnbaum,' Dock and Harrison,' Andrus,' and Moore'8 presented evidence suggesting a diminution in the relative blood flow to a collapsed or atelectatic lung. Cournand' found the resting pulmonary artery pressures in five patients with therapeutic pneumothorax to be within normal limits. While clinical studies of therapeutic collapse"" have been complicated by the presence of pre-existing pulmonary disease, experimental studies" '9' 18 19 s8 have been complicated by the artificial conditions of acute experiments on heart-lung preparations or on anesthetized animals, and by the technical difficulties inherent in the production of a true unilateral collapse in experimental animals. Attempts to produce unilateral collapse in experimental animals have been all but abandoned since 1924 when Snyder' and Matas' showed that, because of bilateral equalization of intrapleural pressure in dogs and other animals with thin mediastinal septa, a unilateral pneumothorax cannot produce unilateral collapse as it does in humans. The purpose of the present study has been to investigate by modern methods the effects of a true unilateral collapse of the lung on the oxygenation of the blood, on the respiration and circulation of each lung, on the intrapleural pressure, and on the blood pressures of the lesser circulation. The experiments were done upon unanesthetized dogs under conditions of rest or moderate exertion.