Pleural pressure as a function of body position in rabbits

Pleural pressure was measured at end expiration in spontaneously breathing anesthetized rabbits. A liquid-filled capsule was implanted into a rib to measure pleural liquid pressure with minimal distortion of the pleural space. Capsule position relative to lung height was measured from thoracic radiographs. Measurements were made when the rabbits were in the prone, supine, right lateral, and left lateral positions. Average lung heights in the prone and supine positions were 4.21 +/- 0.58 and 4.42 +/- 0.51 (SD) cm, respectively (n = 7). Pleural pressure was -2.60 +/- 1.87 (SD) cmH2O at 50.2 +/- 7.75% lung height in the prone position and -3.10 +/- 1.22 cmH2O at 51.4 +/- 6.75% lung height in the supine position. There was no difference between the values recorded in the prone and supine positions. Placement of the capsule into the right or left chest had no effect on the magnitude of the pleural pressure recorded in rabbits in right and left lateral recumbency (n = 12). Measurements over the nondependent lung were repeatable when rabbits were turned between the right and left lateral positions. Lung height in laterally recumbent rabbits averaged 4.55 +/- 0.52 (SD) cm.