Positive end expiratory pressure (PEEP) is the amount of pressure that remains at the end of the expiratory phase which can be set in mechanically ventilated patients.

Benefits of PEEP

  • Increased FRC
  • Prevents closing of alveoli, thereby reducing airway opening pressure
  • Increase Palv, making West's zone move more caudally, thereby reducing physiologic shunt from Zone 3

Consequences of PEEP

  • Barotrauma/volutrauma: Increased peak airway pressure at high PEEP
  • Decreased venous return from IVC due to increased thoracic pressure
  • Decreased pulmonary blood flow
    • In patients with pulmonary hypertension, can worsen R heart strain
  • Elevation in ICP from less venous return, leading to decrease in cerebral perfusion pressure
    • CPP = MAP - ICP

Indications for PEEP

Most patients benefit from a small amount of PEEP to improve lung compliance. Patients who are obese may benefit from higher PEEP due to relative restrictive lung disease. Patients in Trendelenburg position and/or abdominal insufflation (e.g. laparoscopy) also benefit from PEEP due to elevated diaphragmatic pressures.

Optimal PEEP

There is little concensus about optimal PEEP. Typical ranges of PEEP are 0 to 15 cm H2O, more commonly 5 to 10 cm H2O.

Surgeries where PEEP should be used cautiously

Increased PEEP reduces venous return from IVC, which can increase venous bleeding in certain surgical cases:

  • Liver cases
    • Higher portal pressures and resulting in increased bleeding
  • Open prostatectomy
    • Increased blood pooling in dorsal venous complex, resulting in increased bleeding
  • Spine cases
    • Potential high risk complications with venous bleeding into spine

Increased PEEP resulting in elevation in ICP results in poor CPP, which should be considered with:

  • Brain surgeries
    • Particularly when MAP is low