May 272015

Noninvasive ventilation (NIV), often referred to by the trade name “BiPAP®,” can prevent intubation and save lives in patients with COPD exacerbations or pulmonary edema due to heart failure. Its proven benefits and low risk have led to NIV being used for patients in respiratory failure in virtually every acute care setting in the developed world.

Noninvasive ventilation reduces the work of breathing and increases the bulk flow of air, which may be why its benefits are especially pronounced in patients with hypercarbic respiratory failure (high pCO2, with or without significant hypoxia).

New systems for providing high flow oxygen by nasal cannula have entered wide use in recent years (Optiflow, Vapotherm). These systems can deliver flow rates of 50 liters/minute of heated and humidified oxygen at concentrations up to 100%.

Some experts argue high-flow oxygen is better suited to acute hypoxemic respiratory failure than is NIV; a new study in the New England Journal of Medicine suggests they may be right.

Authors randomized 310 patients with acute hypoxemic respiratory failure (PaO2:FiO2 < 300 mm Hg) at 23 ICUs in France and Belgium to receive either noninvasive ventilation, high-flow oxygen by nasal cannula, or oxygen by face mask (n~100 in each arm).

About 80-90% of enrolled patients' hypoxemia was due to pneumonia. Most had low or normal pCO2 levels at enrollment, and all had pCO2 ≤45 mm Hg. The makers of Optiflow donated equipment for the study, but had no other involvement, according to the authors.

At day 90, those receiving high-flow nasal cannula oxygen were about twice as likely to survive as were those receiving either face mask oxygen or noninvasive ventilation. Patients receiving NIV had the highest mortality at 25%, vs 11% for those assigned to high-flow oxygen by nasal cannula.

At 28 days, numerically fewer patients receiving high-flow oxygen by nasal cannula needed mechanical ventilation. This finding didn't reach statistical significance, but the high-flow oxygen patients did have significantly more ventilator-free days.

The advantages of high-flow oxygen by nasal cannula appeared greatest in the most hypoxemic patients (PaO2:FiO2 < 200 mm Hg). Only ~30% in this post hoc subgroup receiving high-flow nasal cannula oxygen required intubation vs. ~55% of those receiving face mask oxygen or NIV.

Patients receiving high flow nasal cannula oxygen also reported greater comfort and less dyspnea than those in the other arms.


takeawayClinical Takeaway: Noninvasive ventilation’s benefits were shown in hypercarbic respiratory failure, primarily exacerbations of COPD and heart failure. This study suggests that in patients with hypoxemic respiratory failure without hypercarbia (such as due to pneumonia), high-flow oxygen by nasal cannula may be superior, and should be considered as first line treatment instead of NIV.

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High flow oxygen by nasal cannula saved lives over noninvasive ventilation