Clinical study
Obesity-Associated hypoventilation in hospitalized patients: prevalence, effects, and outcome

https://doi.org/10.1016/j.amjmed.2003.08.022Get rights and content

Abstract

Background

Severe obesity is associated with hypoventilation, a disorder that may adversely affect morbidity and mortality. We sought to determine the prevalence and effects of obesity-associated hypoventilation in hospitalized patients.

Methods

Consecutive admissions to internal medicine services were screened over a 6-month period. In all eligible subjects with severe obesity (body mass index ≥35 kg/m2), we administered a sleep questionnaire, and performed neuropsychological, arterial blood gas, and pulmonary function testing. Hospital course and mortality at 18 months was also determined.

Results

Of 4332 admissions, 6% (n = 277) of patients were severely obese, of whom 150 were enrolled, 75 refused to participate, and 52 met the exclusion criteria. Hypoventilation (mean [± SD] arterial partial pressure of carbon dioxide [PaCO2], 52 ± 7 mm Hg) was present in 31% (n = 47) of subjects who did not have other reasons for hypercapnia. Decreased objective attention/concentration and increased subjective sleepiness were present in patients with obesity-associated hypoventilation compared with in severely obese hospitalized patients without hypoventilation (simple obesity group; mean PaCO2, 37 ± 6 mm Hg). There were higher rates of intensive care (P = 0.08), long-term care at discharge (P = 0.01), and mechanical ventilation (P = 0.01) among subjects with obesity-associated hypoventilation. Therapy for hypoventilation at discharge was initiated in only 6 (13%) of the patients with obesity-associated hypoventilation. At 18 months following hospital discharge, mortality was 23% in the obesity-associated hypoventilation group as compared with 9% in the simple obesity group (hazard ratio = 4.0; 95% confidence interval: 1.5 to 10.4].

Conclusion

Hypoventilation frequently complicates severe obesity among hospitalized adults and is associated with excess morbidity and mortality.

Section snippets

Study sample

We evaluated consecutive adults older than 18 years of age with a body mass index ≥35 kg/m2, who were admitted to medical services of three teaching hospitals (the Denver Veterans Affairs Medical Center, Denver Health Medical Center, and University of Colorado Hospital). The criterion for body mass index was based on initial pilot data gathered over a 1-month period and literature review suggesting that most previously reported obesity-associated hypoventilation subjects have a body mass index

Results

Of 4332 consecutive admissions, 277 subjects (6%) had a body mass index ≥35 kg/m2. Among these severely obese inpatients, 127 were excluded: 10 had an FEV1/FVC ≤50% or prior lung resection, 10 could not give informed consent, 32 used opiates, and 75 refused to participate because they were unwilling to undergo arterial puncture. The remaining 150 were enrolled.

Of the 150 patients, 47 (31%) met the criteria for obesity-associated hypoventilation, whereas the remaining 103 had simple obesity. As

Discussion

In the present study, 6% of patients hospitalized on medical services of three teaching hospitals were severely obese (body mass index ≥35 kg/ m2) and 31% (1% of all screened admissions) had hypercapnia unexplained by other disorders. These patients more often required intensive care and invasive mechanical ventilation, and had a significantly greater likelihood of discharge to long-term care facilities. Most notably, mortality at 18 months following discharge was 23%, which was nearly twice

Acknowledgements

We are indebted to Jaclyn Martinez for help in preparing the manuscript; Douglas Robertson, Anna Baron, PhD, and Judy Maselli, MSPH, for assistance in data analysis; to John Weil, William Kaehny, Robert Anderson, and John Steiner for their critical review of the manuscript; and to Robert W. Schrier for his financial and intellectual support.

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  • Cited by (0)

    Funding was provided by the Department of Medicine, University of Colorado Health Sciences Center, Denver, Colorado.

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