Effects of intermaxillary fixation during orthognathic surgery on respiratory function after general anesthesia.

I examined the relationship between preoperative breathing route (nasal and/or oral) and respiratory status in 29 patients who underwent orthognathic surgery and intermaxillary fixation (IMF) with general anesthesia and in 14 healthy, adult control volunteers who received IMF without surgery or anesthesia. The tidal volume (VT), minute respiratory volume (MV), respiratory rate, and end-tidal carbon dioxide concentration were measured for both nasal and oral breathing before and after IMF. Pulse oximetry recordings were also taken. There was no significant effect of IMF on any parameter in the volunteers. Fifteen patients engaged in nasal breathing only both before and after surgery with IMF (group pN), and 7 patients had combined nasal and oral breathing before but only nasal breathing after IMF (group pNO). VT and MV decreased (536-357 mL and 7.84-5.40 L, respectively) in group pNO after IMF. These results suggest that assessment of the preoperative breathing status is helpful in predicting postoperative respiratory function after IMF and indicate that patients with preoperative mouth breathing require greater respiratory care after general anesthesia with IMF.