Postoperative Behavior of the Diaphragm and Ribs in Dogs

For a few days after upper abdominal operations in man the thoracic parietes are characteristically altered. Both the diaphragm and the ribs are markedly elevated, so that the space occupied by the lungs is shorter and broader; also, the diaphragmatic and costal movements are much reduced. The cause of this has been assigned to several factors: tight surgical dressings about the abdomen, reflex spasm of the abdominal and intercostal muscles, reflex inhibition of the diaphragm, gastro-intestinal distention, and pneumoperitoneum. Clinical studies 1 , 2 , 3 have furnished very suggestive evidence, but opinions are still conflicting as to the chief cause. We felt that, if laboratory animals also present these postoperative changes, they would be better adapted than man to the study of the causes and principles involved. Therefore, standard upper abdominal operations were performed on a series of dogs, with the essential surgical circumstances the same as those used in man (except, of course, the confinement in bed), and the diaphragm and ribs were examined. Other series of dogs were used as controls.

Five dogs (Group I) were employed as follows: All were fed as usual on the morning of the first day. Six hours later, morphine and atropine were given by hypodermic, and 1 hour after that a perfectly symmetrical anteroposterior roentgenogram of the chest was made, the x-rays being centered over a point 10 cm. cephalad to the xiphoid, by a specially devised method. The exposure was made at the expiratory phase of quiet breathing (as the most comparable phase in these animals whose respiration cannot always be regularized as to the depth of inspiration). Fluoroscopy was then done to determine the range of motion of the diaphragm and ribs with deepest breathing, produced by putting on a mask and cutting down the airway to a point barely compatible with the ability of the dog to maintain adequate pulmonary ventilation.