Higher Class of Obesity Is Associated With Delivery of Higher Tidal Volumes in Subjects With ARDS.

BACKGROUND: Obese subjects are at higher risk of development and progression of ARDS. There are limited data regarding mechanical ventilation practices and use of adjunctive therapies in subjects with ARDS across different obesity classes. We hypothesized that the adherence to lung-protective ventilation would be worse with rising body mass index class in patients with ARDS. METHODS: We conducted a retrospective observational study of subjects with ARDS. We evaluated the differences in ventilator settings, airway pressures, gas exchange, use of rescue therapies, length of hospital stay, and mortality among subjects based on the obesity classes of the WHO. RESULTS: The study included 613 subjects with ARDS: 21.4% were normal weight, 25% were overweight, and 53.7% were obese; 33.3% of the obese subjects met criteria for class I-II obesity, while 20.4% were class III obese (morbid obesity). On day 1, 53% of subjects with class III obesity had tidal volumes > 8 mL/kg, compared to 26% of the subjects with normal weight. In addition, 48% of the morbidly obese subjects received at least one rescue therapy as compared to 37% of normal weight subjects and 36% of overweight subjects. There were significant differences in the use of rescue therapies among the groups. In a multivariable model, subjects with class III obesity were significantly more likely to receive tidal volume > 8 mL/kg predicted body weight on day 1 when compared with subjects with normal weight (odds ratio 3.14, 95% CI 1.78-5.57). There was no difference in length of stay in ICU or hospital, duration of mechanical ventilation, or adjusted ICU or hospital mortality among the 4 groups. CONCLUSIONS: In this study, the risk of exposure to higher tidal volumes and the need for specific rescue therapies rose with higher classes of obesity in subjects with ARDS. More research is needed to identify how to better implement lung-protective ventilation in patients with obesity.