Challenges of mechanical ventilation in unilateral pneumonia: is PEEP the answer?

Excerpt

Pneumonia remains a common cause of respiratory failure for which invasive mechanical ventilation is often needed. Although mechanical ventilation (MV) saves lives, it also has the potential to add to the original lung insult, if not used judiciously. Recent clinical trials have convincingly demonstrated that the outcome of critically ill, ventilated patients is at least partially determined by the ventilatory strategy employed [1, 2]. Such trial designs were based upon key concepts tested in experimental models of ventilator-induced lung injury (VILI), highlighting the clinical utility of such models. Experimental ventilatory strategies that lead to VILI generally have excessively high tidal volumes and/or low levels of positive end-expiratory pressure (PEEP) [3]. The former ventilatory pattern predisposes lungs to alveolar overstretching (volutrauma) while the latter may cause alveolar instability and cyclic opening and collapse of the distal airways (atelectrauma). Despite mechanistic differences, both types of insult have been associated with epithelial and endothelial disruption, permeability alteration and inflammation. This sequence of events is not well characterized. The ability of different ventilatory strategies to alter lung and blood cytokine levels has, however, been demonstrated [4, 5]. In pneumonia models, different patterns of ventilation have been found to modulate the risk of bacteremia [6, 7, 8], presumably by altering the integrity of the alveoli-capillary barrier. …