A Bench Comparison of the Effect of High-Flow Oxygen Devices on Work of Breathing

BACKGROUND: Oxygen therapy via high-flow nasal cannula (HFNC) has been extensively used during the COVID-19 pandemic. The number of devices has also increased. We conducted this study to answer the following questions: Do HFNC devices differ from the original device for work of breathing (WOB) and generated PEEP?

METHODS: Seven devices were tested on ASL 5000 lung model. Compliance was set to 40 mL/cm H₂O and resistance to 10 cm H₂O/L/s. The devices were connected to a manikin head via a nasal cannula with F_IO2 set at 0.21. The measurements were performed at baseline (manikin head free of nasal cannula) and then with the cannula and the device attached with oxygen flow set at 20, 40, and 60 L/min. WOB and PEEP were assessed at 3 simulated inspiratory efforts (−5, –10, –15 cm H₂O muscular pressure) and at 2 breathing frequencies (20 and 30 breaths/min). Data were expressed as median (first-third quartiles) and compared with nonparametric tests to the Optiflow device taken as reference.

RESULTS: Baseline WOB and PEEP were comparable between devices. Over all the conditions tested, WOB was 4.2 (1.0−9.4) J/min with the reference device, and the relative variations from it were 0, −3 (2–4), 1 (0–1), −2 (1–2), −1 (1–2), and −1 (1–2)% with Airvo 2, G5, HM80, T60, V500, and V60 Plus devices, respectively, (P < .05 Kruskal-Wallis test). PEEP was 0.9 (0.3–1.5) cm H₂O with Optiflow, and the relative differences were −28 (22–33), −41 (38–46), −30 (26–36), −31 (28–34), −37 (32–42), and −24 (21–34)% with Airvo 2, G5, HM80, T60, V500, and V60 Plus devices, respectively, (P < .05 Kruskal-Wallis test).

CONCLUSIONS: WOB was marginally higher and PEEP marginally lower with devices as compared to the reference device.