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Prolonged acute mechanical ventilation: implications for hospital benchmarking
Marya D Zilberberg1, Andrew A Kramer2, Thomas L Higgins3
1School of Public Health and Health Sciences, University of Massachusetts, Amherst, MA.
Background:
Hospital performance measures rely on aggregate outcomes. For patients receiving mechanical ventilation (MV), outcomes depend on severity of illness, hospital MV volume, and case mix. Patients requiring prolonged acute MV (PAMV) [MV for >or= 96 h] comprise a resource-intensive group, but the impact of its volume on aggregate outcomes is unknown. We investigated whether observed outcomes differed from those predicted by APACHE (acute physiology and chronic health evaluation) IV risk adjustment and the relationship between hospital MV volume and outcomes among patients receiving PAMV.
Methods:
We conducted a retrospective cohort study using the APACHE IV database between the years 2001 and 2005.
Results:
Of the 94,553 patients receiving MV at 45 hospitals, 24,366 (25.8%) were receiving PAMV. Unadjusted mortality was 32.3% for patients receiving PAMV and 22.9% for patients receiving short-term MV (STMV) [< 96 h]. Although mortality predictions were accurate in both groups, the length-of-stay (LOS) predictions underestimated duration of MV, ICU LOS, and hospital LOS by 5.2, 4.6, and 5.4 days, respectively, in the PAMV group. After stratifying the PAMV group by hospital MV volume, except for quintile 1, the standardized mortality ratio (SMR) was found to be inversely related to the volume quintile. The difference between actual and predicted MV durations, however, exhibited a consistent direct relationship with the MV volume.
Conclusions:
In patients requiring PAMV, the SMR is inversely proportional to hospital MV volume. Conversely, the PAMV group had a disproportionate effect on durations of MV, ICU LOS, and hospital LOS, and these marginal excesses increased with the hospital MV volume quintile. Development of specific predictive equations for patients receiving PAMV is recommended. Benchmarking measures must consider the case mix of patients receiving STMV vs those receiving PAMV.
Insights
Higher hospital mechanical ventilation (MV) volume is linked to lower mortality for prolonged acute MV (PAMV) patients. However, increased MV volume also correlates with longer hospital stays for these resource-intensive patients.
Area of Science:
- Critical Care Medicine
- Health Services Research
- Outcomes Research
Background:
- Hospital performance metrics often use aggregated outcomes, potentially masking variations in care for specific patient groups.
- Patients requiring prolonged acute mechanical ventilation (PAMV) are resource-intensive, but their outcomes relative to hospital volume are not well understood.
- Existing risk adjustment models may not fully capture the complexities of PAMV patient outcomes.
Purpose of the Study:
- To evaluate if observed outcomes for PAMV patients differed from APACHE IV predictions.
- To determine the relationship between hospital mechanical ventilation (MV) volume and outcomes in PAMV patients.
Main Methods:
- Retrospective cohort study utilizing the APACHE IV database (2001-2005).
- Analysis of 94,553 patients receiving MV across 45 hospitals, with a focus on the 25.8% receiving PAMV (>or= 96 hours).
- Stratification of PAMV patients by hospital MV volume quintiles to assess mortality and length-of-stay variations.
Main Results:
- While APACHE IV accurately predicted mortality, it underestimated length-of-stay (LOS) for PAMV patients by 4.6-5.4 days.
- Standardized mortality ratio (SMR) for PAMV patients showed an inverse relationship with hospital MV volume (higher volume, lower SMR), except in the lowest volume quintile.
- The discrepancy between actual and predicted MV durations increased proportionally with hospital MV volume.
Conclusions:
- Hospital MV volume is inversely related to mortality in PAMV patients.
- PAMV patients disproportionately impact and increase durations of MV, ICU LOS, and hospital LOS, with these excesses rising with hospital MV volume.
- Specific predictive models for PAMV patients and consideration of STMV vs. PAMV case mix are recommended for performance benchmarking.
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