Effects of maxillomandibular fixation on respiration.

The effects of maxillomandibular fixation (MMF) on respiration were studied by measuring pulmonary function in 27 healthy volunteer subjects and in six post-operative patients who underwent MMF after sagittal split ramus osteotomies. In addition, airflow resistance of the mouth was measured in seven healthy subjects under MMF. In the healthy subjects, the ratio of forced expiratory volume in one second to forced vital capacity and peak expiratory flow rate were reduced by 22.9% and 52.1%, respectively, after application of MMF, indicating the presence of respiratory obstruction, whereas the ratio of forced vital capacity to predicted forced vital capacity, an indicator of restrictive respiratory defects, was not significantly affected. The obstructive type of respiratory defect was found to be the result of increased airflow resistance with MMF. The decrease of forced expiratory volume was greater in all postoperative patients than in the healthy subjects. The results indicate that careful preoperative and postoperative airway management is essential for the safety of patients undergoing MMF for the treatment of oral and maxillofacial conditions.