Monday, August 22, 2016

Ventilators II


A patient with severe COPD presents with an acute exacerbation. He is intubated for hypercapneic respiratory failure and has the waveform seen above. Over the next hour, he develops significant hemodynamic instability. Suddenly, he has a cardiac arrest, and you immediately start CPR and follow ACLS.

Challenge: What is your next intervention (with the ventilator)?

Image shown under Fair Use.

4 comments:

RaH said...

this seems to be a case of Air trapping with a compression of the venous return... the intrathoracic pressure should be diminished (change the PEEP, if PEEP is high lower it, if PEED is 0 increasing it could help)

Anonymous said...

Not sure, but is this similar to auto PEEP? would you decrease the positive pressure support and/or PEEP and slightly increase time for expiration? Looks like the patient has not fully expired prior to the start of the subsequent inspiratory assist.

Craig Chen said...

great job!! this is air trapping / autoPEEP. You are both correct in that there isn't full exhalation before the next breath and the intrathoracic pressure is decreasing venous return. If there is time, you can adjust the vent settings to increase expiratory time. If there is severe hemodynamic compromise, disconnecting the vent will allow complete exhalation. It is true that adjusting the PEEP can help with cases of autoPEEP by decreasing the work required to trigger the ventilator, and this is called matching extrinsic PEEP to autoPEEP. Usually you would measure intrinsic PEEP and set the ventilator PEEP to be slightly under that.
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Ventilators II

The physiology shown has multiple names: intrinsic PEEP, autoPEEP, and dynamic hyperinflation. The flow waveform on expiration does not return to baseline, signifying that there is air trapping; the next breath starts before complete exhalation. As air trapping increases, end expiratory positive pressure builds (intrinsic or autoPEEP) which decreases preload. The immediate treatment is to disconnect the ventilator from the patient to allow full exhalation. Other interventions include decreasing minute ventilation and prolonging the expiration time.

Source: medschool.lsuhsc.edu.

Anonymous said...

Great, thank you!