title: Effects of partial ventilatory support modalities on respiratory function in severe hypoxemic lung injury.
abstract: OBJECTIVE
  The early phase of acute respiratory distress syndrome (ARDS) is characterized by impaired respiratory mechanics, ventilation-perfusion mismatch, and severe hypoxemia. Partial ventilatory support can effectively unload the respiratory workload and improve pulmonary gas exchange with less hemodynamic compromise. The partial ventilatory support mode most indicated in early phases of ARDS has not been determined. This study compares the effects of assisted ventilatory techniques on breathing pattern, gas exchange, hemodynamic function, and respiratory effort with those of controlled mechanical ventilation in similarly sedated subjects.
  
  
  METHODS
  Prospectively randomized crossover animal study.
  
  
  METHODS
  Animal research laboratory.
  
  
  METHODS
  Eleven anesthetized and mechanically ventilated pigs.
  
  
  METHODS
  Acute lung injury was induced by lung lavage. Pressure-controlled ventilation (PCV), pressure-controlled assisted ventilation (P-ACV), bilevel positive airway pressure (BIPAP), and pressure support ventilation (PSV) with equal airway pressures and sedation were applied in random order.
  
  
  RESULTS
  Gas exchange, respiratory effort, and hemodynamic function were measured, and ventilation-perfusion distributions were calculated by multiple inert-gas-elimination techniques. The results revealed that partial ventilatory support was superior to PCV in maintaining adequate oxygenation and hemodynamic function with reduced sedation. The effects of P-ACV, BIPAP, and PSV were comparable with respect to gas exchange and hemodynamic function, except for a more pronounced reduction in shunt during BIPAP. P-ACV and PSV were superior to BIPAP to reduce respiratory drive and work of breathing. PSV affected the pattern of breathing and deadspace to a greater degree than did P-ACV.
  
  
  CONCLUSIONS
  In acute lung injury, P-ACV preserves oxygenation and hemodynamic function with less respiratory effort compared with BIPAP and reduces the need for sedation compared with PCV.
authors.affiliation: Department of Anesthesiology, Aachen University Hospital, Germany. mail@d-henzler.de
authors.forename: Dietrich
authors.initials: D
authors.lastname: Henzler
authors.forename: Paolo
authors.initials: P
authors.lastname: Pelosi
authors.forename: Ralf
authors.initials: R
authors.lastname: Bensberg
authors.forename: Rolf
authors.initials: R
authors.lastname: Dembinski
authors.forename: Michael
authors.initials: M
authors.lastname: Quintel
authors.forename: Veronica
authors.initials: V
authors.lastname: Pielen
authors.forename: Rolf
authors.initials: R
authors.lastname: Rossaint
authors.forename: Ralf
authors.initials: R
authors.lastname: Kuhlen
mesh_terms: D000818:Animals; D004195:Disease Models, Animal; D000860:Hypoxia / Q000150:complications*; D011175:Positive-Pressure Respiration / Q000379:methods*; D011446:Prospective Studies; D011659:Pulmonary Gas Exchange / Q000502:physiology*; D011669:Pulmonary Wedge Pressure / Q000502:physiology; D011897:Random Allocation; D012128:Respiratory Distress Syndrome / Q000209:etiology / Q000503:physiopathology* / Q000628:therapy*; D015656:Respiratory Mechanics / Q000502:physiology*; D013552:Swine; D016896:Treatment Outcome