Two years ago Maggiore published a prospective RCT showing that post-extubation high-flow nasal cannula (HFNC) reduced the risk of reintubation among hypoxic patients (PaO2/FiO2 < 300). The article was explored on the blog and incorporated into practice at the Genius General ICU. This has helped us aggressively liberate patients from mechanical ventilation while simultaneously reducing our reintubation rate.
One remaining question is determining which patients benefit from post-extubation HFNC. My practice has generally been to use HFNC in patients felt to be at higher risk for reintubation. A fresh RCT in JAMA will revise this.
Hernandez 2016: Effect of post-extubation high-flow nasal cannula vs. conventional oxygen therapy on reintubation in low-risk patients.
This was a prospective, multi-center RCT to evaluate post-extubation HFNC among patients at the lowest risk for reintubation. In order to find the lowest-risk group, only patients intubated for >12 hours who met all of the following criteria were included:
- age <65
- body mass index < 30
- APACHE II score <12 at time of extubation
- absence of heart failure as cause of respiratory failure
- absence of moderate-to-severe COPD
- no hypercapnia detected during a spontaneous breathing trial
- absence of airway patency problems
- low risk for laryngeal edema (no more than one of the following criteria: female gender, intubated at least three days, and difficult intubation)
- no difficulty managing secretions (adequate cough or suctioning <2 times within 8 hours before extubation)
- simple weaning (defined as success on the first spontaneous breathing trial)
- fewer than two comorbid conditions
- intubated no longer than a week
- not accidentally extubated
527 patients were recruited at seven centers in Spain. Patients were randomized to receive conventional oxygen therapy or HFNC for 24 hours following extubation. HFNC was successful in reducing reintubation (the primary endpoint) from 12% to 5% (p=0.004). The number needed to treat (NNT) to prevent re-intubation was 14. All patients tolerated HFNC with no reported complications.
HFNC reduced the reintubation rate due to persistent post-extubation respiratory failure or inability to clear secretions from 8% to 0.8% (table below). As expected, HFNC didn't affect the rate of reintubation due to surgery or altered level of consciousness.
This was an extremely ambitious trial, because the authors went to great lengths to select the patients least likely to benefit from HFNC. Nonetheless, HFNC was quite effective, with a reasonably low NNT.
Tricks to success
Both Maggoire 2014 and Hernandez 2016 utilized two techniques which are probably essential to the success of a post-extubation HFNC strategy:
- Pre-emptive support: HFNC was initiated immediately following extubation. An important mechanism of HFNC is probably preventing respiratory fatigue and thereby avoiding respiratory failure (discussed previously here). Alternatively, waiting until the patient develops respiratory fatigue and only then starting HFNC would likely be less effective.
- Aggressive support: Maggiore 2014 used a flow rate of 50 liters/minute, whereas Hernandez 2016 had a protocol to increase the flow rate as high as the patient could tolerate. Regardless of how well the patient may be oxygenating, increasing the flow rate reduces the patient's work of breathing and thereby reduces the likelihood of respiratory failure.
Both Maggoire and Hernandez excluded patients with hypercapneic respiratory failure (in part because there is evidence supporting post-extubation BiPAP in this situation). Thus, in a perfect evidence-based world these patients arguably might be treated with post-extubation BiPAP. However, it is often difficult to achieve compliance with post-extubation BiPAP, so these patients often wind up being treated with post-extubation HFNC instead. A RCT of BiPAP vs. HFNC among hypercapneic patients would be helpful.
How should this affect practice?
RCTs have proven that post-extubation HFNC improves surrogate endpoints, including reduced work of breathing and improved gas exchange (e.g. Parke 2013 and Rittayami 2014, reviewed here). Beyond these proof-of-concept studies, we now have two prospective RCTs showing that post-extubation HFNC reduces reintubation (Maggiore 2014, Hernandez 2016). The ability of HFNC to avoid intubation was also demonstrated in the FLORALI trial involving patients presenting with hypoxemic respiratory failure. Overall, these studies provide a strong evidence basis demonstrating that HFNC is safe, well tolerated, and effective, allowing some patients to avoid intubation.
Reintubation represents a major setback, which is psychologically discouraging to patients and associated with morbidity and mortality. As such, the potential benefits of HFNC likely outweigh any risks. Hernandez 2016 suggests that a broad population of patients might benefit from post-extubation HFNC, including patients at low risk of reintubation.
- Post-extubation HFNC has been shown in two RCTs to reduce the risk of reintubation.
- HFNC was effective even in patients at the lowest risk of re-intubation, among whom it had a NNT of 14 to prevent reintubation.
- For maximal benefit, HFNC should probably be started immediately after extubation and the flow rate increased to a high level (ideally to 50-60 liters/min).
- The best strategy to prevent reintubation among patients with hypercapnia remains unclear, because such patients were excluded from these studies.
The series on hemodynamics should resume next week, barring any other late-breaking events.
- Maggoire 2014: HFNC to avoid reintubation (PulmCrit)
- HFNC for early ventilator weaning (PulmCrit)
- The Bottom Line review of Hernandez 2016 by David Slessor (he has a different perspective on this article, so his post may be a good counterpoint to this post)
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