Hygrometry of gas delivered with different high flow oxygen humidifiers and impact on comfort of the level of hygrometry

Methods We have tested on a bench the hygrometric performance of different oxygen high flow therapy systems (OptiFlow/ Airvo Fisher&Paykel, Hydrate OMNI Hydrate inc., Precision flow Vapoterm,). We have used psychrometric method to measure hygrometry. For each condition, we made 3 hygrometric measurements at different moments of the day. The measurements were taken proximal to the simulated patient’s interface. We have tested different settings (intubation and NIV settings for the Optiflow), different flow rates (10, 20-30-40 and 60l/min) and two ambient temperatures: normal temperature (22-24°C) and high temperature (28-30°C). We evaluated the comfort in 10 healthy subjects blinded for different humidity levels (20, 30 and 40 mgH2O/L) during 10 minutes in random orders.