Intrinsic (or auto-) positive end-expiratory pressure during spontaneous or assisted ventilation

Abstract

The mechanisms generating intrinsic or auto-positive end-expiratory pressure (PEEP) during controlled mechanical ventilation in a relaxed patient also occur during spontaneous breathing or when the patient triggers the ventilator during an assisted mode [1, 2]. These include an increased time constant for passive exhalation of the respiratory system, a short expiratory time resulting from a relatively high respiratory rate and/or the presence of expiratory flow limitation. Whereas dynamic hyperinflation and intrinsic or auto-PEEP may have haemodynamic consequences, this is not frequently a major concern in spontaneously breathing patients or during assisted ventilation because the spontaneous inspiratory efforts result in a less positive or more negative mean intrathoracic pressure than during controlled mechanical ventilation. The main consequence of dynamic hyperinflation during spontaneous and assisted ventilation is the patient's increased effort to breathe and work of breathing [1, 2]. © 2006 Springer-Verlag Berlin Heidelberg.