The predicted body weight equation overestimates lung sizes of female, critically ill patients: an analysis of randomized, controlled trials and real-world clinical data.

PURPOSE: Low tidal volume (Vt) ventilation is the standard of care among critically ill patients. Guidelines recommend scaling Vt to the predicted body weight (PBW) to avoid ventilator-induced lung injury (VILI). Concerns exist that the PBW overestimates lung volumes of critically ill females. We investigated whether this applies to clinically relevant measures of lung volume, whether PBW-guided mechanical ventilation yields comparable risk of lung stress among male and female patients, and whether this affects mortality.

METHODS

Mechanically ventilated, critically ill patients from ten randomized trials and two real-world retrospective clinical datasets were analyzed. Risk of high driving pressures (≥ 15 cmH2O) at comparable Vt/kg PBW as well as measures of anatomical and functional lung sizes, including computed tomography-measured lung volumes at the same PBW were compared between female and male patients.

RESULTS

Among 30,516 patients (39.4% female), ventilation with comparable tidal volumes standardized to PBW (ml/kg PBW) was associated with 4.2% (95% CI 3.2-5.3; aOR 1.26, 95% CI 1.19-1.33; p < 0.001) higher absolute risk of high driving pressures among females, mediating 8.4% of excess 28-day mortality (p < 0.001). At the same PBW, female patients had lower anatomical and aerated lung volumes (- 343 ml, 95% CI - 449 to - 237, p < 0.001; and - 188, 95% CI - 282 to - 94, p < 0.001, respectively) than males.

CONCLUSIONS

The widely used PBW equation overestimates lung volumes in female critically ill patients, resulting in excess risk of injurious driving pressures among females, mediating higher mortality. Personalized mechanical ventilation by using driving pressure-guided strategies might mitigate these disparities.