A patient is intubated due to an acute exacerbation of COPD. The patient is now breathing with pressure support ventilation 5 cm H2O and CPAP 5 cm H2O. The patient is unable to flow trigger every inspiration. Unintended positive end-expiratory pressure (auto-PEEP) is measured at 10 cm H2O. The most appropriate action to take is which of the following?

• A. Increase the CPAP to 8 cm H2O
• B. Increase the pressure support to 10 cm H2O
• C. Switch to a lower CPAP
• D. Increase the trigger sensitivity

Answer: (A)

Auto-PEEP in COPD creates a backpressure at the end of expiration, so the patient must overcome a higher baseline pressure to start a new breath. In flow-triggered ventilation, this makes triggering harder and increases the work of breathing. The way to improve triggering in this situation is to raise the external PEEP (CPAP) to offset the auto-PEEP. By increasing CPAP from 5 to 8 cm H2O, you raise the baseline airway pressure closer to the auto-PEEP level, reducing the pressure and flow the patient must overcome to trigger the ventilator, which helps with the flow-trigger issue and decreases effort.

Increasing pressure support would boost ventilation but doesn’t address the trigger problem and can worsen hyperinflation. Switching to a lower CPAP would worsen triggering. While making trigger sensitivity more aggressive could help, in the presence of significant auto-PEEP offsetting external PEEP is the more effective immediate strategy.