Positive End Expiratory Pressure

PEEP maintains constant positive pressure in the lungs throughout exhalation so that airway pressure does not fall to atmospheric pressure.

PEEP can be used with any mode of ventilation. Pressures vary from 3cmH2O to 20cmH2O. 

PEEP boosts SaO2, as it keeps the airways open allowing increased ventilation through collateral ventilation. Other ways of increasing SaO2 include increasing FiO2, prolong the plateau and increase the inspiration:expiration ratio. 

Positive effects include:

• Stability of alveoli and conservation of surfactant
• Resting lung volume out of the range of airway closure
• Increased alveolar ability for gas exchange

Complications include:

• Excess PEEP leads to hyperinflation which does not increase recruitment for gas exchange
• Reduced venous return and cardiac output
• Increased risk of barotrauma
• Increased CVP due to increased pressure in the thoracic cage