Assessment of PaO2/FiO2 Ratio Pre and POst INTubation

We designed this study to dtermine whether invasive mechanical ventilation (MV) would have an impact on the reclassification of patients with acute hypoxemic respiratory failure (AHRF) -treated previously with non-invasive respiratory support- into categories of severity (mild, moderate, and severe). Our hypothesis is that the assessment of PaO2/FiO2 ratio on PEEP greater or equal to 5 cmH2O after intubation, in patients labeled as mild/moderate/severe AHRF while on non-invasive respiratory support, would identify that a marked proportion of patients would change the degree of severity after a brief period of invasive MV