Positive End Expiratory Pressure (PEEP)
OVERVIEW
- PEEP is the maintenance of positive pressure within the lungs at the end of expiration (positive end expiratory pressure)
- in spontaneous ventilation using non-invasive ventilation (NIV) the equivalent is CPAP (continuous positive airway pressure)
- high PEEP is used as part of an Open Lung Approach To Ventilation
ADVANTAGES
- increased airway pressure
- increased FRC (prevention of airway collapse)
- increase PaO2: increased capillary-alveoli interface for gas exchange, extra-vascular lung water displaced from alveolar interstitium to peribronchial interstitium)
- maximises recruitment of alveoli by preventing cyclic de-recruitment on expiration
- decreased airway resistance
- reduced V/Q mismatch
- improved distribution of inspired gas
- reduced work of breathing
- prevention of surfactant aggregation reducing alveolar collapse
- reduction in LV afterload (due to increased LV transmural pressure) — decreased preload and WOB also help in APO
DISADVANTAGES
- impaired CO2 elimination
- decreased RV preload, increased RV afterload, decreased LV compliance (due to intra-ventricular septum displacement)
- reduced urine output through increased ANP, decreased GFR and increased ADH