title: Short-term cardiorespiratory effects of proportional assist and pressure-support ventilation in patients with acute lung injury/acute respiratory distress syndrome.
abstract: BACKGROUND
  Recent data indicate that assisted modes of mechanical ventilation improve pulmonary gas exchange in patients with acute lung injury (ALI)/acute respiratory distress syndrome (ARDS). Proportional assist ventilation (PAV) is a new mode of support that amplifies the ventilatory output of the patient effort and improves patient-ventilator synchrony. It is not known whether this mode may be used in patients with ALI/ARDS. The aim of this study was to compare the effects of PAV and pressure-support ventilation on breathing pattern, hemodynamics, and gas exchange in a homogenous group of patients with ALI/ARDS due to sepsis.
  
  
  METHODS
  Twelve mechanically ventilated patients with ALI/ARDS (mean ratio of partial pressure of arterial oxygen to fractional concentration of oxygen 190 +/- 49 mmHg) were prospectively studied. Patients received pressure-support ventilation and PAV in random order for 30 min while maintaining mean airway pressure constant. With both modes, the level of applied positive end-expiratory pressure (7.1 +/- 2.1 cm H2O) was kept unchanged throughout. At the end of each study period, cardiorespiratory data were obtained, and dead space to tidal volume ratio was measured.
  
  
  RESULTS
  With both modes, none of the patients exhibited clinical signs of distress. With PAV, breathing frequency and cardiac index were slightly but significantly higher than the corresponding values with pressure-support ventilation (24.5 +/- 6.9 vs. 21.4 +/- 6.9 breaths/min and 4.4 +/- 1.6 vs. 4.1 +/- 1.3 l . min . m, respectively). None of the other parameters differ significantly between modes.
  
  
  CONCLUSIONS
  In patients with ALI/ARDS due to sepsis, PAV and pressure-support ventilation both have clinically comparable short-term effects on gas exchange and hemodynamics.
authors.affiliation: Intensive Care Medicine Department, University Hospital of Heraklion 71110, University of Crete, Heraklion, Crete, Greece. konde@med.uoc.gr
authors.forename: Eumorfia
authors.initials: E
authors.lastname: Kondili
authors.forename: Nectaria
authors.initials: N
authors.lastname: Xirouchaki
authors.forename: Katerina
authors.initials: K
authors.lastname: Vaporidi
authors.forename: Maria
authors.initials: M
authors.lastname: Klimathianaki
authors.forename: Dimitris
authors.initials: D
authors.lastname: Georgopoulos
mesh_terms: D000208:Acute Disease; D000328:Adult; D000368:Aged; D001784:Blood Gas Analysis; D003627:Data Interpretation, Statistical; D005260:Female; D006439:Hemodynamics / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D010100:Oxygen / Q000097:blood; D011175:Positive-Pressure Respiration; D011446:Prospective Studies; D011659:Pulmonary Gas Exchange; D012121:Respiration, Artificial; D012128:Respiratory Distress Syndrome / Q000503:physiopathology*; D015656:Respiratory Mechanics / Q000502:physiology*
chemical_list: D010100:Oxygen