Diaphragm dysfunction and respiratory insufficiency after upper abdominal surgery.

This study was designed to determine the contribution of diaphragm dysfunction and pain to respiratory insufficiency after upper abdominal surgery. Respiratory insufficiency and postoperative pain in humans were evaluated by pulse oximetry, pulmonary function tests, and a visual analog scale. Diaphragm shortening in dogs was evaluated with biplane videoroentgenography. In humans, despite reasonable pain control, pulmonary function, as reflected in forced vital capacity (FVC), forced expiratory volume in one second (FEV1) and arterial oxygen saturation (SpO2) were significantly reduced on the first postoperative day. Improved pain control was not associated with improvements in FVC or FEV1. In the dogs, diaphragm shortening and tidal volume were significantly reduced in the immediate postoperative period. Phrenic nerve stimulation immediately after surgery resulted in supramaximal diaphragm shortening, which indicated neither the diaphragm nor phrenic nerves were significantly injured by surgical manipulation. Diaphragm dysfunction has a major role in postoperative pulmonary insufficiency; an afferent-mediated reflex inhibition of the phrenic nerves may be responsible.