The Science Journal of the American Association for Respiratory Care

2012 OPEN FORUM Abstracts

CAN HIGH FLOW NASAL CANNULA BE DRIVEN BY A CPAP MACHINE? ANALYSIS OF PRESSURE AS RELATED TO FLOW USING FOUR TYPES OF NASAL CANNULAS.

Lisa Tyler, Richard Lin; Respiratory Care, Children’s Hospital of Philadelphia, Philadelphia, PA

Background: There is increasing interest in the use of nasal cannula type interfaces for non-invasive respiratory support in the pediatric population because they are more comfortable and better tolerated. With hospital use, these interfaces are typically connected to systems with prescribed flow, driven by a wall pressure source. However, they are sometimes connected to a flow/pressure generator such as a CPAP or BiPAP system or a ventilator. We wanted to understand the relationship between flow and pressure for different nasal cannula interfaces to evaluate whether connecting them to a flow/pressure generator was as effective as using a wall pressure source. Methods: A flowmeter connected to a wall pressure source was used to deliver gas flow to the four types of nasal cannula devices we evaluated. Flow rates were varied between 0-15 lpm. Pressures were measured upstream of each nasal cannula device using a Bio-teck DMP+ universal pressure meter. There was no downstream resistance at the end of the test device. The devices evaluated were the standard length Airlife™ pediatric nasal cannula by Carefusion, the Fisher and Paykel pediatric HFNC, the Vapotherm pediatric HFNC, and the infant size RAM cannula™ by Neotech. Results: As seen in the attached graph, the flow/pressure relationship was non-linear. The pressures required to drive prescribed flow rates were much higher with the standard length nasal cannula than the other devices and would not be achievable with a portable flow/pressure generator. The prescribed flows were achieved at the lowest pressures with the RAM cannula. Discussion: We demonstrated that the relationship between flow and pressure varied widely with the nasal cannula devices tested. With some of these devices, reasonable flows could be achieved with a portable CPAP/BiPAP sytem. Appreciating the different flow/pressure relationships of these interfaces should be considered when using them with alternative modes of flow generation. Of course, the benefit of flow from these interfaces will depend on how they fit into the patient using them. A fit with less leak may benefit the patient because of increased airway pressure instead of flow. More investigation must be done to further understand how these different nasal cannula interfaces have an effect in managing respiratory failure in pediatric patients. Sponsored Research - None