BACKGROUND AND OBJECTIVES: The predictive index for discontinuing mechanical ventilation is a prognostic parameter. The objective of this study was to evaluate the use of the Tobin index before tracheal extubation in patients undergoing general anesthesia. METHODS: Eighty patients, 40 (50%) men and 40 (50%) women undergoing cholecystectomy under general anesthesia were analyzed. The mean age of the patients was 57.7 +/- 12.4 (33 to 82 years) and mean body weight was 70.85 +/- 11.07 (48 to 90 kg). Thirty-seven patients (46.2%) were smokers. The Tobin index was obtained through the relationship between respiratory rate and tidal volume in cycles/Liter/minute (c.L-1.min-1). Age, weight, smoking, anesthetic-surgical risk, duration of the procedure, expired tidal volume, and postoperative respiratory rate, length of time in the recovery room, intraoperative clinical intercurrences and severity of the clinical intercurrences after extubation were studied. Parametric and non-parametric statistical tests, and analysis of univariate and multiple logistic regression were used. RESULTS: Age (p = 0.019), body weight (p = 0.006), smoking (p = 0.014), anesthetic risk (p = 0.0001), tidal volume (p < 0.0001), respiratory rate (p < 0.0001), length of time in the recovery room (p < 0.0001), and post-extubation clinical intercurrences (p < 0.0001) had a significant influence in the Tobin index. The independent variables with risk of failure to wean included advanced age and elevated body weight (p = 0.023). CONCLUSIONS: Weaning patients off mechanical ventilation in the postoperative period with a Tobin Index > 80 c.L-1.min-1 and < 100 c.L-1.min-1 was associated with elevated risk of postoperative clinical intercurrences after extubation. Patients with a Tobin index > 80 c.L-1.min, advanced age and increased body weight were independent variables of risk of failure to discontinue mechanical ventilation.