title: Effect of different inspiratory rise time and cycling off criteria during pressure support ventilation in patients recovering from acute lung injury.
abstract: OBJECTIVE
  With many mechanical ventilators, it is possible to modify the time to reach the selected airway pressure and the criteria for cycling off the inflation during pressure support ventilation. This study evaluated the effect of different inspiratory rise time and cycling off criteria on breathing pattern and work of breathing.
  
  
  METHODS
  Clinical study.
  
  
  METHODS
  University laboratory.
  
  
  METHODS
  Ten intubated patients recovering from acute lung injury (PaO2/FiO2 245 +/- 26 torr, positive end-expiratory pressure 9 +/- 3 cm H2O).
  
  
  METHODS
  We studied two inspiratory rise time criteria (shortest and longest, 0% and 40% of the breath cycle time) and two cycling off criteria (lowest and highest, 5% and 40% of the peak inspiratory flow) at 5 and 15 cm H2O of pressure support. Respiratory rate, tidal volume, and inspiratory and expiratory work of breathing (WOBI and WOBE) were measured.
  
  
  RESULTS
  At both levels of pressure support ventilation, the shortest inspiratory rise time significantly reduced the WOBI from 0.77 +/- 0.32 to 0.56 +/- 0.23 J/L and from 0.24 +/- 0.28 to 0.08 +/- 0.09 J/L without affecting respiratory rate or tidal volume. At 15 cm H2O of pressure support ventilation, the lowest cycling off criteria significantly reduced respiratory rate from 24.9 +/- 12.1 to 21.5 +/- 12.7 beats/min and increased tidal volume from 0.51 +/- 0.17 to 0.60 +/- 0.26 L. At both levels of pressure support ventilation, the modification of cycling off criteria did not influence WOBI and WOBE.
  
  
  CONCLUSIONS
  Our results suggest that in patients recovering from acute lung injury during pressure support ventilation, a) the shortest inspiratory rise time reduces the WOBI; and b) at 15 cm H2O of pressure support ventilation, the lowest cycling off criteria reduces the respiratory rate and increases the tidal volume without modifying the WOBI and WOBE. Modifications of inspiratory rise time and cycling off criteria must be carefully adjusted during pressure support ventilation.
authors: Istituto di Anestesia e Reanimazione, Universita' degli Studi Milano, Ospedale Policlinico-IRCSS, Milan, Italy.
authors: Davide
authors: D
authors: Chiumello
authors: Paolo
authors: P
authors: Pelosi
authors: Paolo
authors: P
authors: Taccone
authors: Arthur
authors: A
authors: Slutsky
authors: Luciano
authors: L
authors: Gattinoni
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011175:Positive-Pressure Respiration / Q000379:methods*; D011659:Pulmonary Gas Exchange; D012128:Respiratory Distress Syndrome / Q000628:therapy*; D014939:Work of Breathing