Non-invasive positive pressure ventilation in patients with acute respiratory failure

Non-invasive positive pressure ventilation is an emerging modality in contemporary critical care practice. Perhaps the most widely utilized and familiar form of non-invasive positive pressure ventilation is mask continuous positive airway pressure. Other common modes include mask Bi-level positive airway pressure and mask pressure support ventilation. All feature the delivery of positive airway pressure via a mask (full-face, naso-oral or nasal), and a patient-controlled respiratory cycle. The physiological benefits of non-invasive positive pressure ventilation suggested by a number of studies include improved oxygenation, decreased work of breathing, improved ventilation and perfusion matching, decreased fatigue, and increased minute ventilation. The utilization of non-invasive positive pressure ventilation has now been reported for a variety of clinical indications. In most, randomized trials are lacking, and the benefits and preferred mode of non-invasive positive pressure ventilation are still to be elucidated. In general, in patients that are candidates for endotracheal intubation, non-invasive positive pressure ventilation should be used as a way to possibly avoid endotracheal intubation rather than as an alternative to endotracheal intubation. Whilst the benefit of non-invasive positive pressure ventilation appears to be established in patients with chronic obstructive airways disease with hypercapnic acute respiratory failure, one of the major unresolved issues is whether one modality is significantly better than the others. Unfortunately, the question of whether Bi-level positive airway pressure is better than continuous positive airway pressure in this clinical scenario has not been satisfactorily addressed in any large randomized and controlled clinical trial. Further, there is no 'gold standard' for predicting success with non-invasive positive pressure ventilation, although several studies have looked at this aspect.