Sex related differences in applied tidal volume with flow-controlled ventilation: a subgroup analysis.

Background: Flow-controlled ventilation (FCV) ensures a constant gas flow whereby precise determination of dynamic compliance is feasible. Accordingly, ventilator pressure settings can be adjusted to achieve the highest compliance. This setting will automatically adapt tidal volume to the functionally available lung volume as a personalized approach. This is in contrast to current ventilation settings, where fixed tidal volumes according to predicted body weight (PBW) are recommended. Aim of this subgroup-analysis was to determine whether applied tidal volume differs in male and female patients after compliance guided individualization of ventilation parameters.

Methods: A sub-group analysis of 24 patients randomized to receive flow-controlled ventilation in cardiac surgery was performed. Linear mixed-effects model was used in order to investigate sex related differences in respiratory parameters.

Results: Compliance guided pressure titration led to comparable pressure settings in male (N.=18) and female (N.=6) patients. In contrast, the applied tidal volume was significantly lower in female patients (8.6 vs. 9.9, 95% CI: -2.3 to -0.2 mL/kg PBW; P=0.029) compared to male individuals, due to a significantly lower compliance (49.3 vs. 70.3, 95% CI: -33.1 to -8.8 mL/cmH2O; P=0.003). Gas exchange parameters were comparable in either sex.

Conclusions: Female patients were found to receive lower tidal volumes after compliance guided individualization compared to men during cardiac surgery. This finding may indicate that the functionally available lung volume in women is lower and thus using PBW may not adequately comply with sex related differences, which supports the use of a personalized ventilation strategy.