Device Response to Flow and Obstruction via High Flow Nasal Cannula

Abstract

Background:

High-flow nasal cannula (HFNC) is a therapy that can be applied by many devices. Healthcare institutions may have several different devices that deliver HFNC. These devices may vary due to the interaction of flows, nasal cannula (NC) sizes, and obstruction. The aim of this comparative bench study was to evaluate the response of HFNC devices with predetermined flows, NC sizes, and obstruction.

Methods:

Three aerosol T-pieces with two holes drilled at diameters twice the size of the prong inner diameters were used to simulate small, medium, and large nares. The Fisher & Paykel Optiflow small, medium, and large NC were used. The prongs occupied up to 50% of the corresponding simulated nares. The devices tested were a blender set-up, Hamilton T-1 (HT), Dräger V500 (DV), Respironics V60 (RV), and Fisher & Paykel Airvo 2 (FP). An Ingmar Medical ASL-5000 simulated mild adult respiratory distress. The HFNC devices were tested with each size NC attached to its corresponding aerosol T-piece and the ASL. The device flow was started at 10 L/min and increased by 10 L/min to the device maximum flow (DM). Device response was recorded. The devices were tested again with one prong of the NC clamped to simulate an obstruction. The flow was started at DM and decreased in increments of 10 L/min.

Results:

The blender set-up delivered flow with any NC size and obstruction up to a DM of 70 L/min. It does not have alarms. HT and DV alarmed and flow stopped when the flow was obstructed. RV and FP alarmed and delivered a lower flow than the set flow when the flow was obstructed. Without obstruction, HT and DV can deliver DM (60 L/min; 50 L/min) with any NC size. Without obstruction RV and FP can deliver DM (80 L/min; 60 L/min) with the medium and large NC; and a 50 L/min flow limit with the small NC. With obstruction, HT and DV can deliver DM with medium and large NC. HT and DV are limited to 40 L/min with an obstructed small NC. With obstruction, RV can deliver 60 L/min with the medium and large NC, and 40 L/min with the small NC. FP with obstruction can deliver DM with the large, 50 L/min with the medium, and 30 L/min with the small NC.

Conclusions:

Devices that deliver HFNC respond differently depending on the interaction of the nasal NC size, flow, and obstruction of flow. Bedside clinicians should be aware of flow limitation and the device response. This information may be used clinically as part of a device troubleshooting algorithm, and to determine how an obstruction may affect patients.