Expiratory trigger setting in pressure support ventilation: from mathematical model to bedside.
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.
Tassaux
Didier
D
Division of Medical Intensive Care, University Hospital, Geneva, Switzerland.
Michotte
Jean-Bernard
JB
Gainnier
Marc
M
Gratadour
Pierre
P
Fonseca
Silvana
S
Jolliet
Philippe
P
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