Outcomes of morbidly obese patients receiving invasive mechanical ventilation: a nationwide analysis

Abstract

Background: Critically ill, morbidly obese patients (BMI≥40 kg/m2) are at high risk of respiratory failure requiring invasive mechanical ventilation (IMV). It is not clear if outcomes of critically ill, obese patients are affected by obesity. Due to limited cardiopulmonary reserve, they may have poor outcomes. However, literature to this effect is limited and conflicted.

Methods: We used the Nationwide Inpatient Sample from 2004 to 2008 to examine the outcomes of morbidly obese people receiving IMV and compared them to nonobese people. We identified hospitalizations requiring IMV and morbid obesity using International Classification of Diseases, 9th Revision, Clinical Modification codes. Primary outcomes studied were inhospital mortality, rates of prolonged mechanical ventilation (≥96 h), and tracheostomy. Multivariable logistic regression was used to adjust for potential confounding variables. We also examined outcomes stratified by number of organs failing.

Results: Of all hospitalized, morbidly obese people, 2.9% underwent IMV. Mean age, comorbidity score, and severity of illness were lower in morbidly obese people. The adjusted mortality was not significantly different in morbidly obese people (OR 0.89; 95% CI, 0.74-1.06). When stratified by severity of disease, there was a stepwise increase in risk for mortality among morbidly obese people relative to nonobese people (range: OR, 0.77; 95% CI, 0.58-1.01 for only respiratory failure, to OR, 4.14; 95% CI, 1.11-15.3 for four or more organs failing). Rates of prolonged mechanical ventilation were similar, but rate of tracheostomy (OR 2.19; 95% CI, 1.77-2.69) was significantly higher in patients who were morbidly obese.

Conclusions: Morbidly obese people undergoing IMV have a similar risk for death as nonobese people if only respiratory failure is present. When more organs fail, morbidly obese people have increased risk for mortality compared with nonobese people.

Figure 1.

Trends in admission and invasive mechanical ventilation in morbidly obese people.

Figure 2.

Forest plot showing odds of mortality between morbidly obese patients undergoing mechanical ventilation when compared with nonobese people (reference). A, According to admission type. B, According to severity of illness (number of organ failures).