title: Prolonged acute mechanical ventilation: implications for hospital benchmarking.
abstract: 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.
authors.affiliation: School of Public Health and Health Sciences, University of Massachusetts, Amherst, MA. Electronic address: Marya@EviMedGroup.org.
authors.forename: Marya D
authors.initials: MD
authors.lastname: Zilberberg
authors.affiliation: Cerner Corporation, Kansas City, MO.
authors.forename: Andrew A
authors.initials: AA
authors.lastname: Kramer
authors.affiliation: Division of Critical Care Medicine, Baystate Medical Center, Springfield, MA.
authors.forename: Thomas L
authors.initials: TL
authors.lastname: Higgins
authors.affiliation: Division of Pulmonary and Critical Care, Washington Hospital Center, Washington, DC.
authors.forename: Andrew F
authors.initials: AF
authors.lastname: Shorr
mesh_terms: D018806:APACHE; D000368:Aged; D019985:Benchmarking; D003953:Diagnosis-Related Groups; D005260:Female; D017052:Hospital Mortality; D006801:Humans; D007362:Intensive Care Units / Q000592:standards*; D007902:Length of Stay; D008297:Male; D008875:Middle Aged; D017063:Outcome Assessment, Health Care; D012121:Respiration, Artificial / Q000706:statistics & numerical data*; D012189:Retrospective Studies; D020379:Risk Adjustment; D012720:Severity of Illness Index; D013997:Time Factors; D014481:United States