Differential ventilation in unilateral pulmonary artery occlusion.

A case is reported of complete isolated occlusion of the right pulmonary artery resulting in underperfusion of the right lung; this was confirmed radiographically and at thoracotomy. Bronchospirometry showed that there was a reduction of ventilation to the right lung. When this lung alone was supplied with a carbon dioxide rich mixture there was a shift of ventilation towards the normal pattern with reversion to the initial distribution when air breathing was resumed. Ventilation of the right lung with a low oxygen mixture failed to cause any shift of ventilation. The results confirm that the effects of pulmonary artery occlusion on differential ventilation which have been shown in animals also occur in man and provide further evidence that carbon dioxide can have a bronchodilator action in man.