title: Replacement of anesthesia machines improves intraoperative ventilation parameters associated with the development of acute respiratory distress syndrome.
abstract: BACKGROUND
  The impact of anesthetic equipment on clinical practice parameters associated with development of acute respiratory distress syndrome (ARDS) has not been extensively studied. We hypothesized a change in anesthesia machines would be associated with parameters associated with lower rates of ARDS.
  
  
  METHODS
  We performed a retrospective cohort study on a subset of data used to evaluate intraoperative ventilation. Patients included adults receiving a non-cardiac, non-thoracic, non-transplant, non-trauma, general anesthetic between 2/1/05, and 3/31/09 at the University of Michigan. Existing anesthesia machines (Narkomed IIb, Drager) were exchanged for new equipment (Aisys, General Electric). The initial subset compared the characteristics of patients anesthetized between 12/1/06 and 1/31/07 (pre) with those between 4/1/07 and 5/30/07 (post). An extended subset examined cases two years pre and post exchange. Using the standard predicted body weight (PBW), we calculated and compared the tidal volume (total Vt and mL/kg PBW) as well as positive end-expiratory pressure (PEEP), peak inspiratory pressure (PIP), Delta P (PIP-PEEP), and FiO2.
  
  
  RESULTS
  A total of 1,414 patients were included in the 2-month pre group and 1,635 patients included in the post group. Comparison of ventilation characteristics found statistically significant differences in median (pre v post): PIP (26 ± 6 v 21 ± 6 cmH2O, p < .001), Delta P (24 ± 6 v 19 ± 6 cmH2O, p < .001), Vt (588 ± 139 v 562 ± 121 ml, p < 0.001; 9.3 ± 2.2 v 9.0 ± 1.9 ml/kg predicted body weight, p < .001), FiO2 (0.57 ± 0.17 v 0.52 ± 0.18, p < .001). Groups did not differ in age, ASA category, PBW, or BMI. The two year subgroup had similar parameters. Risk adjustment resulted in minimal differences in the analysis. New anesthesia machines were associated with a non-statistically significant reduction in postoperative ARDS.
  
  
  CONCLUSIONS
  In this study, a change in ventilator management was associated with an anesthesia machine exchange. The smaller Vt and lower PIP noted in the post group may imply a lower risk of volutrauma and barotrauma, which may be significant in at-risk populations. However, there was not a statistically significant reduction in the incidence of post-operative ARDS.
authors.affiliation: Department of Anesthesiology, Emory University School of Medicine, 1364 Clifton Road NE, Atlanta, GA 30322, USA ; Emory Critical Care Center, Woodruff Health Sciences Center Administration Building, 1440 Clifton Road NE, Suite 313, Atlanta, GA 30322, USA.
authors.forename: James M
authors.initials: JM
authors.lastname: Blum
authors.affiliation: Department of Anesthesiology, The Ohio State University, 410 W 10th Avenue, Columbus, OH 43210, USA.
authors.forename: Victor
authors.initials: V
authors.lastname: Davila
authors.affiliation: Department of Anesthesiology, Division of Critical Care, The University of Michigan Health System, 1500 East Medical Center Drive, Ann Arbor, MI 48109-5861, USA.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Stentz
authors.affiliation: Department of Respiratory Therapy, The University of Michigan Health Systems, 1500 East Medical Center Drive, Ann Arbor, MI 48109-5861, USA.
authors.forename: Ronald
authors.initials: R
authors.lastname: Dechert
authors.affiliation: Department of Anesthesiology, Division of Critical Care, The University of Michigan Health System, 1500 East Medical Center Drive, Ann Arbor, MI 48109-5861, USA.
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Jewell
authors.affiliation: Department of Anesthesiology, Division of Critical Care, The University of Michigan Health System, 1500 East Medical Center Drive, Ann Arbor, MI 48109-5861, USA.
authors.forename: Milo
authors.initials: M
authors.lastname: Engoren
mesh_terms: D000328:Adult; D000368:Aged; D000758:Anesthesia / Q000379:methods*; D000776:Anesthesiology / Q000295:instrumentation*; D001784:Blood Gas Analysis; D015331:Cohort Studies; D005260:Female; D006801:Humans; D007430:Intraoperative Care / Q000379:methods*; D008297:Male; D008838:Microcomputers; D008875:Middle Aged; D011446:Prospective Studies; D012121:Respiration, Artificial / Q000295:instrumentation*; D012128:Respiratory Distress Syndrome / Q000503:physiopathology / Q000628:therapy*; D012189:Retrospective Studies; D013990:Tidal Volume
keywords: ARDS; Equipment upgrade; Perioperative ventilation; Study design