title: Expiratory trigger setting in pressure support ventilation: from mathematical model to bedside.
abstract: OBJECTIVE
  To evaluate the feasibility of relying on a mathematical model to adjust the optimal level of expiratory trigger, materialized by the ratio of inspiratory flow at the end of inspiratory effort (V'ti) and peak inspiratory flow (V'peak), or V'ti/V'peak, during pressure support, by comparing its predicted values with those measured in intubated patients.
  
  
  METHODS
  Prospective observational study.
  
  
  METHODS
  Medical intensive care unit, university hospital.
  
  
  METHODS
  There were 28 intubated patients undergoing pressure support.
  
  
  METHODS
  Pressure support as set by the clinician in charge.
  
  
  RESULTS
  A significant correlation was found between predicted and measured V'ti/V'peak ratios (r =.70; p <.001; mean +/- sd difference, -0.025 +/- 0.07; 95% confidence interval, -0.161 to 0.111). Overall, delayed cycling occurred in obstructive conditions, the delay increasing as obstructive disease was more severe.
  
  
  CONCLUSIONS
  A significant correlation was observed between predicted values of V'ti/V'peak and those values measured in patients undergoing pressure support. These findings should stimulate further research into the possible applications of this mathematical model to optimize expiratory trigger setting. Furthermore, our findings suggest that expiratory trigger should be adjustable and provide a wider range of cutoff levels than that which is currently available.
authors.affiliation: Division of Medical Intensive Care, University Hospital, Geneva, Switzerland.
authors.forename: Didier
authors.initials: D
authors.lastname: Tassaux
authors.forename: Jean-Bernard
authors.initials: JB
authors.lastname: Michotte
authors.forename: Marc
authors.initials: M
authors.lastname: Gainnier
authors.forename: Pierre
authors.initials: P
authors.lastname: Gratadour
authors.forename: Silvana
authors.initials: S
authors.lastname: Fonseca
authors.forename: Philippe
authors.initials: P
authors.lastname: Jolliet
mesh_terms: D005240:Feasibility Studies; D006801:Humans; D008875:Middle Aged; D008954:Models, Biological; D011175:Positive-Pressure Respiration / Q000379:methods*; D011237:Predictive Value of Tests; D011446:Prospective Studies; D015656:Respiratory Mechanics / Q000502:physiology*; D018709:Statistics, Nonparametric; D013990:Tidal Volume