Obesity has been cited in literature to result in variable survival outcomes in critically ill patients. Studies have shown low body mass index (BMI) to be associated with increased mortality in these patients. Effect of BMI on weaning outcomes has received little attention. Obesity can result in increased work of breathing by decreasing thoracoabdominal compliance and causing an abnormal diaphragmatic position. This could result in difficulty in weaning from ventilatory support. The objective of this study was to determine the effect of BMI on weaning and survival outcomes in patients with ventilator-dependent respiratory failure.
We retrospectively studied 206 patients with ventilator-dependent respiratory failure admitted to a long-term acute care facility for weaning. Patients were divided into the following groups based on their BMI: Underweight (BMI<20); Normal (BMI 20-25); Overweight (BMI 25-30); Obese (BMI 30-40) and Morbidly Obese (BMI >40).The following data was abstracted: age, sex, BMI, weaning outcome (successful wean defined as being off ventilator>7 days) and survival outcome (alive or expired at discharge). Relation between BMI-subgroups and outcomes was determined by Chi-square test. Effect of BMI >20 and BMI <20 on outcomes was also determined. p<0.05 was statistically significant.
Of 206 patients, 52% were females and 48% males with a mean age of 66±16 years. Sixty-eight percent weaned; 72% survived. Twenty percent were underweight; 30% normal; 22% overweight; 20% obese; 8% morbidly obese. Weaning and survival outcomes of these patient-subgroups are shown in Table 1OutcomeBody Mass Index (kg/sq m)p<2020-2525-3030-40>40Weaned26/3941/6329/4731/4012/17Failed13/3922/6318/479/405/17>0.05Survived20/39**42/63***35/47*31/40*14/17>0.05Expired17/3918/6311/478/403/17*
= Number of patients transferred to acute facility.. Weaning and survival outcomes of patients with BMI<20 and >20 are shown in Table 2OutcomeBMI< 20 (n=39)BMI> 20 (n=167)pWeaned26113>0.05Failed1354Survived20 *122 **0.009Expired1740*
=2 patients transferred to acute facility..
Comparison between the five BMI-subgroups showed no significant difference in weaning and survival outcomes. However, patients with BMI <20 had a worse survival outcome, but no difference in weaning outcome, than those with BMI >20.
Obesity doesnot affect weaning or survival outcomes in patients with ventilator-dependent respiratory failure. BMI <20 can serve as a prognosticator for less favorable survival outcome (but NOT a less favorable weaning outcome) in these patients.
D. Datta, None.