Episode #60 Safety Considerations for High-Flow Nasal Oxygen Delivery

Hello and welcome back to the Anesthesia Patient Safety Podcast.  My name is Alli Bechtel and I am your host. Thank you for joining us for another show. One of the themes for this podcast is highlight some of the most popular articles from the APSF website. Today’s show will be no exception! There are many threats to patient safety that anesthesia professionals need to watch out for including difficult airway management, operating room fire risk, and oxygen delivery to avoid hypoxemia. On the show today we will be reviewing an article that combines all three of these important topics. So, get ready!

Before we dive into today’s episode, we’d like to recognize Fresenius Kabi, a major corporate supporter of APSF. Fresenius Kabi has generously provided unrestricted support to further our vision that “no one shall be harmed by anesthesia care”. Thank you, Fresenius Kabi- we wouldn’t be able to do all that we do without you!”

Today’s triple threat for patient safety is brought to us by authors, Cooper, Griffiths, and Ehrenwerth for their article, “Safe Use of High-Flow Nasal Oxygen With Special Reference to Difficult Airway Management and Fire Risk” from the October 2018 APSF Newsletter. To follow along with us, head over to APSF.org and click on the Newsletter headings. Fifth one down is the Newsletter Archives. Then scroll down until you get to October 2018. Then, look over in the left-hand column and scroll down until you come to our featured article today. I will include a link in the show notes as well.

Before we get into the article, I reached out to the authors to provide some exclusive content. Jeremy Cooper submitted several quotes for this podcast. Cooper is an anesthesia consultant who practices cardiothoracic anesthesia at Auckland City Hospital in New Zealand and we are so happy to have him contribute content from across the pond. First up, I asked Cooper why he and his colleagues wrote this article. I am going to read his response now.

Cooper wrote, “We wrote the article as a project that came out  of Jan [Ehrenwerth]’s thoughts. This in turn is because Jan and I have collaborated in the past on education about fires. Jan, as you know has for years done the annual ASA lecture on OR fires. This is his area of expertise. I  had made a movie about airway and OR fires, in the days before the APSF made their own movie about fires, and Jan used it at the ASA -since parts of it are outrageous. The movie is on You tube and if you look under “Anesthesiology Thermal Injury” it’s the first hit.”

Okay, I am going to stop there for a minute because I did just want Cooper suggested and I watched the video that he created that is available on You tube. It is less than 5 minutes long and provides tons of information about operating room fires. I will include a link to the video in the show notes so go check it out after you finish listening to this podcast.

Cooper continues with his response about why he wrote the article: “Then, I started to communicate to Jan about the fire risk of High Flow Nasal Oxygen. He suggested that we write an article about this and then it grew to be a project about HFNO in total, not just about HFNO and fires.

The reason for me getting into fire risk dates back many years when I was an expert witness in a medico legal case about airway fires under anesthesia… I made the movie after this.

More lately we had a visiting UK  HFNO world  expert ENT surgeon do a years work with us  in NZ and he DID NOT know anything about potential fire risk….He publishes a lot about HFNO. He was until then advocating using laser when also using HFNO. He did a complete 180 degree turn once he  learnt from us about the fire risk of HFNO. Since we wrote the article for the APSF there have been several laser/HFNO  fires that I know of, one at least causing considerable patient harm. I suspect that many fires like this  will not be published since the manufacturer of the system used prohibits use of lasers with HFNO.”

Next up, I asked Cooper what he hopes to see going forward with regard to the use of High Flow Nasal Oxygen. This is what he wrote: “ I envisage that HFNO use will evolve and I hope with not too many fires on the way. Blenders to reduce the % of oxygen in the HFNO will be an advantage and we have this now. The use of HFNO for Covid cases has exploded obviously and this use will be a source of publications more than anesthesia I would guess.” Keep listening because we will be hearing more from Cooper at the end of the show.

Now, it is time to get into the article. Here we go.

[Woosh of Air Sound]

The authors start by introducing the technology of High-Flow Nasal Oxygen which may be used in the ICU for patients with acute hypoxic respiratory failure in order to try to avoid intubation or for patients who need additional support following extubation. It has also been studied for use in the operating room. You may have heard this technology called THRIVE or Transnasal Humidified Rapid-Insufflation Ventilatory Exchange. In the article as well as on the show today, we will focus on the use of high-flow nasal oxygen for adults rather than any applications for pediatric patients. If you have not seen a system for high-flow nasal oxygen delivery before, then I encourage you to go to the article because the authors include a labeled picture for reference.

Let’s take a minute to review the differences between standard nasal cannula oxygen flow and delivery compared to high-flow. For standard low-flow nasal cannula oxygen delivery, the oxygen flow rates are usually set between 2-10 liters/minute. For a patient breathing spontaneously on 2-4 liters/minute nasal oxygen with a typical inspiratory flow rate of 20-40 liters/minute, this will yield an effective delivered oxygen concentration  to the lungs of about 25-30%. This occurs since the inspiratory flow rate is greater than the oxygen flow rate from the nasal cannula leading to entrained room air which lowers the FiO2. High-flow nasal oxygen can be set for oxygen flows between 50-100 liters/minute. As a result, the nasal oxygen flow delivered is greater than the patient’s inspiratory flow rate so very litter room air is entrained and the effective delivered oxygen concentration may reach 95-100%.

Let’s take a closer look at this technology. The High-flow nasal oxygen delivery system includes the following components:

1. An electrically powered high-pressure oxygen/air supply (ideally with a blender to blend air into the gas flow to reduce the FiO₂if needed)
2. A flowmeter capable of flows of up to 100 liters per minute
3. A humidifier capable of fully humidifying the inspired oxygen/air mixture
4. Wide bore tubing to deliver gas from the gas supply to the nasal cannula. And finally,
5. A specialized wide bore nasal cannula to deliver the oxygen/air blend from the gas tubing to the patient’s nose.

This is more complex than a standard low-flow oxygen nasal cannula set up, but there are some benefits to using high-flow from a physiologic perspective. These benefits cannot be accomplished with low-flow nasal oxygen delivery. The authors reports that some of these benefits include the following:

First, high flow is able to provide continuous positive airway pressure or CPAP. In addition, it can remove CO2 from the respiratory dead space and enable oxygen diffusion in the alveoli. Other important benefits include decreased work of breathing and decreased airway resistance. The high flow nasal oxygen delivery system may be used for patients during general anesthesia, sedation cases, or in awake patients and it can be modified to delivery up t 95-100% oxygen or mixed with air to provide a lower FiO2 when appropriate.

Since we just talked about the benefits, we need to turn our attention to the relative and absolute contraindications of high-flow nasal oxygen. When are the times when the use of this technology is absolutely contraindicated?

• Anytime an alcohol-based skin preparation solution is used in combination with HFNO due to the increased fire risk
• For patients with known or suspected skull base fractures, CSF leaks, or any other communication from the nasal cavity to the intracranial space
• Patients who have a significant pneumothorax and there is no chest tube in place since there is a risk for expanding the pneumothorax.
• For patients with complete nasal obstruction
• And finally, for patients with active epistaxis or for patients who have undergone recent functional endoscopic sinus surgery or a (FESS) procedure.
• Another scenario that you will want to avoid is the combination of a high-flow nasal oxygen cannula under a tightly sealed face mask with a closed APL valve on the anesthesia machine which could lead to significant pressure buildup.

There are some important relative contraindications to keep in mind as well. High-flow nasal oxygen may need to be avoided in patients with the following:

1. A partial nasal obstruction
2. A disrupted airway for example in patients with a laryngeal fracture, mucosal tear, or tracheal rupture.
3. A contagious pulmonary injection and the authors give the example of tuberculosis since this article was written prior to the start of the current Covid-19 pandemic.
4. A nasal infection which could lead to pulmonary seeding of the infection. However, this is a theoretical concern and this has not been demonstrated at the time when this article was written.
5. A history of bleomycin or certain chemotherapy agent administration. These patients should not receive high concentrations of oxygen because this may lead to pulmonary toxicity in the example of Bleomycin.
6. Age less than 16 years old due to the increased risk for pneumothorax from air-leak syndrome

In addition, the use of high-flow nasal oxygen is relatively contraindicated for patients who cannot tolerate hypercarbia and are at risk for prolonged apnea. This cohort of patients may include those with sickle cell anemia, pulmonary hypertension, intracranial hypertension, and congenital heart disease. Keep in mind that for patients undergoing a procedure with the use of a laser or electrocautery in an area near the head or neck, there is an increased fire risk if high-flow oxygen is used. The authors caution that this becomes an absolute contraindication for high-flow oxygen delivery if the FiO2 needs to be maintained greater than 30% due to the high risk for fire.

There is still so much to talk about when it comes to High-flow nasal oxygen so you will have to join us next week when we talk about clinical applications of this technology. We will also review risks and benefits of the use of high-flow nasal oxygen for certain situations such as under the surgical drapes, during emergent awake tracheostomy placement, and during elective airway surgery. We will conclude by looking at considerations for fire risk assessment in the operating room with the use of high-flow nasal oxygen. You do not want to miss the show next week.

Before we wrap up the show today, Dr. Cooper highlighted the work of some of his colleagues that he collaborated with for this article. This is what he wrote: “My passion is education and I can write OK , and Jan and I did much of  the spadework on writing the article. Ben Griffiths is a master of difficult airways and uses the HFNO many weeks of the year (more than me) and was my go to guy for the practical questions. Fisher and Paykel make the device we use and are truthful and ethical and great people to work with, and we have done research on HFNO together.”

Thank you so much to Cooper for his contributions to the show today. We are looking forward to hearing more from you during the show next week.

If you have any questions or comments from today’s show, please email us at [email protected].

Visit APSF.org for detailed information and check out the show notes for links to all the topics we discussed today.  Please keep in mind that the information in this show is provided for informational purposes only and does not constitute medical or legal advice. September is a big month for Patient Safety Panels and Educational Opportunities. You can check out the full listing at APSF.org and clicking on the Conferences and Events Heading. Some of the September events include the 17^th World Congress of Anesthesiologists, The APSF Board of Directors Meeting, The 2021 APSF Stoelting Conference with the theme, “”Clinician Safety: To Care is Human,” and the Sepsis Alliance Summit which will coincide with Sepsis Awareness Month. For more information about these events head over to the website and I will include a link in the show notes. If you are attending any of these events, be sure to share your experience on Twitter and tag us @APSForg. We can’t wait to hear from you!

Until next time, stay vigilant so that no one shall be harmed by anesthesia care.

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