[Influence of tidal volume on functional residual capacity during general anesthesia]

Ventilation with lower tidal volume improves outcome in acute respiratory distress syndrome (ARDS). However, it is questionable if ventilation strategy using lower tidal volumes created for patients with ARDS can be transferred to healthy patients undergoing general anesthesia. We assessed the effects of ventilation with lower tidal volumes and conventional tidal volumes on functional residual capacity (FRC) and Pa(O2)/FI(O2) (P/F) ratio in patients undergoing general anesthesia for upper abdominal surgery.

We studied 16 patients undergoing general anesthesia for upper abdominal surgery. Patients were randomized to ventilation with low tidal volume group (7 ml x kg(-1) predicted body weight n = 8) or conventional tidal volume group (10 ml x kg(-1) predicted body weight n = 8). We measured FRC and P/F ratio after induction of general anesthesia and start of surgery in both groups.

There were no differences in FRC and P/F ratio between ventilation with lower tidal volume group and conventional tidal volume group (P > 0.05), but peak airway pressures with conventional tidal volume group were higher than those with lower tidal volume group only after induction of general anesthesia (P < 0.05).

Lower tidal volumes are better than conventional tidal volumes in view of airway pressure and lung protective strategy during general anesthesia.