Sunday, March 8, 2015

High-flow nasal cannulas: Not yet ready for ED use.

What is high-flow nasal cannula (HFNC) therapy, and, more importantly, does it work? A recent segment on EM:RAP went into a fair amount of detail about the putative mechanism, so I’ll leave that alone.

What that segment left out, though, was any discussion of the published evidence pointing to the benefit of HFNC. And indeed, while there are a lot of anecdotal reports and personal testimonials, the actual data hasn’t been clearly discussed. Here’s a quick review of what we currently know.

1. Preterm infants

Although the “diet-PEEP” argument would suggest that HFNC might have a large role in tiny patients, it isn’t clear that HFNC helps prevent intubation in preemies. A Cochrane review suggested that using HFNC post-extubation, instead of CPAP, might lead to higher re-intubation rates. An RCT that was conducted after that review, however, found that HFNC was roughly equivalent to nasal CPAP for respiratory support in this age group. Data from other recent trials haven’t been as convincing, though, and many neonatologists still find the evidence “insufficient” to use HFNC in place of more established therapies

2. Infants

It may help prevent intubation of little kids with bronchiolitis, although the data is weak. The two most relevant studies were retrospective chart reviews, using a before-and-after design, looking at overall rates for intubation in the time period after HFNC was introduced to the pediatric service. Nonetheless, McKiernan found that intubation rates for bronchiolitis dropped from 23 % to 9%, and Schibler found the rate plummeted for 37% to 7%!
McKiernan 2010
This may end up being one of the best-supported roles for HFNC, and high-quality studies are in progress that could help clarify the issue.

3. Adults

The initial trials in adults have demonstrated modest improvements in oxygenation, but haven't studied patient oriented-outcomes. For example, one study found that oxygenation mildly increased after HFNC initiation, but no control group was used.

Sztrymf 2012

In one controlled trial, versus face mask, fewer desaturations were seen with HFNC. Despite this, there was no statistical difference in the use of rescue CPAP/BiPAP. A few other studies have further noted that HFNC seems to be more comfortable than CPAP.

A single-author review, otherwise very bullish on HFNC therapy, conceded: “although some clinicians may have the impression that in some instances, use of HFNC has avoided intubation, this has not been shown in a controlled trial.”

The largest current review on the use of HFNC concludes that (my emphasis):
“While theoretical advantages exist over standard nasal cannula and face mask oxygen, current evidence does not definitively demonstrate superiority to other methods of respiratory support. Few studies have focused on clinical outcomes beyond common respiratory parameters. Given the potential lack of consistency of positive pressure generated with current HFNC systems, NIV such as CPAP and bilevel positive airway pressure should still be considered first line therapy in moderately distressed patients in whom supplementation oxygen is insufficient and when a consistent positive pressure is indicated.”

Bringing it home!

Being an “early-adopter” is cool – if you’re lining up to get the new iPhone or Zune! In medicine, however, it doesn’t often pay to jump on a bandwagon before the data is in. (Want to buy some Xigris cheap?) We are being encouraged to try a new therapy that uses proprietary (proprietary = $) devices, with soft indications, scant evidence, but with touted outcomes such as “improved comfort,” instead of mortality or rates of intubation. We should be cautious.

Particularly concerning is the uncritical enthusiasm for the use of this device in situations that either clearly call for other therapies, or for no therapy. For example, some describe the utility of HFNC in patients who are “extremely hypoxic,” but there is little evidence that HFNC improves outcomes in this population.

HFNC is probably more useful for precisely titrating FIO2 in the (mythical?) CO2 retainer. But if there is a concern about the PaCO2, why not use a proven therapy like NPPV that we know saves lives?

Lastly, some clinicians promote the use of HFNC for CHF, since there is (wink, wink) a “PEEP component,” but that’s a patient who needs CPAP or BiPAP as well, since we already have proven a mortality benefit in that population as well.

Sure, you can relax, talk with family, and eat while wearing HFNC, but if you are so dead set on wolfing down a sandwich, you probably don’t need an expensive, unproven therapy. You need 2 liters per minute, and a floor bed!


  1. Why do some clinicians insist on waiting for a collection of randomized prospective studies before adopting any new therapy? I understand EBM, and I know that for outcomes I cannot follow in the ED itself, I need to rely on good evidence based studies, many with large numbers of patients. However, for a therapy in which I can see a response myself in the department, I should be able to form my own opinion. Recognizing that the risks of confirmation bias can be controlled for by using objective measures, there is no reason to wait for a Cochrane review before trying a new therapy like High Flow Nasal Cannula.

    So does HFNC therapy work. Hell yes. We are just finishing our worst RSV season in years. Every EBM study ever written on bronchiolitis has stated nothing works for this disease. Not hypertonic saline, not nebulized epinephrine, not albuterol, nothing. But this season we used HFNC and found for the first time a therapy that did work. Infants and toddlers with retractions severe enough to reach their thoracic vertebrae, respiratory rates in the 80s and 90’s and ronchi, rales and wheezes in all fields were placed on HFNC. Within minutes respiratory rates dropped to the 40’s, sats increased and retractions improved. By 2 hours most of these kids had clear breath sounds. Now before you tell me this is confirmation bias, I will tell you in 36 years I have tried everything in these children and nothing has worked. More importantly, I had the same expectations of all of those therapies as I had for HFNC and was not deluded by any confirmation bias into thinking I was making these children better. The nurses, myself and the most skeptical, late adopters in our department have all reported the same experiences with the HFNC.

    I have had similar experiences with adult patients (with the exception of CHF, BiPAP still works better in them).

    So here is my question. On your next shift if a mom brings in a struggling 8 month old with severe respiratory distress and obvious bronchiolitis are you going to do nothing, which is what the EBM literature recommends or are you going to try HFNC on the recommendation of some very experienced clinicians?

    Alfred Sacchetti, MD
    Emergency Department
    Voice: 856-757-3803

  2. As I noted above, the (quite messy) data on HFNC use in bronchiolitis suggests that HFNC could be an effective tool where, indeed, very little else works. I look forward to seeing the better-controlled trials, and I hope that it shows a benefit!

    I don’t think any working EM physician requires an RCT or a Cochrane review to justify every intervention. Our world “in the pit” is too messy to survive as EBM absolutists, and so I think that the “some clinicians” argument is a bit of a straw-man. Evidence doesn’t have to be based in double-blind, multicenter RCTs to be valid, but it ought to be a little better than what we have now for the utility of HFNC in COPD, asthma, CHF, or other hypoxic or hypercarbic causes of respiratory failure. As it stands, the evidence from modestly well-done studies shows only tepid benefit (e.g. “improved comfort”) in adults. Surely that evidence should outweigh case studies and anecdotes?

    For every clinician who you might describe as a forward-thinking “early-adopter,” I can point to another clinician who jumped on a bandwagon too soon. Did your hospital purchase a bunch of Edwards catheters for sepsis care, or expensive devices for inducing hypothermia after cardiac arrest? Did your pharmacy purchase a bunch of Xigris or nesiritide that gathered dust before being withdrawn from the market place? Following the latest fad can make you a pioneer, or it can hurt patients and cost big $$.

    So, if we already have therapies with proven benefit, why change to something new, with only “Mikey likes it” levels of evidence?

  3. Sorry gotta disagree strongly. All of the examples you cite contained outcomes that could not be observed in the ED. As a result clinicians needed to rely on evidence based medicine for guidance. HFNC has an outcome that is immediately observable to the treating clinician. You are looking at the patient, if you close the laryngoscope and put the intubation cart away the treatment worked.

    You condemn the early adopters but you ignore all those conservative docs who waited before adopting therapies that turned out to be much more superior to existing treatments.

    How do you regard those ED docs who held off adopting BIPAP for years waiting for the RCT’s to convince them it was a good therapy. How do you justify the unnecessary intubations with all the procedural complications, ventilator associated pneumonias and ICU admissions. If you waited for ED studies to prove the value of propofol sedation you subjected patients to increased complications with less effective agents and prolonged ED stretcher times. Even something as simple at using wire guided pig tail catheters for pneumonthoracies has yet to undergo a RCT, yet every progressive department has adopted them over the traditional formal chest tubes in these patients.

    Here is the bottom line. You can be wrong as an early adopter if a therapy turns out to be ineffective. You can be wrong for waiting too long to adopt a much more effective therapy. For me the real error is to condemn a new therapy with outcomes observable in the ED without ever trying it. Until you have used HFNC in a pulmonary fibrosis patient to avoid an intubation or in a tiring infant with bronchiolitis you really cannot condemn the therapy. There is no reason anyone reading this blog cannot take this modality and use it for themselves.

    Like Mikey, you just might like it.

  4. This comment has been removed by the author.

  5. You don't need a randomized control trial to dictate all you management. You can still look out the outcome of the patient in front of you. High Flow Nasal Cannula is inexpensive, clinically effective and provides improved comfort beyond simply avoiding intubations. As those old enough to remember Mikey, "Try it, you'll like it"

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