Introduction:

Non-invasive mechanical ventilation (NIV) is a valid, albeit non-consensual option for the treatment of patients with Acute Respiratory Failure (ARF). The following article has the main goal of identifying predictors of therapeutic response to NIV.

Methods:

Retrospective longitudinal study which included patients in an Intensive Care Unit in 2016 and 2017, in whom NIV was started once they developed de novo ARF (PaO2/FiO2 < 200). We included patients with community acquired pneumonia (CAP) and acute respiratory distress syndrome (ARDS) and compared NIV-responders to non-responders.

Results:

Between 2016 and 2017, 83 patients with de novo ARF were treated with NIV. Of those, 50 (60%) were treated successfully. The most common cause of ARF was CAP, which was successfully managed with NIV in 70% of cases. NIV-responders presented lower severity scores (APACHE 2; SAPS 2; SOFA) at admission (17.5; 37.5; 6 vs 22; 48; 9, p=0.014, p=<0.01 and p<0.01, respectively). Non-responders presented significantly lower arterial pH values at admission (7.35 vs 7.42, p<0.01), PaO2/FiO2 ratio (118 vs 145, p=0.03), higher seric lactate (2.2 vs 1.46, p<0.01) as well as need for vasopressor support (51.5% vs 30%, p=0.04). The change in the PaO2/FiO2 ratio within 2 hours of treatment was wider in the group of NIV-responders, unlike non-responders (+53, p<0.01 vs +14, p=0.09).

Conclusion:

NIV was an effective respiratory support strategy in 60% of patients with de novo ARF. Patients who seem to have a higher probability of NIV success are: patients with CAP; with or without moderate ARDS, rather than severe; with no respiratory acidaemia; patients with no lactacidemia or patients with no need for vasopressor therapy. The ability of NIV to significantly alter the PaO2/FiO2 ratio after 2 hours of technique seems to be a good success predictor.

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