Mechanically ventilated patients can develop a condition in which air becomes trapped within the alveoli at end-expiration; this is called auto-PEEP.

Auto-peep has several adverse effects:

• Barotrauma from positive pressure trapped within the alveoli 
• Increased work of breathing
• Worsening pulmonary gas exchange
• Hemodynamic compromise secondary to increased intra-thoraic pressure

Auto-PEEP classically occurs in intubated patients with asthma or emphysema, but it may also occur in the absence of such disease. The risk of auto-PEEP is increased in patients with:

• Short expiration times (i.e., inadequate time for the evacuation of alveolar air at end-expiration)
• Bronchoconstriction
• Plugging of the bronchi (e.g., mucus or foreign body) creating a one-way valve and air-trapping

Auto-PEEP may be treated by:

• Reducing tidal volume
• Reducing the respiratory rate
• Decreasing inspiratory time
• Increasing PEEP

Patients may need to be heavily sedated to accomplish the above ventilator maneuvers.

References

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