Mechanical power of ventilation and survival in critically ill obese patients

Obesity complicates mechanical ventilation due to altered respiratory mechanics, raising the risk of ventilator-induced lung injury (VILI). Mechanical power (MP) quantifies the energy transferred from the ventilator to the lungs per unit time, incorporating factors such as tidal volume, airway pressures, respiratory rate, and PEEP. The role of mechanical power as a predictor of outcomes in critically obese patients remains uncertain.

This retrospective cohort study analyzed data from the MIMIC-IV database, including 1860 obese patients (BMI ≥ 30 kg/m²) on mechanical ventilation for at least 48 h. Mechanical power was calculated over the first and second 24-h intervals, with time-weighted averages considered. Logistic regression, propensity score matching, and inverse probability of treatment weighting were employed to assess the relationships between mechanical power and hospital mortality.

A total of 1860 patients were included in the final analysis, of whom 539 (29.0 %) experienced in-hospital mortality. The median mechanical power during the second 24 h of ventilation was 15.50 J/min [10.54, 21.45], while the time-weighted average mechanical power was 16.12 J/min [11.75, 20.94]. No significant association was found between mechanical power during the second 24 h of ventilation and hospital mortality (OR 0.99, 95 % CI 0.97-1.00). However, time-weighted average mechanical power was associated with hospital length of stay (OR 0.98, 95 % CI 0.96-1.00). Additionally, the duration of mechanical ventilation emerged as a significant predictor of hospital mortality, whereas mechanical power alone did not significantly impact ICU or 28-day mortality.

Mechanical power did not predict hospital mortality in critically ill obese patients, suggesting the need for tailored ventilatory strategies focusing on both mechanical power and exposure duration.