Regional difference of respiratory changes in pleural pressure between left and right thoraxes in dogs.

Respiratory changes in pleural pressure were recorded simultaneously from the left and right pleural spaces in 6 anesthetized closed-chest dogs in the supine, prone, left lateral and right lateral positions. Saline-filled radiopaque catheters connected to strain-gauge manometers were inserted percutaneously in the left and right pleural spaces by an air tight technique and their tips were placed in the mid-thoracic plane. The esophageal pressure was also recorded with the saline-filled system. The value of respiratory pressure amplitude (deltap, the difference between end-expiratory and minimal inspiratory pressures) in the pleural spaces was significantly greater in the left thorax than in the right in the supine, prone and right lateral positions. In 4 body positions, deltap in pleural pressure was significantly greater than in esophageal pressure. It is concluded that respiratory variations in pleural pressure of the left and right thorax are not the same and that postural change does not produce significant regional difference of the respiratory variations.