Published in:
Open Access
01-12-2016 | Research
Accuracy of delivered airway pressure and work of breathing estimation during proportional assist ventilation: a bench study
Authors:
Francois Beloncle, Evangelia Akoumianaki, Nuttapol Rittayamai, Aissam Lyazidi, Laurent Brochard
Published in:
Annals of Intensive Care
|
Issue 1/2016
Login to get access
Abstract
Background
Proportional assist ventilation+ (PAV+) delivers airway pressure (P
aw) in proportion to patient effort (P
mus) by using the equation of motion of the respiratory system. PAV+ calculates automatically respiratory mechanics (elastance and resistance); the work of breathing (WOB) is estimated by the ventilator. The accuracy of P
mus estimation and hence accuracy of the delivered P
aw and WOB calculation have not been assessed. This study aimed at assessing the accuracy of delivered P
aw and calculated WOB by PAV+ and examining the factors influencing this accuracy.
Methods
Using an active lung model with different respiratory mechanics, we compared (1) the actual delivered P
aw by the ventilator to the theoretical P
aw as defined by the equation of motion and (2) the WOB value displayed by the ventilator to the WOB measured from a Campbell diagram.
Results
Irrespective of respiratory mechanics and gain, the ventilator provided a P
aw approximately 25 % lower than expected. This underassistance was greatest at the beginning of the inspiration. Intrinsic PEEP (PEEPi), associated with an increase in trigger delay, was a major factor affecting PAV+ accuracy. The absolute value of total WOB displayed by the ventilator was underestimated, but the changes in WOB were accurately detected by the ventilator.
Conclusion
The assistance provided by PAV+ well follows P
mus but with a constant underassistance. This is associated with an underestimation by the ventilator of the WOB. PEEPi can be a major factor contributing to PAV+ inaccuracy. Clinical recommendations should include using a high trigger sensitivity and a careful PEEP titration.