Presented by Dr Arthur MC KWAN at the daily Journal Club of ICU, PYNEH, Hong Kong, on 14 May 2009
In a retrospective cohort study using the APACHE IV database between the years 2001 and 2005 in 94,553 patients receiving MV at 45 US hospitals, 24,366 (25.8%) were receiving prolonged acute mechanical ventilation (PAMV, defined as MV for ≥ 96 h). Which of the following statement is wrong about the findings of this study?
A. The hospital mortality rate for the PAMV group was 70%
B. In patients requiring PAMV, the SMR was inversely proportional to hospital MV volume.
C. Patients receiving PAMV in hospitals with higher annual MV volumes were likely to have a longer LOS than those in the lower MV volume institutions.
D. The most frequent diagnostic groups in the PAMV group were: bacterial pneumonia, respiratory (other), cardiac arrest, COPD, and sepsis (pulmonary source)
Answer: A
The correct hospital mortality rate for the PAMV group is 32%
Editor’s Impression
The scenario in Hong Kong is different from US, therefore it would be useful and interesting if similar data can be obtained in Hong Kong, e.g. in the next APACHE project led by the Hospital Authority.
Reference
Marya D. Zilberberg, MD, MPH, FCCP*, Andrew A. Kramer, PhD, Thomas L. Higgins, MD, MBA and Andrew F. Shorr, MD, MPH, FCCP. Prolonged Acute Mechanical Ventilation: Implications for Hospital Benchmarking. CHEST May 2009 vol. 135 no. 5 1157-1162. *From the School of Public Health and Health Sciences (Dr. Zilberberg), University of Massachusetts, Amherst, MA; Cerner Corporation (Dr. Kramer), Kansas City, MO; the Division of Critical Care Medicine (Dr. Higgins), Baystate Medical Center, Springfield, MA; and the Division of Pulmonary and Critical Care (Dr. Shorr), Washington Hospital Center, Washington, DC. Abstract here.
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 ≥ 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.