Acute lung injury patients one-third less likely to die in 'closed' model ICUs

Patients with acute lung injury (ALI) are nearly one-third less likely to die if they are treated at ICUs that require board-certified critical care physicians to oversee patient care, as compared to patients treated at ICUs that allow any attending physician to oversee admission and case management.

ALI is an inflammatory disorder of the lung often seen in patients with pneumonia or sepsis. Mortality rates are high -- about 40 percent -- and worsen with age and co-morbidities. Treatment generally involves addressing the underlying condition and providing protective low tidal volume mechanical ventilation and supportive therapy.

“ICUs that require patient transfer to an intensivist run team or mandate a co-attending intensivist are associated with reduced mortality in patients with ALI,” wrote Miriam Treggiari, M.D., M.P.H., of the Harborview Medical Center at the University of Washington, who led the study that appears in the first issue for October of the American Journal of Respiratory and Critical Care Medicine, published by the American Thoracic Society.

The study is the first to use data from a population-based prospective cohort of patients to evaluate outcomes of different ICU organizational models. As part of the National Institutes of Health funded King County Lung Injury Project, all patients in Seattle area ICUs receiving mechanical ventilation were screened for ALI, between April 1999 and July 2000. Detailed data on co-morbidities, length of hospital stay and discharge information was collected. Questionnaires were sent to both the medical directors and/or attending physicians of the ICUs and the nurse managers to assess the organizational model and structure of the ICUs. The final study group included 1,075 patients in 22 ICUs across 16 hospitals.

Two-thirds of the patients were treated at “closed” ICUs—units that require cases to be managed by board-certified critical care physicians or that mandate intensivists to co-manage on all patients. The remaining third received care at “open” ICUs, where cases could be managed by any attending physicians with admitting privileges, and pulmonary consultations were optional. According to the American College of Chest Physicians, only 25 percent of ICUs nationwide follow the closed model.

There were no significant differences in the degree of illness between patients who were cared for in closed versus open ICUs as measured by Acute Physiological and Chronic Health Evaluation III (APACHE III) scores, but patients at closed ICUs were younger and more likely to be male.

“Patients cared for in a closed ICU had statistically significantly lower mortality than patients cared for in open ICUs,” the researchers reported. Interestingly, the effect remained significant after adjusting for a number of variables in the analysis. While 77 percent of patients in closed ICUs were seen by a pulmonary consultant, consults alone did not have a significant effect on mortality. Similarly, adjusting for nurse-to-patient ratio and hospital volume of mechanically ventilated patients had no effect on mortality. Of patients treated in open ICUs, 45 percent died; in closed ICUs there was 35 percent mortality.

The investigators noted that because of the small sample size of hospitals and the date of the data collection, it would be difficult to extrapolate their results to a general trend among ICUs in the United States. Noting that the use of low tidal volume mechanical ventilation differed between closed and open ICUs, the researchers remarked that other unrecognized differences in patient care could exist, but that their results add support for the positive effect of a closed ICU model on patient outcome.

“These findings add to the evidence of the important role of intensivist staffing in caring for critically ill patients, and support the recommendations to implement closed-model ICUs in the United States,” said Dr. Treggiari. “Further studies will need to investigate if the beneficial effects of closed ICU derive from higher degree of staffing that could facilitate earlier recognition of critical/deteriorating conditions or greater expertise in the specific management aspects of critical care patients.”