PEEP

Source:http://www.uptodate.com/contents/positive-end-expiratory-pressure-peep?source=see_link&anchor=H9#H9

Positive end-expiratory pressure (PEEP) is the alveolar pressure above atmospheric pressure that exists at the end of expiration. There are two types of PEEP:

PEEP that is provided by a mechanical ventilator is referred to as applied PEEP (also called extrinsic PEEP)
PEEP that is secondary to incomplete expiration is referred to as auto-PEEP (also called intrinsic PEEP).
Clinical aspects of PEEP are discussed in this topic review. The strategy of high PEEP that has been investigated in patients with acute lung injury or acute respiratory distress syndrome is described separately. (See "Mechanical ventilation in acute respiratory distress syndrome", section on 'High PEEP'.)

APPLIED (EXTRINSIC) PEEP

Applied PEEP is usually one of the first ventilator settings chosen when mechanical ventilation is initiated. It is set directly on the ventilator. (See "Overview of mechanical ventilation", section on 'Initiation'.)

Indications — A small amount of applied PEEP (3 to 5 cmH2O) is indicated for most patients undergoing mechanical ventilation because it mitigates end-expiratory alveolar collapse, a consequence of the endotracheal tube bypassing the glottic apparatus [1]. Such low levels of applied PEEP are occasionally referred to as physiologic PEEP, while higher levels are called supraphysiologic PEEP