title: Demand-flow airway pressure release ventilation as a partial ventilatory support mode: comparison with synchronized intermittent mandatory ventilation and pressure support ventilation.
abstract: OBJECTIVE
  To evaluate airway pressure release ventilation as a partial ventilatory support mode by comparing a demand-flow airway pressure release ventilation system with synchronized intermittent mandatory ventilation and pressure support ventilation.
  
  
  METHODS
  Prospective, nonrandomized, cross-over trial.
  
  
  METHODS
  Medical intensive care unit in a university medical center.
  
  
  METHODS
  Sixteen consecutive patients without chronic obstructive pulmonary disease with mechanical ventilatory support of 25% to 75% of total minute ventilation on synchronized intermittent mandatory ventilation, or 25% to 75% of maximal pressure support level on pressure support ventilation.
  
  
  METHODS
  Each mode of mechanical ventilation was supplied to patients with comparable levels of partial support for 30 mins.
  
  
  RESULTS
  Among three different modes, demand-flow airway pressure release ventilation achieved the lowest peak airway pressure (airway pressure release ventilation 9.1 +/- 2.6 cm H2O; pressure support ventilation 18.4 +/- 4.6 cm H2O; synchronized intermittent mandatory ventilation 34.8 +/- 7.7 cm H2O; p < .001). Hemodynamic status and oxygenation status were similar among these three modes. Five (31%) of the 16 patients felt that demand-flow airway pressure release ventilation was a less comfortable mode than synchronized intermittent mandatory ventilation or pressure support ventilation. This finding had no clear correlation with their duration of airway pressure release, preset machine deflation rate, or inspiratory/expiratory ratio of machine breath. Gross asynchrony of effort and ventilator cycling was noticed in two (13%) patients while they were receiving demand-flow airway pressure release ventilation.
  
  
  CONCLUSIONS
  We conclude that for patients who do not have chronic obstructive pulmonary disease, demand-flow airway pressure release ventilation can provide effective partial ventilatory support with lower peak airway pressure when compared with pressure support ventilation and synchronized intermittent mandatory ventilation. However, this airway pressure release ventilation system may be less comfortable than the other two modes, and asynchrony may occur in some patients.
authors.affiliation: Department of Medicine, Duke University Medical Center, Durham, NC 27710.
authors.forename: A A
authors.initials: AA
authors.lastname: Chiang
authors.forename: A
authors.initials: A
authors.lastname: Steinfeld
authors.forename: C
authors.initials: C
authors.lastname: Gropper
authors.forename: N
authors.initials: N
authors.lastname: MacIntyre
mesh_terms: D000704:Analysis of Variance; D002319:Cardiovascular System / Q000503:physiopathology; D003422:Critical Care; D016638:Critical Illness; D006801:Humans; D007384:Intermittent Positive-Pressure Breathing; D007385:Intermittent Positive-Pressure Ventilation; D011446:Prospective Studies; D011659:Pulmonary Gas Exchange / Q000502:physiology