Does obesity impact on weaning from invasive ventilation: a secondary analysis of the WEAN SAFE study.

OBJECTIVE: To understand the impact of obesity on outcomes of weaning from invasive mechanical ventilation (MV). METHODS: The study population consisted of patients enrolled in the WEAN SAFE study. We defined 4 groups based on body mass index (BMI), namely: Normal weight (BMI 18.5-24.9 kg/m²), Overweight (BMI 25-29.9 kg/m²), Obesity Class I (BMI 30-34.9 kg/m²), and obesity classes II and III (BMI ≥ 35 kg/m²). The primary outcome was the rate of successful extubation in patients in each BMI group. Secondary outcomes included the ICU and hospital survival, and PEEP levels at time of weaning eligibility in patients in each BMI group. RESULTS: In the study population, 1728 (38.2%) were of normal weight, 1395 (30.8%) were overweight, 590 (13.1%) were class I Obesity, and 431 (9.5%) were obesity classes II and III. Patients with obesity were more likely to be female, to be a medical admission, and to have comorbidities. Patients with grade II-III obesity had lower levels of sedation, later timing of the first separation attempt, longer time to weaning success, they received more noninvasive ventilation post extubation, and they had a longer ICU stay. In contrast, weaning success, and ICU and hospital mortality rates were not different in obese patients. There was no independent relationship between obesity and weaning delay, weaning success, or with overall survival outcomes. Higher PEEP at weaning eligibility was associated with weaning failure in normal and overweight patients but not in patients with obesity. CONCLUSIONS: Patients with obesity had a more complex and longer weaning process, but obesity per se was not independently associated with adverse weaning outcomes.