STUDY OBJECTIVE: High-flow nasal cannula is a new method for delivering high-flow supplemental oxygen for victims of respiratory failure. This randomized controlled trial compares high-flow nasal cannula with conventional oxygen therapy in emergency department (ED) patients with cardiogenic pulmonary edema.
METHODS: We conducted an open-label randomized controlled trial in the ED of Siriraj Hospital, Bangkok, Thailand. Patients aged 18 years or older with cardiogenic pulmonary edema were randomly assigned to receive either conventional oxygen therapy or high-flow nasal cannula. The primary outcome was the respiratory rate 60 minutes postintervention.
RESULTS: We enrolled 128 participants (65 in the conventional oxygen therapy and 63 in the high-flow nasal cannula groups). Baseline high-flow nasal cannula and conventional oxygen therapy mean respiratory rates were 28.7 breaths/min (SD 3.2) and 28.6 breaths/min (SD 3.5). Mean respiratory rates at 60 minutes postintervention were lower in the high-flow nasal cannula group (21.8 versus 25.1 breaths/min; difference 3.3; 95% confidence interval 1.9 to 4.6). No significant differences were found in the admission rate, ED and hospital lengths of stay, noninvasive ventilation, intubation, or mortality.
CONCLUSION: In patients with cardiogenic pulmonary edema in the ED, high-flow nasal cannula therapy may decrease the severity of dyspnea during the first hour of treatment.
This is a small study showing no difference in clinically important outcomes.
Interesting paper but not practice-changing. Under-powered for critical outcomes and confirms that this is likely not ready for prime time.
The chosen endpoint (respiratory rate) is not perhaps the most important outcome during an episode of pulmonary oedema but noteworthy improvement nonetheless. There is a disappointing lack of discussion about how this treatment might work.
Given that the VAS analog dyspnea scale didn't change, not sure that the authors' contention that HFNC reduces dyspnea is supported by their data. Otherwise, very little clinical advantage over nasal cannula or NRBFM demonstrated for this intervention in a rather limited patient population. I don't think they made a very persuasive case for using NRBFM in preference to "conventional" modes of oxygenation for mild cardiogenic pulmonary edema.
The primary outcome of respiratory rate is clinically insignificant. Without demonstrating a benefit for patient-centric outcomes such as mortality or intubation rates, this is not of interest to emergency medicine clinicians.
This is a relatively small study of HFNC vs conventional oxygen in patients with cardiogenic pulmonary edema in the ED. A number of studies have compared HFNC with conventional oxygen in hypoxic patients - although I don't think any have specifically in cardiogenic pulmonary edema (they were included but not exclusive in the other trials). This trial has overall underwhelming results. HFNC decreased the respiratory rate by about 3 breaths/min, but did not alter any other clinical outcome. I am not sure how relevant it is to clinical practice given these results.
One concern is the avoidance of acute MI patients. It may not be easy to tell early in the course, and the use of high-flow O2 in these patients remains questionable at times.
This was a randomized controlled trial in patients with cardiogenic pulmonary edema and no indication for non-invasive or invasive ventilation. They used sealed opaque envelopes for randomization, which is a reasonable strategy to obtain allocation concealment. Given the nature of the intervention, the study was not blinded. This could have inserted a risk of bias, because the main outcome was measured at the bedside by the investigators. The use of an objective outcome (respiratory rate) was a good way to deal with this potential bias. They used a “modified” intention to treat analysis. This is probably acceptable, because it was pre-specified for both groups. Most importantly, there was no difference in patient important outcomes. Even though this was a well done study, the results do not justify widespread use of this device, which is certainly more expensive then the regular nasal cannula.