title: Risk factors for the development of nosocomial pneumonia and mortality on intensive care units: application of competing risks models.
abstract: BACKGROUND
  Pneumonia is a very common nosocomial infection in intensive care units (ICUs). Many studies have investigated risk factors for the development of infection and its consequences. However, the evaluation in most of theses studies disregards the fact that there are additional competing events, such as discharge or death.
  
  
  METHODS
  A prospective cohort study was conducted over 18 months in five intensive care units at one university hospital. All patients that were admitted for at least 2 days were included, and surveillance of nosocomial pneumonia was conducted. Various potential risk factors (baseline- and time-dependent) were evaluated in two competing risks models: the acquisition of nosocomial pneumonia and discharge (dead or alive; model 1) and for the risk of death in the ICU and discharge alive (model 2).
  
  
  RESULTS
  Patients from 1,876 admissions were included. A total of 158 patients developed nosocomial pneumonia. The main risk factors for nosocomial pneumonia in the multivariate analysis in model 1 were: elective surgery (cause-specific hazard ratio = 1.95; 95% CI 1.33 to 2.85) or emergency surgery (1.59; 95% CI 1.10 to 2.28) prior to ICU admission, usage of a nasogastric tube (3.04; 95% CI 1.25 to 7.37) and mechanical ventilation (5.90; 95% CI 2.47 to 14.09). Nosocomial pneumonia prolonged the length of ICU stay but was not directly associated with a fatal outcome (p = 0.55).
  
  
  CONCLUSIONS
  More studies using competing risk models, which provide more accurate data compared to naive survival curves or logistic models, should be carried out to verify the impact of risk factors and patient characteristics for the acquisition of nosocomial infections and infection-associated mortality.
authors.affiliation: Institute of Medical Biometry and Medical Informatics, University Medical Center Freiburg, Freiburg, Germany. wolke@fdm.uni-freiburg.de
authors.forename: Martin
authors.initials: M
authors.lastname: Wolkewitz
authors.forename: Ralf Peter
authors.initials: RP
authors.lastname: Vonberg
authors.forename: Hajo
authors.initials: H
authors.lastname: Grundmann
authors.forename: Jan
authors.initials: J
authors.lastname: Beyersmann
authors.forename: Petra
authors.initials: P
authors.lastname: Gastmeier
authors.forename: Sina
authors.initials: S
authors.lastname: Bärwolff
authors.forename: Christine
authors.initials: C
authors.lastname: Geffers
authors.forename: Michael
authors.initials: M
authors.lastname: Behnke
authors.forename: Henning
authors.initials: H
authors.lastname: Rüden
authors.forename: Martin
authors.initials: M
authors.lastname: Schumacher
mesh_terms: D003428:Cross Infection / Q000401:mortality*; D005260:Female; D006801:Humans; D007362:Intensive Care Units; D007442:Intubation, Intratracheal; D007902:Length of Stay / Q000706:statistics & numerical data; D008297:Male; D015233:Models, Statistical; D011014:Pneumonia / Q000401:mortality*; D011159:Population Surveillance; D016016:Proportional Hazards Models; D011446:Prospective Studies; D012121:Respiration, Artificial; D018570:Risk Assessment / Q000379:methods*; D012307:Risk Factors; D013514:Surgical Procedures, Operative