So imagine this clinical situation…
You just came on shift in the emergency department. Your partner has just finished telling you about the COPD patient he had to intubate when the nurse for the patient comes rushing out and says “somethings wrong doctor, come quick!” Your partner quickly says “I’m out!”
You enter the room and find the “new” respiratory therapist at the bedside. He tells you that the patient is increasingly hard to ventilate and the plateau pressures are very high. What would be your immediate first step?
My immediate first step would be to disconnect the ventilator to allow the patient to have a nice long exhale! I would listen for any evidence of barotrauma. Following that, I would ask that respiratory therapist to increase the expiratory time, decrease the rate, and monitor plateau pressures very closely.
What has happened here is that the patient is experiencing “gas trapping” creating auto PEEP. Some people will just say the patient is “auto PEEP’ing.” Remember that in patients with COPD and asthma, one key issue is that the patient takes longer for exhalation. Intubating an asthmatic or COPD’er always gives me great stress and I do it ONLY as a last resort because of this problem. If you don’t allow for the increased expiratory time, the vent will deliver another breath before the last breath has been exhaled, thus increasing the pressure in the lung making it increasingly difficult to ventilate and greatly increasing the risk of barotrauma.
I’m linking to a great review article for this problem. The recommend as a starting point for vent settings for these patients:
Pressure control with tidal volume 6-8mL/kg
Rate 11-14 breaths per minute
Shortening inspiratory time/lengthening expiratory times
They recommend keeping the plateau pressures below 30 cm H2O