The impact of gender on outcome from mechanical ventilation

Objective: To determine the relation of gender to outcome for patients requiring mechanical ventilation. Design: A prospective cohort study. Setting: Medical and surgical ICUs in two university-affiliated teaching hospitals. Patients: Three hundred fifty-seven patients requiring mechanical ventilation. Interventions: Prospective patient surveillance and data collection. Measurements and results: The primary outcome measure was hospital mortality. Secondary outcome measures included need for reintubation, hospital and ICU length of stay, duration of mechanical ventilation, and hospital charges. The hospital mortality rate for women (n=189) was significantly greater than the hospital mortality rate for men (n=168) (28.0% vs 17.3%; p=0.016). This difference in hospital mortality was observed despite similar baseline demographic characteristics, severity of illness, indications for mechanical ventilation, and number of dysfunctional organ system in these two groups of patients. The duration of mechanical ventilation and ICU length of stay was also significantly longer for female patients compared with male patients (p≤0.056). In a logistic-regression analysis, female gender was found to be independently associated with hospital mortality (adjusted odds ratio [AOR]=2.38; 95% confidence interval [CI]=1.70 to 3.35; p=0.010). The presence of ARDS (AOR = 10.69; 95% CI=5.86 to 19.51; p<0.001), the number of dysfunctional organ systems (AOR=2.07; 95% CI=1.78 to 2.41; p<0.001), Acute Physiology and Chronic Health Evaluation (APACHE) II predicted mortality (AOR=1.15; 95% CI=1.11 to 1.19: p<0.001), and patient age (AOR = 1.04; 95% CI=1.03 to 1.06; p<0.001) were also found to be independently associated with hospital mortality. The number of dysfunctional organ systems present at the start of mechanical ventilation was the major independent predictor of hospital mortality (54% of total explanatory power). Patient gender was the least important independent predictor of hospital mortality (5% of total explanatory power). Conclusions: In this patient cohort, women requiring mechanical ventilation were at greater risk for hospital mortality than men. Physicians should be aware that outcome differences according to gender can occur when evaluating or designing clinical trials involving mechanically ventilated patients. Future studies are necessary to determine the general applicability of these findings and to identify explanations for such observed gender-specific differences in outcome.