auto-PEEP

Introduction

A build-up of positive-end-expiratory pressure (PEEP) that may occur during mechanical ventilation.

Etiology

• compromised exhalation (high airway resistance)
  • obstructive lung disease
    • asthma
    • COPD
  • small or obstructed endotracheal tube
  • long ventilator tubing
  • ARDS (increased flow resistance)
• high demand for ventilation (> 12-15 L/min)
• short expiratory time
• inverse ratio ventilation (IRV)

Pathology

• excessive tidal volume &/or minute ventilation can result in auto-PEEP & high alveolar pressures
• occurs when the expiratory phase is truncated prior to completion of exhalation
• airflow still occurs at end-exhalation, resulting in positive pressure in the alveoli at end exhalation
• auto-PEEP reduces cardiac output

Clinical manifestations

• wheezing
• marked expiratory prolongation
• drop in blood pressure (hypotension)
• restlessness

Diagnostic procedures

• pulmonary function testing
  • flow-volume loop on ventilator reveals continuous expiratory flow until the start of inspiratory flow

Management

• disconnect the endotracheal tube from the ventilator & reconnect after a few seconds
  • this allows for release of pulmonary pressure due to auto-PEEP
  • change settings to allow for more expiration time
• treat airway obstruction
• decrease respiratory rate or tidal volume
• decrease peak inspiratory flow rate
• allow permissive hypercapnia (best option for ALI, ARDS)
• sedate or paralyze patient

More general terms

• positive end-expiratory pressure (PEEP)