The Science Journal of the American Association for Respiratory Care

2006 OPEN FORUM Abstracts

Comparison of High Flow Nasal Cannula (HFNC) Devices

*Brian K. Walsh, RRT-NPS, RPFT, ^Douglas Petsinger, RRT-NPS, tEric Hurd, RRT

* University of Virginia Children 's Hospital, ^Children's Healthcare of Atlanta,t Georgetown University

Background: The concept of high flow and high humidity via a nasal cannula (HFNC) was first introduced by Vapotherm to the respiratory care market in the spring of 2002 after receiving FDA approval. This introduction lead to the development of HFNC strategies that has proven to be an acceptable intensive care modality for rescue from endo-tracheal intubation, bridging from endo-tracheal mechanical ventilation, and long term supportive care of the growing neonate. Initially, the Vapotherm Nasal Cannula System (Vapotherm, Stevensville , MD , USA ) was the first widely used high flow NC system until several reports of restonia infection were reported by various hospitals. In December 22nd, 2005 Vapotherm voluntary recalled their device. The HFNC strategy has continued as a viable practice with other humidification devices. However, concerns with these new devices are: comparison humidification output, and alarms.

Method:
We compared the humidity and safety features of three devices. Humidification was sampled using a high performance digital thermo-hygrometer (Omega Engineering, Stamford , CT ) at the distal end of the delivery circuit. The baseline room temp was 22o C with a RH of 12%. Each of the devices was set-up according to manufacture recommendations with the exception of the Fisher Paykel (F&P East Tamaki, New Zealand ). This device was set-up according to common practice described on the AARC Neonatal Pediatric list serve from March 16th-27th. The F&P temperature setting was set on invasive and the pop-off was removed to achieve higher flows (off label use) in order to do a direct comparison. Oxygen flow from 1-8 l/min was sent through the Infant Continuous Low Flow Circuit by F&P and the Low Flow cartridge and circuit by Vapotherm. Oxygen flow of 15-35 l/min was sent through the Aquanox HF Humidification System (Smiths Medical, Kent UK) and High Flow cartridge by Vapotherm. In all cases the temperature and humidity output was monitored for 30 minutes and recorded in 5 minute increments. Safety features and alarms of each of the devices were tested. Common clinical events were replicated in the lab setting. The delivery tube was occluded, the oxygen source was disconnected and then reconnected after 5 minutes, and humidifier water supply and reservoir was depleted on each of the devices.
Results: Humidity-There was a statistical difference in the RH% between the F&P and Vapotherm devices (t-test p=0.015). There was no statistical difference in RH% of the Vapotherm and Aquanox systems (rank sum p=0.667). Safety-Two out of the three devices have heater alarms that function appropriately. When the delivery tubing was deliberately occluded, the F&P device has a silent pop-off, the Vapotherm has an audible electronic and manual pop-off valve, the AquinOx has a single pop-off sound and the circuit has to be manually put back together. When the source gas was deliberately disconnected, the Vapotherm device would alarm immediately, the F&P device had a delayed alarm up to 8-15 minutes later depending on flow rate. None of the devices over shot the baseline temperature when disconnected and reconnected after 5 minutes. Only the Vapotherm and F&P devices alarmed in low water states. See Figure 1.

Figure 1              Flow Settings liters/minute Setting Average RH% Heater Alarms Disconnect Alarm Auditable Pop-off Alarm
Device
Vapotherm 1-8 37 98.75% ü ü ü
F&P 1-8 Invasive 95.75% ü    
AquinOx 15-35 Max 98.5%     ü
Vapotherm 15-35 37 98% ü ü ü

Conclusion: Vapotherm in the 1-8 liter/minute delivered the highest RH%. There was no difference in RH% between the AquinOx and Vapotherm systems with flows >15 L/min. Vapotherm has the most safety features of all three devices which could possibly prevent adverse events.

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