June 4, 2015
High-Flow Oxygen through Nasal Cannula in Acute Hypoxemic Respiratory Failure
What was the research question?
Does the use of high-flow oxygen therapy or noninvasive ventilation therapy in patients admitted to the ICU with nonhypercapnic acute hypoxemic respiratory failure result in a lower rate of endotracheal intubation and better outcomes when compared to standard oxygen therapy alone?
How did they do it?
A prospective, multicenter, randomized, controlled trial conducted in 23 ICUs in France and Belgium.
310 clinically matched patients aged 18 years with acute hypoxemic respiratory failure who were admitted to the ICU were enrolled.
Patients were randomly assigned to one of three treatment groups according to a centralized Web-based management system: Standard oxygen therapy (94), High-flow oxygen therapy (106), and Noninvasive ventilation (110).
Oxygen levels were adjusted to maintain a minimum oxygen saturation of 92%. High-flow oxygen was applied for at least 2 days, while noninvasive ventilation was applied for at least 8 hours per day for 2 days. High-flow oxygen was used between noninvasive-ventilation sessions.
The primary outcome was the proportion of patients who required endotracheal intubation within 28 days after randomization.
Secondary outcomes included ICU mortality, 90-day mortality and duration of ventilator-free days within the first month.
What did they find?
Day 28 intubation rates were 38% for high-flow oxygen, 47% for regular oxygen, and 50% for noninvasive ventilation (P = 0.18; P = 0.17 by the log-rank test).
At day 28, the high-flow oxygen group had significantly more ventilator-free days than the conventional oxygen group or the noninvasive ventilation group (24 days vs. 22 days vs. 19 days, respectively; P=0.02 for all comparisons).
90-day mortality yielded hazard ratios of 2.01 (95% confidence interval [CI], 1.01 to 3.99) (P=0.046) when comparing standard oxygen to high-flow oxygen & a hazard ratio of 2.50 (95% CI, 1.31 to 4.78) (P=0.006) with noninvasive ventilation versus high-flow oxygen.
What are the limitations?
Due to the nature of the intervention, blinding was not possible.
Potentially lack of external validity due to the study being extremely controlled and conducted in specific regions and demographics.
The sample size of the study was inadequate to produce significant results in the rate of intubation, reducing statistical power and dependability of the results and raising the possibility of type II errors.
What does it mean?
Treatment with high-flow oxygen, standard oxygen, or noninvasive ventilation did not produce significantly different intubation rates. Nonetheless, the 90-day mortality rate showed a substantial difference in favor of high-flow oxygen.
The result suggests that high-flow oxygen therapy may represent a reasonable option to noninvasive ventilation or standard oxygen therapy in patients with non-hypercapnic acute hypoxemic respiratory failure in terms of mortality. However, to direct clinical practice, more studies with bigger sample sizes are required, as well as consideration of unique patient variables.