Effects of unilateral pleural symphysis on respiratory system mechanics and gas exchange in anesthetized dogs.

Lateral thoracotomy with pleural abrasion and application of talc was performed on 8 adult beagle dogs. The dogs had no effusion detectable on roentgenogram at the time of study, and obliteration of the pleural space was later confirmed by autopsy. With the dogs under pentobarbital anesthesia, lung mechanics and gas exchange were studied before and 5 wk after surgery. Total lung capacity decreased to 78% of control value (p less than 0.05). After the operation, pressure-volume curves of the respiratory system were shifted down, along with significantly decreased compliance. Maximal flow at constant lung volume was not significantly increased. Arterial O2 and CO2 tensions were not significantly different. Rebreathing DLCO normalized for lung volume was unchanged. The slope of phase III of a single-breath nitrogen test was increased (p less than 0.05) after surgery. Unilateral surgical obliteration of the pleural space results in a pure restrictive pattern. It does not affect the gas exchange surface. The increase in the slope of phase III is suggestive of a nonhomogeneous distribution of ventilation.