title: Compared to conventional ventilation, airway pressure release  ventilation may increase ventilator days in trauma patients.
abstract: BACKGROUND
  Airway pressure release ventilation (APRV) is used both as a rescue therapy for patients with acute lung injury and as a primary mode of ventilation. Unlike assist-control volume (ACV) ventilation that uses spontaneous breathing trials, APRV weaning consists of gradual decreases in supporting pressure. We hypothesized that the APRV weaning process increases total ventilator days compared with those of spontaneous breathing trials-based weaning.
  
  
  METHODS
  A retrospective review of a Level I trauma center's database identified trauma admissions from January 1, 2007, to December 31, 2010, which required mechanical ventilation for more than 24 hours and survived. Demographics, injuries, in-hospital complications, ventilation mode(s), and total ventilator days were abstracted.
  
  
  RESULTS
  A total of 362 patients fulfilled study entry criteria; 53 patients with more than one ventilator mode change were excluded. Seventy-five patients were successfully liberated from mechanical ventilation on APRV and 234 on ACV. The APRV and ACV groups, respectively, were similar in age (46.1 vs. 44.6 years) and sex (72% vs. 73% male) but differed in Injury Severity Score (20.8 vs. 17.5; p = 0.03). Patients on APRV had higher rates of abdominal compartment syndrome (6.7% vs. 0.8%, p = 0.003) and were more likely to have a higher chest Abbreviated Injury Scale (AIS) score ≥3 (57.3% vs. 30.8%, p < 0.001). Ventilator days were significantly greater in the APRV group (19.6 vs. 10.7 days, p < 0.001). Multiple regression was performed to adjust for the clinical differences between the two groups, identifying APRV as an independent predictor for increased number of ventilator days (B = 6.2 ± 1.5, p < 0.001) in addition to male sex, abdomen AIS score of 3 or higher, spine AIS score of 3 or higher, acute renal failure, and sepsis.
  
  
  CONCLUSIONS
  APRV is frequently used for patients who are more severely injured or who develop in-hospital complications such as pneumonia. However, after controlling for potential confounding factors in a multiple regression model, the APRV mode itself seems to increase ventilator days.
authors.affiliation: Section of Trauma, Surgical Critical Care and Surgical Emergencies, Department of Surgery, School of Medicine, Yale University, New Haven, CT 06520, USA. adrian.maung@yale.edu
authors.forename: Adrian A
authors.initials: AA
authors.lastname: Maung
authors.forename: Kevin M
authors.initials: KM
authors.lastname: Schuster
authors.forename: Lewis J
authors.initials: LJ
authors.lastname: Kaplan
authors.forename: Michael F
authors.initials: MF
authors.lastname: Ditillo
authors.forename: Greta L
authors.initials: GL
authors.lastname: Piper
authors.forename: Linda L
authors.initials: LL
authors.lastname: Maerz
authors.forename: Felix Y
authors.initials: FY
authors.lastname: Lui
authors.forename: Dirk C
authors.initials: DC
authors.lastname: Johnson
authors.forename: Kimberly A
authors.initials: KA
authors.lastname: Davis
mesh_terms: D000328:Adult; D000368:Aged; D045422:Continuous Positive Airway Pressure / Q000009:adverse effects / Q000379:methods*; D003422:Critical Care / Q000379:methods; D016208:Databases, Factual; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D015601:Injury Severity Score; D059325:Intra-Abdominal Hypertension / Q000175:diagnosis / Q000453:epidemiology; D007902:Length of Stay; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D011659:Pulmonary Gas Exchange; D012121:Respiration, Artificial / Q000379:methods*; D012189:Retrospective Studies; D018570:Risk Assessment; D015996:Survival Rate; D013997:Time Factors; D014193:Trauma Centers; D016896:Treatment Outcome; D015300:Ventilator Weaning; D014947:Wounds and Injuries / Q000175:diagnosis / Q000401:mortality / Q000628:therapy*