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Created: 19/2/2005

Positive End-Expiratory Pressure

PEEP is used as an adjunct to ventilation. It is produced by maintaining a positive airway pressure during expiration, usually of the order of 5-20 cmH2O. The addition of PEEP minimises airway and alveolar collapse and increases compliance (due to increase in FRC). This results in improved oxygenation and reduces shunt.

Undesirable effects of PEEP

If high levels of PEEP are used they may be a resultant increase in dead space. Intrathoracic pressure is raised, causing a reduction in cardiac output and possible barotrauma. Vasopressin release is increased (leading to reduced urine output) and ICP may also rise.

Indications for PEEP

PEEP may be used to reduce oxygen requirement and improve oxygenation.

Different levels of PEEP

 Best PEEP
Produces the least shunting without a significant reduction in cardiac output.

 Optimum PEEP
Produces the maximal O2 delivery with the lowest dead space/tidal volume ratio.

 Appropriate PEEP
Produces the least dead space.

 Intrinsic PEEP
The difference between alveolar pressure and airway pressure at end-expiration. It exists when expiration continues right up to inspiration. Often seen in airway obstruction, asthma, COPD, ARDS and in forced expiration. Also known as 'intrinsic PEEP'.

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