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:
- Intracranial surgeries
- Particularly when MAP is low
Top contributors: Tony Wang