Is there a subset of patients in whom pre-oxygenation with NRB or BVM could be safely pursued?  

Preoxygenation using an oxygen mask that does not provide positive pressure may be appropriate in patients who have a contraindication to noninvasive ventilation such as patients with active emesis. However, one of the key findings of the PREOXI trial was that preoxygenation with noninvasive ventila...