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ICU Occupancy and Mechanical Ventilator Use in the United States*

Wunsch, Hannah MD, MSc1,2; Wagner, Jason MD3; Herlim, Maximilian4; Chong, David H. MD5; Kramer, Andrew A. PhD6; Halpern, Scott D. MD, PhD3,4,7,8

doi: 10.1097/CCM.0b013e318298a139
Clinical Investigations

Objectives: Detailed data on occupancy and use of mechanical ventilators in U. S. ICU over time and across unit types are lacking. We sought to describe the hourly bed occupancy and use of ventilators in U.S. ICUs to improve future planning of both the routine and disaster provision of intensive care.

Design: Retrospective cohort study. We calculated mean hourly bed occupancy in each ICU and hourly bed occupancy for patients on mechanical ventilators. We assessed trends in overall occupancy over the 3 years. We also assessed occupancy and mechanical ventilation rates across different types and sizes of ICUs.

Setting: Ninety-seven U.S. ICUs participating in Project IMPACT from 2005 to 2007.

Patients: A total of 226,942 consecutive admissions to ICUs.

Interventions: None.

Measurements and Main Results: Over the 3 years studied, total ICU occupancy ranged from 57.4% to 82.1% and the number of beds filled with mechanically ventilated patients ranged from 20.7% to 38.9%. There was no change in occupancy across years and no increase in occupancy during influenza seasons. Mean hourly occupancy across ICUs was 68.2% ± 21.3% (SD) and was substantially higher in ICUs with fewer beds (mean, 75.8% ± 16.5% for 5–14 beds vs 60.9% ± 22.1% for 20+ beds, p = 0.001) and in academic hospitals (78.7% ± 15.9% vs 65.3% ± 21.3% for community not-for-profit hospitals, p < 0.001). More than half of ICUs (53.6%) had 4+ beds available more than half the time. The mean percentage of ICU patients receiving mechanical ventilation in any given hour was 39.5% (± 15.2%), and a mean of 29.0% (± 15.9%) of ICU beds were filled with a patient on a ventilator.

Conclusions: Occupancy of U.S. ICUs was stable over time, but there is uneven distribution across different types and sizes of units. Only three of 10 beds were filled at any time with mechanically ventilated patients, suggesting substantial surge capacity throughout the system to care for acutely critically ill patients.

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1Department of Anesthesiology, Columbia University, New York, NY.

2Department of Epidemiology, Columbia University, New York, NY.

3Division of Pulmonary, Allergy, and Critical Care Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA.

4Department of Biostatistics & Epidemiology, Center for Clinical Epidemiology and Biostatistics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA.

5Department of Medicine, Columbia University, New York, NY.

6Cerner Corporation, Vienna, VA.

7Department of Medical Ethics and Health Policy, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA.

8Leonard Davis Institute of Health Economics, University of Pennsylvania, Philadelphia, PA.

* See also p. 2820.

Drs. Wunsch, Chong, Kramer, and Halpern conceived and designed the study. All authors analyzed and interpreted the data, drafted and critically revised the article for important intellectual content, and approved the article. Drs. Wunsch and Halpern were statistical expertise and obtained funding. Drs. Wunsch, Herlim, Kramer, and Halpern collected and assembled the data.

This work was done in the University of Pennsylvania, Columbia University, and Cerner Corporation.

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Supported, in part, by grant UL1 RR024156 from National Center for Research Resources and the National Center for Advancing Translational Sciences, NIH.

The funders had no role in the design and conduct of the study; collection, management, analysis, and interpretation of the data; preparation, review, or approval of the manuscript.

Dr. Wunsch was supported by K08AG038477 from the NIA/NIH, Dr. Wagner was supported by T32HL0980 from NHLBI/NIH, and Dr. Halpern was supported by K08HS018406 from AHRQ and a Society of Critical Care Medicine Vision Grant. The remaining authors have disclosed that they do not have any potential conflicts of interest.

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© 2013 by the Society of Critical Care Medicine and Lippincott Williams & Wilkins