OK, so we all know not to, "...Fall asleep on Auto-PEEP" thanks to Dr. Mallemat's pearl that can be seen here. But now the question is, how do you know if your patient is air-trapping?
There are 3 ways you can look for evidence of Auto-PEEP on the ventilator:
Do an end-expiratory hold: If the measured PEEP is more than the PEEP set on the vent after a 2-3 second hold, the difference is your Auto-PEEP.
Look at the expiratory flow waveform: If the waveform does not return to baseline (still expiring when inspiratory ventilation occurs), there's Auto-PEEP!
Compare the inspiratory vs. expiratory volumes. If the inspiratory volumes are much higher then the expiratory volumes, consider Auto-PEEP.
References
Blanch L, Bernabé F, Lucangelo U. Measurement of air trapping, intrinsic positive end-expiratory pressure, and dynamic hyperinflation in mechanically ventilated patients. Respir Care. 2005;50(1):110-23.
