This is an actual patient case:
65 y/o pt intubated for hemoptysis and started on nebulized transexamic acid. Overnight, the pt is found to have severe breath stacking/auto-PEEPing and consequently is started on neuromuscular blockade. The pt has no history of asthma or COPD and the ETT is clear without obstruction.
Ventilator waveforms are as shown. What is the issue?
Explanation:
On expiration, the ventilator pressure (and the pressure curve waveform on the ventilator) should drop to the set PEEP (10 cm H2O in this case) immediately. This is true regardless of whether it is volume control, pressure control, PRVC etc. For this patient, the pressure curve is not dropping to the set PEEP immediately on expiration, rather, it slowly decays and does not even reach the set PEEP before the beginning of the next breath. This is not due to a patient issue, but rather an obstruction at the level of the ventilator. In particular, an obstruction in the expiratory limb of the tubing where flow returns to the ventilator from the patient. TXA is known to crystallize on the expiratory filter which can cause this type of obstruction if it is not changed frequently enough, preventing the pressure from dropping to PEEP and the patient from fully exhaling.
In this case, the obstruction was localized to the expiratory filter based on the ventilator waveforms and the filter was exchanged. The waveforms normalized, the patient had no obstruction or breath stacking, the neuromuscular blockade discontinued, and the patient was subsequently extubated without issue.
