Objective: To identify any possible relation between lower than predicted preoperative respiratory muscle function and the incidence of postoperative respiratory complications and death in elective thoracotomies and laparotomies of the upper abdomen. Methods: A prospective cohort study was conducted, in which 70 patients over the age of 18 were monitored in two similar hospitals. In the preoperative evaluation performed at admission, patients were classified as presenting respiratory muscle function (as determined by measurement of maximal respiratory pressures) > 75% of the predicted value (n = 50) or < 75% of the predicted value (n = 20). Patients were monitored until discharge. In both groups, the incidence of pneumonia was determined, as was that of acute respiratory failure, bronchospasm, prolonged mechanical ventilation, atelectasis, pleural effusion, pneumothorax and death. A comparative analysis was made between the groups, and relative risk was calculated. Results: In the study sample, the overall incidence of postoperative complications was 22.86% (16/70): 55% (11/20) in the group of patients presenting < 75% of the predicted value; and 10% (5/50) in the group of patients presenting > 75% of the predicted value. Patients in the < 75% of the predicted value group presented a relative risk of 5.5 (95% confidence interval between 2.19 and 13.82). Conclusion: Respiratory muscle function below the predicted value was found to be related with higher relative risk of postoperative complications in the surgical procedures studied.

Keywords: Postoperative complications; Thoracotomy; Laparotomy; Respiratory muscles; Respiratory insufficiency