There has been a growing trend toward delivering aerosolized medications using high-flow nasal cannula, but are HFNC an effective delivery method?
An asthma patient comes to the emergency room, unable to catch his breath, and gasps for air because of an inflamed airway.
An adult with pulmonary hypertension feels a crushing sensation in her chest and has trouble breathing.
A COPD patient struggles through the hospital entrance and steadies himself on a wheeled oxygen tank.
Almost all patients in respiratory distress admitted to the emergency room will need supplemental oxygen to ease the work of breathing and improve oxygenation. In a clinical setting, oxygen therapy can be administered through a nasal cannula, with lightweight tubes that fit into the nostrils. When aerosolized medications are needed, delivery of oxygen can be interrupted, contributing to the patients’ worsening respiratory status and levels of discomfort.
As a result, some respiratory care departments across the country have turned to administering aerosol medications for their critically ill patients through high-flow nasal cannula (HFNC), a heated, humidified system that administers high flows of oxygen and gas. Through a HFNC, oxygen and gas medications can be given to the patient at the same time, without interrupting either treatment or requiring more than one respiratory therapist. This can be especially appealing for respiratory therapists who want to avoid using multiple interfaces, said Awni Al-Subu, MD, medical director of Pediatric Respiratory Care at American Family Children’s Hospital in Madison, Wisconsin.
“There has been more and more interest in using the high flow as an interface to deliver aerosols to patients. In general, the biggest thing that people think about when they use it is: ‘I don’t have to combine multiple interfaces,” he said.
A recent study published in the journal Respiratory Care found that aerosol delivery by nebulizers can be efficiently combined with an adult HFNC circuit using low-flow oxygen in patients with chronic obstructive pulmonary disease (COPD).1 The researchers from Beni-Suef University in Egypt found that a vibrating mesh nebulizer with both a T-piece and large spacer provided higher pulmonary drug delivery than a jet nebulizer when combined with oxygen therapy via HFNC.
Additionally, patients may find delivery of aerosol therapy through HFNC more comfortable, which could increase compliance, and lead to better outcomes, according to a paper from researchers at Virginia Commonwealth University, published in Aerosol Science and Technology.2
One study, published in Pediatric Pulmonology, found that vibrating mesh nebulization within a high flow nasal cannula set to deliver a gas flow-rate of up to 4 liter per minute, in a full-term newborn infant appears to deliver equal or higher amounts of drug to the lungs as compared to standard aerosol facemask nebulization.3 “Performance is likely to be associated with a significant clinical effect when nebulizing bronchodilators in the clinical setting,” the authors wrote.
Respiratory therapists who treat children might find this therapy especially appealing since infants and children can present unique challenges for respiratory care providers.
They may not have the ability to coordinate their breathing with the treatment, causing a significant decrease in efficacy. Children who need such therapy are often in a state of distress, causing further irregularities in their breathing.
“When you are talking about [children], they are already in a hospital setting, they have anxiety, they don’t like things on their face. If you have the nasal cannula on their face and you have to remove it to put on a mask or use an MDI, that will not help with the comfort of the patient,” said Al-Subu.
Additionally, HFNC generates a low level of positive airway pressure, especially with the mouth closed.4 In hypoxemic patients, HFNC may provide effective support with greater ease of use and patient comfort than techniques requiring a face mask.
Higher flows not only enable the delivery of higher concentrations of oxygen, but also potentially provide increased respiratory support through continuous distending pressure, according to a paper coauthored by Al-Subu and published in Expert Review of Respiratory Medicine.5
While there appears to be several benefits to using HFNC to administer medications, some physicians and respiratory therapists are concerned that there still isn’t enough data to make the jump to HFNC. This is, in part, because there are a range of ways to administer aerosol medications through HFNC and the individual physiology of each patient can change the way the medication is taken into the lungs and processed by the body, said Al-Subu.
There’s also no standard definition of what constitutes “high flow,” making it a challenge to conduct research into the efficacy of the HFNC delivery of aerosol medications, said Natalie Napolitano, MPH, RRT-NPS, FAARC, a clinical specialist and researcher who works at Children’s Hospital of Philadelphia.
“There is very little scientific data out there that says this is effective. I don’t know that it is necessarily the most effective way to deliver aerosol therapy. And we don’t have data stating one way or the other. It is inconclusive at this point,” said Napolitano.
Al-Subu agrees that different respiratory therapists have vastly different ideas about appropriate flow rates. For instance, in pediatrics, many providers will administer about 4 liters per minute, some will give 8 liters per minute, but there is no consensus on how high the flow should be, he said. “There are a lot of controversial areas that we don’t have answers about.”
In a previous RT magazine article, Kenneth Miller, MEd, RRT-ACCS, RRT-NPS, wrote about respiratory therapists providing flow rates of up to 60 LPM. Miller explains that oxygen delivery devices are typically labeled as either low flow or high flow. Low-flow systems often are more comfortable, but the ability to deliver a precise oxygen concentration in various respiratory breathing patterns is limited. A high flow system can administer accurate oxygen concentrations, but some patients may find it uncomfortable.
In a 2018 paper published in the journal Respiratory Care, Napolitano found that clinicians who had administered HFNC to their pediatric patients had wide variations in how they set the flow rate. The paper concluded that more research is needed to define HFNC, determine how to set flow, and how to deliver medication.6 “High-flow [oxygen] therapy itself is a big grey zone and then you are adding delivery of aerosolized therapy onto it, so it is even more difficult to know whether or not it is effective,” said Napolitano.
Additionally, administering medication via HFNC is affected by many factors. The patient’s age, breathing patterns, and individual anatomy, may all impact the therapy. Differences in airway size, breathing and lung volumes can also impact the ability to deliver adequate aerosol doses to targeted parts of the lungs, according to Al-Subu.
The smaller airways common in children lead to higher rates of delivery and deposition of aerosol therapy in the upper respiratory tract, while in adults more medication is distributed in the lower respiratory tract, according to the study in Expert Review of Respiratory Medicine.7
Another issue that respiratory therapists may run into is that the higher the flow, the less effective the medication becomes. Aerosols delivered through HFNC are only effective at flows of 2 to 4 LPM, said Al-Subu.
“People may not be delivering the doses that they think they are delivering. The delivery of nebulized aerosol therapies is not as good with higher flows, said Al-Subu. “…Based on the literature that we did so far, I cannot have a strong recommendation for or against delivering aerosols with high flow nasal cannula.”
If aerosols are given through HFNC, clinicians should stay with the patient for three to five minutes to watch and make sure they are tolerating the flow and responding to the medication. “Observe the patient to make sure you are getting the result you are anticipating,” said Al-Subu.
Some clinicians “eyeball” the flow rate and medication amount while monitoring the patients to see how they respond. If high flows are needed, respiratory therapists at UAB Hospital in Birmingham, Alabama, adjust the dose to make up for the diminishing effect of the medication, said department manager Robert Johnson, RRT, MS.
“How do you know it is working? The same way you know on any other patient. For your asthmatic, your wheezing gets better. For your pulmonary hypertension, your saturation gets better. If it wasn’t working, those conditions wouldn’t get better.” RT
Lisa Spear is associate editor of RT. For more information contact [email protected]
- Madney YM, Fathy M, Elberry AA, Rabea H, Abdelrahim ME. Aerosol Delivery Through an Adult High-Flow Nasal Cannula Circuit Using Low-Flow Oxygen. Respiratory Care. 2019. doi:10.4187/respcare.06345.
- Tian G, Hindle M, Longest PW. Targeted lung delivery of nasally administered aerosols. Aerosol Sci Technol 2014;48(4):434-449.
- Réminiac F, Vecellio L, Loughlin RM, et al. Nasal high flow nebulization in infants and toddlers: An in vitro and in vivo scintigraphic study. Pediatric Pulmonology. 2016;52(3):337-344. doi:10.1002/ppul.23509.
- Lenglet H, Sztrymf B, Leroy C, Brun P, Dreyfuss D, Ricard JD. Humidified high flow nasal oxygen during respiratory failure in the emergency department: feasibility and efficacy. Respir Care. 2012;57(11):1873-8.
- Al-Subu AM, Hagen S, Eldridge M, Boriosi J. Aerosol therapy through high flow nasal cannula in pediatric patients. Expert Review of Respiratory Medicine. 2017:1-9. doi:10.1080/17476348.2017.1391095.
- Miller AG, Gentle MA, Tyler LM, Napolitano N. High-Flow Nasal Cannula in Pediatric Patients: A Survey of Clinical Practice. Respiratory Care. 2018;63(7):894-899. doi:10.4187/respcare.05961.
- Al-Subu AM, Hagen S, Eldridge M, Boriosi J. Aerosol therapy through high flow nasal cannula in pediatric patients. Expert Review of Respiratory Medicine. 2017:1-9.