PEEP = Positive end-expiratory pressure; airway pressure higher than zero at the end of exhalation

 

Extrinsic PEEP (PEEP E ) = a ventilator value for PEEP set by the operator

 

Intrinsic PEEP (auto-PEEP, or PEEP I ) = the amount of pressure in the lungs at the end of exhalation when expiration is incomplete (expiratory flow is still occurring) and no PEEP E is present (PEEP E is excluded from this value)

 

Auto-PEEP can occur in three circumstances: (1) Strong active expiration, often with normal or even with low lung volumes; e.g., Valsalva maneuver; (2) High minute ventilation (>20 L/min), where T E is too short to allow exhalation to functional residual capacity, or when expiration is inhibited by resistance external to the patient such as a partially obstructed expiratory filter; (3) Expiratory flow limitation due to increased airway resistance, as may occur in patients with COPD on mechanical ventilation or with small endo­tracheal tubes or obstructed (clogged) expiratory filters.

Total PEEP = PEEP E + PEEP I