By Jonathan Lee
Respiratory complaints are a common occurrence in 911 calls involving children. But managing pediatric airways and respiratory distress present several unique challenges, especially relative to adult care. Paramedics tend to have lower levels of exposure to pediatric patients, and often lack confidence in their management. This is often compounded by inadequate access to pediatric versions of equipment, such as supraglottic airways and continuous positive airway pressure (CPAP). Finally, pediatric patients are notoriously sensitive to hypoxia.
Within the last several years, a new option for managing respiratory distress has emerged and is gaining popularity. Heated, humidified, nasal cannula oxygen (HHNC) is becoming an increasingly common form of therapy for respiratory distress in pediatrics.
A working knowledge of high-flow (as it is frequently referred to) is important for prehospital providers for a number of reasons. First, it may be seen in the emergency department as an escalation of care for their patients. Second, it may be applied prior to transfer to a tertiary pediatric center. Finally, as the technology and the research matures, it is possible that it may enter the world of prehospital care.
What is high-flow oxygen?
There are several commercially-available devices to deliver HHNC. They all share several common components, most importantly a humidifier capable of supplying 100 percent humidity, as well as a heating element, allowing the gas to be delivered at body temperature.
The patient is fitted with a special nasal cannula, larger than a traditional low-flow nasal cannula, that occupies 25 to 50 percent of the nares when fitted properly.
The delivery of gas can then be titrated to the patient’s condition. Oxygen concentrations can be easily adjusted to manage hypoxia, and the flow of gas can also be adjusted. Typically, starting around 1 L/Kg/min, it can increase to levels as high as 2.5L/Kg/min to improve both oxygenation and work of breathing.
How does high-flow oxygen work?
There have been several proposed mechanisms for the benefits seen in respiratory distress patients receiving HHNC.
Some of these benefits are directly related to the heat and humidity of the gas. For example, one important role of nasopharyngeal space and its lining is to condition outside air before it reaches the lungs. However, heating and humidifying air has a metabolic cost to the body. Providing the gas ‘pre-conditioned’ with heat and moisture reduces this metabolic cost. Furthermore, by preconditioning to 100 percent humidity and 37 degrees Celsius, HHNC avoids many of the negative effects on lung and mucosa that often accompany administering cold, dry oxygen [1].
There are also benefits directly related to gas flow. Preconditioning the air means that much higher flows, up to 2 L/Kg/min, are reasonable. This means a 10kg child generally tolerates flows of 20 LPM, much higher than used with traditional nasal cannula.
Higher flow rates decrease inspiratory resistance, which can decrease work of breathing. It also decreases functional dead space by ‘washing out’ the nasopharynx, leading to more efficiency with respirations [1].
HHNC does not increase airway pressure in the same way as CPAP. Simply by opening or closing the mouth, the patient can cause wide variations in these pressures. However, even with the mouth open, a patient with appropriately sized cannula may see improved oxygenation as a result of increased distending pressures [1].
What does the research say about high-flow oxygen?
While there is an increasing amount of research pertaining to the use of HHNC, it is difficult to appreciate a true consensus in the literature regarding its role. In general terms, it appears that it is more effective in managing respiratory distress than simply providing oxygen by mask.
However, research comparing HHNC to interventions such as non-invasive positive pressure ventilation (NIPPV) in children is mixed. It appears that in the mild to moderate respiratory distress patients, HHNC may produce outcomes similar to CPAP, however, HHNC failure was more likely in more severe cases or those with comorbidities [2,3].
Cochrane reviews have been conducted on the use of HHNC in both infants with bronchiolitis as well as children requiring respiratory support [4,5]. The authors concluded there was insufficient evidence to demonstrate efficacy in either patient group.
The role of high-flow oxygen in emergency medicine
The popularity of HHNC for children in both the emergency department and the pediatric wards is increasing as equipment and protocols become more available, and it has been used to aid in numerous forms of respiratory distress, such as bronchiolitis, asthma and pneumonia [4-6]. It is often used in an attempt to avoid intubation [7].
Another advantage is that children on HHNC can often be managed on the ward, avoiding the cost to transfer the patient to the pediatric intensive care unit [8].
Outside of the hospital, there have been reports of the successful use of HHNC during transport [9]. The idea of a relatively safe and well-tolerated form of prehospital respiratory support for children is appealing to anyone working in the 911 environment. However, the relatively high cost of the units means that this unlikely to happen without much stronger evidence supporting is efficacy.
Remember these key points on high-flow oxygen:
- Heated and humidified air allows higher flow rates to be tolerated by patients.
- HHNC may be better than oxygen by mask.
- HHNC is not better than CPAP or BIPAP.
- There is no consensus in the evidence surrounding the safety and efficacy of HHNC in children.
References
- Dysart, K., Miller, T.L., Wolfson,, M.R., and Shaffer, T.H. (2009). Research in high flow therapy: Mechanism of action. Respiratory Medicine, Vol 103(10), pages 1400-1405. https://doi.org/10.1016/j.rmed.2009.04.007
- Franklin, D., Babl, F.E., Schlapbach, L.J., Oakley, E., Craig, S., Neutze, J., Furyk, J., Fraser, J.F., Jones, M., Whitty, J.A., Dalziel, S.R., and Schibler, A. (2018). A randomized trial of high-flow oxygen therapy in infants with bronchiolitis. New England Journal of Medicine, 378: 1121-1131 DOI: 10.1056/NEJMoa1714855
- Betters, K. A., Gillespie, S. E., Miller, J. , Kotzbauer, D. and Hebbar, K. B. (2017), High flow nasal cannula use outside of the ICU; factors associated with failure. Pediatr Pulmonol., 52: 806-812. doi:10.1002/ppul.23626
- Beggs S, Wong ZH, Kaul S, Ogden KJ, Walters JAE. High-flow nasal cannula therapy for infants with bronchiolitis. Cochrane Database of Systematic Reviews 2014, Issue 1. Art. No.: CD009609. DOI: 10.1002/14651858.CD009609.pub2.
- Mayfield S, Jauncey-Cooke J, Hough JL, Schibler A, Gibbons K, Bogossian F. High-flow nasal cannula therapy for respiratory support in children. Cochrane Database of Systematic Reviews 2014, Issue 3. Art. No.: CD009850. DOI: 10.1002/14651858.CD009850.pub2.
- Riese, J., Porter, T., Fierce, J., Riese, A., Richardson, T., and Alverson, B.K. Clinical Outcomes of Bronchiolitis After Implementation of a General Ward High Flow Nasal Cannula Guideline
- Goh, C. T., Kirby, L. J., Schell, D. N. and Egan, J. R. (2017), Humidified high‐flow nasal cannula oxygen in bronchiolitis reduces need for invasive ventilation but not intensive care admission. J Paediatr Child Health, 53: 897-902. doi:10.1111/jpc.13564
- Collins, C., Chan, T., Robert, J.S., Haaland, W.L., and Wright, D.R. High-Flow Nasal Cannula in Bronchiolitis: Modeling the Economic Effects of a Ward-Based Protocol Hospital Pediatrics Aug 2017, 7 (8) 451-459; DOI: 10.1542/hpeds.2016-0167
- Schlapbach, Luregn & Schaefer, Jonas & Brady, Ann-Maree & Mayfield, Sara & Schibler, Andreas. (2014). High-flow nasal cannula (HFNC) support in interhospital transport of critically ill children. Intensive care medicine. 40. 10.1007/s00134-014-3226-7.
About the author
Jonathan Lee is a flight paramedic and an experienced educator with a special focus on pediatrics. After a number of different 911 and flight paramedic positions, Lee began working in a critical care environment in 2000 when he moved to Bandage One, the helicopter service located in Toronto. In 2010, he moved to his current position with the pediatric critical care transport team at Ornge.
Lee has a varied background in medical education which ranges from teaching initial paramedic education to the delivery of CME programs in the college, hospital and base-hospital setting. He takes pride in his instructional design experience including numerous projects in support of flight paramedics as well as extensive involvement in the development of an emergency nursing certificate program. Connect with him on Twitter @thatjonlee.