END-EXPIRATORY PLEURAL PRESSURES IN DOGS IN SUPINE AND PRONE BODY POSITIONS STUDIED WITHOUT THORACOTOMY.
Final rept. for 15 Jul 63-1 Nov 64,
MAYO CLINIC ROCHESTER MINN
Pagination or Media Count:
Intrapleural pressures were measured simultaneously by saline-filled catheters from 2 to 5 different sites in the potential right pleural space of nine anesthetized dogs while the animals were supported in the supine and prone positions by means of molded half-body casts. Intrapleural tips of the catheters were placed at heart level in the cephalad-caudad dimension at ventral retrosternal and dorsal paravertebral sites in the thorax. The site of each catheter tip was measured from biplane x-rays taken in each position. The average vertical distance between the dorsal and ventral catheter tips was 10.6 S.E. of Mean 0.3 cm. In the supine position, mean end-expiratory pressure at the superior ventral catheter tip was -11.9 0.7 cm. H2O as compared to -5.0 0.5 cm. H2O at the dependent dorsal site giving an average gradient of 0.64 0.04cm. H2Ocm. vertical distance between the two recording sites. The respective values in the prone position were -9.0 0.6 cm. H2O superior dorsal site 0.7 0.5 cm. H2O dependent ventral site gradient 0.91 0.05 cm. H2Ocm. vertical distance. The slightly positive value for retrosternal pleural pressure and the greater dorsal-ventral gradient, when in the prone position, may be due to the weight of the heart. During the increase in weight induced by acceleration, these pressures were multiplied roughly in proportion to the G level and the difference in gradient between the two body positions was maintained. Author