A multicentre observational study of intra-operative ventilatory management during general anaesthesia: tidal volumes and relation to body weight.

We conducted an observational prospective multicenter study to describe the practices of mechanical ventilation, to determine the incidence of use of large intra-operative tidal volumes (≥10 ml.kg(-1) of ideal body weight) and to identify patient factors associated with this practice. Of the 2960 patients studied in 97 anaesthesia units from 49 hospitals, volume controlled mode was the most commonly used (85%). The mean (SD) tidal volume was 533 (82) ml; 7.7 (1.3) ml.kg(-1) (actual weight) and 8.8 (1.4) ml.kg(-1) (ideal body weight)). The lungs of 381 (18%) patients were ventilated with a tidal volume>10 ml.kg(-1) ideal body weight. Being female (OR 5.58 (95% CI 4.20-7.43)) and by logistic regression, underweight (OR 0.06 (95% CI 0.01-0.45)), overweight (OR 1.98 (95% CI 1.49-2.65)), obese (OR 5.02 (95% CI 3.51-7.16)), severely obese (OR 10.12 (95% CI 5.79-17.68)) and morbidly obese (OR 14.49 (95% CI 6.99-30.03)) were the significant (p ≤ 0.005) independent factors for the use of large tidal volumes during anaesthesia.