Ventilation with low tidal volumes during upper abdominal surgery does not improve postoperative lung function.

BACKGROUND: Prolonged postoperative decrease in lung function is common after major upper abdominal surgery. Evidence suggests that ventilation with low tidal volumes may limit the damage during mechanical ventilation. We compared postoperative lung function of patients undergoing upper abdominal surgery, mechanically ventilated with high or low tidal volumes.

METHODS: This was a double-blind, prospective, randomized controlled clinical trial. One hundred and one patients (age ≥ 50 yr, ASA ≥ II, duration of surgery ≥ 3 h) were ventilated with: (i) high [12 ml kg(-1) predicted body weight (PBW)] or (ii) low (6 ml kg(-1) PBW) tidal volumes intraoperatively. The positive end-expiratory pressure was 5 cm H(2)O in both groups and breathing frequency adjusted to normocapnia. Time-weighted averages (TWAs) of forced vital capacity (FVC) and forced expiratory volume in 1 s (FEV(1)) until 120 h after operation were compared (P<0.025 considered statistically significant). Secondary outcomes were oxygenation, respiratory and non-respiratory complications, length of stay and mortality.

RESULTS: The mean (sd) values of TWAs of FVC and FEV(1) were similar in both groups: FVC: 6 ml group 1.8 (0.7) litre vs 12 ml group 1.6 (0.5) litre (P=0.12); FEV(1): 6 ml group 1.4 (0.5) litre vs 12 ml group 1.2 (0.4) litre (P=0.15). FVC and FEV(1) at any single time point and secondary outcomes did not differ significantly between groups.

CONCLUSIONS: Prolonged impaired lung function after major abdominal surgery is not ameliorated by low tidal volume ventilation.