Excess Body Weight Is Not Independently Associated with Outcome in Mechanically Ventilated Patients with Acute Lung Injury

2 March 2004 | Volume 140 Issue 5 | Pages 338-345

Background: Despite an epidemic of obesity among adults, the effect of excess body weight on outcome from critical illness is not well studied.

Objective: To examine the association between excess body weight and outcome in mechanically ventilated patients with acute lung injury.

Design: Secondary analysis of participants in trials of therapy for acute lung injury.

Setting: 10 U.S. medical centers that participate in the National Heart, Lung, and Blood Institute Acute Respiratory Distress Syndrome Network.

Patients: 902 mechanically ventilated patients who were enrolled in randomized, controlled trials of therapy for acute lung injury.

Intervention: Assignment to higher (12 mL/kg of predicted weight) or lower (6 mL/kg of predicted weight) tidal volume ventilation strategies with specified weaning protocols. Some patients also received ketoconazole, lisofylline, or placebo by factorial design.

Measurements: Mortality rate, rate of unassisted ventilation by day 28, and number of ventilator-free days.

Results: Indirect causes of lung injury, including trauma, were more common in obese patients. Overweight and obese patients had higher peak and plateau airway pressures before enrollment because of higher set tidal volumes. After risk adjustment, excess body weight was not associated with death, achievement of unassisted ventilation, or number of ventilator-free days. This lack of effect persisted with categorical or continuous measures of body mass index (BMI). We found no significant interaction between ventilator protocol assignment and BMI category.

Conclusions: After risk adjustment, overweight and obese patients with acute lung injury have outcomes similar to those of patients with normal BMI. The lack of interaction between ventilator protocol assignment and BMI suggests that patients with normal, overweight, or obese BMI benefit from lower tidal volume ventilation for acute lung injury.

*For members of the National Heart, Lung, and Blood Institute Acute Respiratory Distress Syndrome Network, see the Appendix.

Editors' Notes Context Although obesity poses many health risks, clinicians have been uncertain whether excess body weight adversely affects the outcomes of severe illnesses such as acute lung injury requiring mechanical ventilation. Contribution Among patients in a trial of mechanical ventilation strategies, obese patients and lean patients had similar mortality and ventilation outcomes. Implications Physicians should not assume that intubated obese patients fare worse than those who are of normal weight. Whether excess body weight puts patients at risk for poor outcomes in other types of critical illness is a subject for future study. –The Editors

 

Author and Article Information

From University of Colorado Health Sciences Center, Denver, Colorado.

Grant Support: Dr. O'Brien is supported by a training grant from the National Institutes of Health (T32-HL07085). Dr. Welsh is the recipient of a Veterans Affairs merit review award. Contract N01-HR 46054-64 from the National Heart, Lung, and Blood Institute supports the Acute Respiratory Distress Syndrome Network.

Potential Financial Conflicts of Interest:Consultancies: J.M. O'Brien (Medical Simulation Corp.); Honoraria: J.M. O'Brien (Eli Lilly).

Requests for Single Reprints: James M. O'Brien Jr., MD, Division of Pulmonary Sciences and Critical Care Medicine, 4200 East 9th Avenue, Box C-272, Denver, CO, 80262; e-mail, James.OBrien{at}uchsc.edu.

Current Author Addresses: Dr. O'Brien: Division of Pulmonary Sciences and Critical Care Medicine, University of Colorado Health Sciences Center, 4200 East 9th Avenue, Box C-272, Denver, CO 80262.

Dr. Welsh: Division of Pulmonary and Critical Care Medicine, Department of Veterans Affairs Medical Center, 111A 1055 Clermont Street, Denver, CO 80220.

Mr. Fish and Dr. Kramer: Division of Health Care Policy and Research, University of Colorado Health Sciences Center, 3570 East 12th Avenue, Suite 300, Box B-159, Denver, CO 80206.

Dr. Ancukiewicz: Department of Radiation-Oncology, Massachusetts General Hospital and Harvard Medical School, 55 Fruit Street, Boston, MA 02114.

Author Contributions: Conception and design: J.M. O'Brien, C.H. Welsh, M. Ancukiewicz, A. Kramer.

Analysis and interpretation of the data: J.M. O'Brien, C.H. Welsh, R.H. Fish, M. Ancukiewicz, A. Kramer.

Drafting of the article: J.M. O'Brien, R.H. Fish.

Critical revision of the article for important intellectual content: J.M. O'Brien, C.H. Welsh, M. Ancukiewicz, A. Kramer.

Final approval of the article: J.M. O'Brien, C.H. Welsh, M. Ancukiewicz, A. Kramer.

Provision of study materials or patients: C.H. Welsh.

Statistical expertise: R.H. Fish, M. Ancukiewicz, A. Kramer.

Obtaining of funding: J.M. O'Brien.

Administrative, technical, or logistic support: J.M. O'Brien, C.H. Welsh, R.H. Fish, A. Kramer.

Collection and assembly of data: J.M. O'Brien, C.H. Welsh, R.H. Fish, M. Ancukiewicz.