title: Comparative effects of proportional assist and variable pressure support ventilation on lung function and damage in experimental lung injury.
abstract: OBJECTIVE
  To investigate the effects of proportional assist ventilation, variable pressure support, and conventional pressure support ventilation on lung function and damage in experimental acute lung injury.
  
  
  METHODS
  : Randomized experimental study.
  
  
  METHODS
  University hospital research facility.
  
  
  METHODS
  : Twenty-four juvenile pigs.
  
  
  METHODS
  Pigs were anesthetized, intubated, and mechanically ventilated. Acute lung injury was induced by saline lung lavage. After resuming of spontaneous breathing, animals were randomly assigned to 6 hrs of assisted ventilation with pressure support ventilation, proportional assist ventilation, or variable pressure support (n = 8 per group). Mean tidal volume was kept at ≈6 mL/kg in all modes.
  
  
  RESULTS
  Lung functional parameters, distribution of ventilation by electrical impedance tomography, and breathing patterns were analyzed. Histological lung damage and pulmonary inflammatory response were determined postmortem. Variable -pressure support and proportional assist ventilation improved oxygenation and venous admixture compared with pressure support ventilation. Proportional assist ventilation led to higher esophageal pressure time product than variable pressure support and pressure support ventilation, and redistributed ventilation from central to dorsal lung regions compared to pressure support ventilation. Variable pressure support and proportional assist ventilation yielded higher tidal volume variability than pressure support ventilation. Such pattern was deterministic (self-organized) during proportional assist ventilation and stochastic (random) during variable pressure support. Subject-ventilator synchrony as well as pulmonary inflammatory response and damage did not differ among groups.
  
  
  CONCLUSIONS
  In a lung lavage model of acute lung injury, both variable pressure support and proportional assist ventilation increased the variability of tidal volume and improved oxygenation and venous admixture, without influencing subject-ventilator synchrony or affecting lung injury compared with pressure support ventilation. However, variable pressure support yielded less inspiratory effort than proportional assist ventilation at comparable mean tidal volumes of 6 mL/kg.
authors: Pulmonary Engineering Group, Department of Anesthesiology and Intensive Care Therapy, University Hospital, Dresden, Germany.
authors: Peter M
authors: PM
authors: Spieth
authors: Andreas
authors: A
authors: Güldner
authors: Alessandro
authors: A
authors: Beda
authors: Nadja
authors: N
authors: Carvalho
authors: Thomas
authors: T
authors: Nowack
authors: Anke
authors: A
authors: Krause
authors: Ines
authors: I
authors: Rentzsch
authors: Sabina
authors: S
authors: Suchantke
authors: Serge C
authors: SC
authors: Thal
authors: Kristin
authors: K
authors: Engelhard
authors: Michael
authors: M
authors: Kasper
authors: Thea
authors: T
authors: Koch
authors: Paolo
authors: P
authors: Pelosi
authors: Marcelo Gama
authors: MG
authors: de Abreu
mesh_terms: D055371:Acute Lung Injury / Q000401:mortality / Q000473:pathology / Q000628:therapy*; D000818:Animals; D004195:Disease Models, Animal; D006439:Hemodynamics / Q000502:physiology; D018836:Inflammation Mediators / Q000378:metabolism; D059725:Interactive Ventilatory Support / Q000009:adverse effects / Q000379:methods*; D011175:Positive-Pressure Respiration / Q000009:adverse effects / Q000379:methods*; D011659:Pulmonary Gas Exchange; D012333:RNA, Messenger / Q000032:analysis; D011897:Random Allocation; D012129:Respiratory Function Tests; D018570:Risk Assessment; D012680:Sensitivity and Specificity; D013552:Swine; D016896:Treatment Outcome; D055397:Ventilator-Induced Lung Injury / Q000473:pathology* / Q000503:physiopathology
chemical_list: D018836:Inflammation Mediators; D012333:RNA, Messenger