title: Lung protective ventilation (ARDSNet) versus airway pressure release ventilation: ventilatory management in a combined model of acute lung and brain injury.
abstract: BACKGROUND
  Concomitant lung/brain traumatic injury results in significant morbidity and mortality. Lung protective ventilation (Acute Respiratory Distress Syndrome Network [ARDSNet]) has become the standard for managing adult respiratory distress syndrome; however, the resulting permissive hypercapnea may compound traumatic brain injury. Airway pressure release ventilation (APRV) offers an alternative strategy for the management of this patient population. APRV was hypothesized to retard the progression of acute lung/brain injury to a degree greater than ARDSNet in a swine model.
  
  
  METHODS
  Yorkshire swine were randomized to ARDSNet, APRV, or sham. Ventilatory settings and pulmonary parameters, vitals, blood gases, quantitative histopathology, and cerebral microdialysis were compared between groups using χ2, Fisher's exact, Student's t test, Wilcoxon rank-sum, and mixed-effects repeated-measures modeling.
  
  
  RESULTS
  Twenty-two swine (17 male, 5 female), weighing a mean (SD) of 25 (6.0) kg, were randomized to APRV (n = 9), ARDSNet (n = 12), or sham (n = 1). PaO2/FIO2 ratio dropped significantly, while intracranial pressure increased significantly for all three groups immediately following lung and brain injury. Over time, peak inspiratory pressure, mean airway pressure, and PaO2/FIO2 ratio significantly increased, while total respiratory rate significantly decreased within the APRV group compared with the ARDSNet group. Histopathology did not show significant differences between groups in overall brain or lung tissue injury; however, cerebral microdialysis trends suggested increased ischemia within the APRV group compared with ARDSNet over time.
  
  
  CONCLUSIONS
  Previous studies have not evaluated the effects of APRV in this population. While our macroscopic parameters and histopathology did not observe a significant difference between groups, microdialysis data suggest a trend toward increased cerebral ischemia associated with APRV over time. Additional and future studies should focus on extending the time interval for observation to further delineate differences between groups.
authors.affiliation: From the Department of Surgery (S.W.D., R.G.S), University of Virginia, School of Medicine, Charlottesville, Virginia; Division of Trauma and Acute Care Surgery (K.L.L., N.R.P., B.H.W., E.A.T.), Department of Surgery, Department of Pathology (R.K.F., R.P.M.), Department of Physiology (R.C.H.), Biostatistics Unit (J.T.E.), Center for Health Disparities, and Division of Neurosurgery (H.A.K.), The Brody School of Medicine, East Carolina University; and Vidant Medical Center (J.P.H., W.E.T.), Greenville, North Carolina.
authors.forename: Stephen W
authors.initials: SW
authors.lastname: Davies
authors.forename: Kenji L
authors.initials: KL
authors.lastname: Leonard
authors.forename: Randall K
authors.initials: RK
authors.lastname: Falls
authors.forename: Ronald P
authors.initials: RP
authors.lastname: Mageau
authors.forename: Jimmy T
authors.initials: JT
authors.lastname: Efird
authors.forename: Joseph P
authors.initials: JP
authors.lastname: Hollowell
authors.forename: Wayne E
authors.initials: WE
authors.lastname: Trainor
authors.forename: Hilal A
authors.initials: HA
authors.lastname: Kanaan
authors.forename: Robert C
authors.initials: RC
authors.lastname: Hickner
authors.forename: Robert G
authors.initials: RG
authors.lastname: Sawyer
authors.forename: Nathaniel R
authors.initials: NR
authors.lastname: Poulin
authors.forename: Brett H
authors.initials: BH
authors.lastname: Waibel
authors.forename: Eric A
authors.initials: EA
authors.lastname: Toschlog
mesh_terms: D055371:Acute Lung Injury / Q000150:complications / Q000473:pathology / Q000503:physiopathology / Q000517:prevention & control*; D000818:Animals; D001930:Brain Injuries / Q000150:complications / Q000473:pathology / Q000503:physiopathology / Q000517:prevention & control*; D045422:Continuous Positive Airway Pressure / Q000379:methods*; D006439:Hemodynamics / Q000502:physiology; D008170:Lung Compliance / Q000502:physiology; D017551:Microdialysis; D010865:Pilot Projects; D011897:Random Allocation; D012129:Respiratory Function Tests; D013552:Swine