Measurement of Intrapleural Pressure at Different Points in the Chest of the Dog

¹ From the Department of Surgery, The Johns Hopkins University School of Medicine, Baltimore, Maryland

By use of needles specially designed to insure patency and of special wells to prevent inadvertent introduction of air into the pleural space, intrapleural pressure was measured at two or more locations in each of 13 dogs. Pressures measured at points between the third and eighth interspaces varied one from another by no more than 1.0 cm H₂O and usually by less than 0.5 cm H₂O. Pressures measured at the apex were more negative at end of expiration and less negative at end of inspiration than those measured at the above mentioned points. In the diaphragmatic sinus the reverse situation was found.