Diaphragm function and respiratory response after upper abdominal surgery in dogs.

Decreased diaphragm activity has been demonstrated after cholecystectomy in humans (Am. Rev. Respir. Dis. 127: 431-436, 1983). To investigate the mechanism(s) of postoperative diaphragm dysfunction we have established a dog model. Three groups of mongrel dogs were studied under general anesthesia: six dogs received no surgery (control); nine dogs underwent upper abdominal surgery (cholecystectomy); and six dogs underwent lower abdominal surgery (pseudoappendectomy). Diaphragm function was assessed by changes in transdiaphragmatic pressure swings, the ratio of changes in gastric to esophageal pressure swings, and the ratio of changes in abdominal to rib cage diameters during quiet tidal breathing. In the upper abdominal surgery group there were significant postoperative decreases in all parameters of diaphragm function and an increase in minute ventilation and respiratory frequency. However, there were no significant postoperative changes in the parameters of diaphragm function in the control or lower abdominal surgery groups. These studies establish that general anesthesia is not responsible for the reduced diaphragm activity seen postoperatively and that diaphragm function is not affected by lower abdominal surgery in dogs.