Dynamic hyperinflation and intrinsic PEEP during mechanical ventilation

Abstract

Dynamic hyperinflation, also called intrinsic PEEP (PEEPi,) occurs particularly when high tidal volumes or high respiratory rates are used during mechanical ventilation, although the phenomenon does occur at normal tidal volumes. It is not identified using existing monitoring such as the airway pressure but can be identified by occlusion of the expiratory port before the onset of the next positive pressure breath. Many factors contribute to PEEPi which has unfavourable effects on respiratory muscle activity. Inhomogenicity of the time constants is a major aetiological factor. Fine tuning of positive pressure ventilation, using low tidal volumes, short inspiratory times and adequate inspired oxygen are required. External PEEP, up to but not exceeding PEEPi, may be advisable. PEEP may be used therapeutically to improve gas exchange by inverse ratio ventilation or high frequency jet ventilation.