The role of PEEP in patients with chronic obstructive pulmonary disease during assisted ventilation.

In patients with acute respiratory failure (ARF) due to acute exacerbation of chronic obstructive pulmonary disease (COPD), the intrinsic positive end-expiratory pressure (PEEPi) can significantly increase workload for ventilation. It has been suggested that, in the presence of expiratory flow limitation, application of low levels of PEEP by the ventilator can be used to reduce PEEPi and therefore the magnitude of the inspiratory effort during assisted mechanical ventilation (or pressure support) and weaning. Clearly, pulmonary hyperinflation should not be further enhanced in order not to counteract the beneficial effect of removing PEEPi by decreasing respiratory muscle length and force. This use of PEEP in COPD patients is supported not only by theory, but also by recent experimental work, although sufficient clinical information is not yet available to provide a guideline for titration of the PEEP level. Therefore, application of PEEP in COPD patients requires close monitoring of the end-expiratory lung volume. This can be accomplished, among other noninvasive ways (e.g. the inductive plethysmography), by inspection of flow/volume curves during application of increasing levels of PEEP. The shape of the expiratory limb of the flow/volume curve can also suggest the presence of dynamic hyperinflation and expiratory flow limitation.