Airvo2 device

A 5-cm H₂O/L/s resistor (Michigan Instruments, Grand Rapids, MI, USA) was connected to the expiratory port of an HFT interface (OPT870, Fisher & Paykel Healthcare, Auchland, New Zealand) (Fig. 1). During the study, HFT was delivered via the standard or modified interface using an AIRVO 2 device (Fisher & Paykel Healthcare, Auchland, New Zealand) and the manufacturer’s standard assembly composed of a heated breathing circuit and an auto-fill humidification chamber (900PT501, Fisher & Paykel Healthcare, Auchland, New Zealand).Figure 1

Standard and modified high-flow tracheal interface. (A) standard high-flow tracheal oxygen therapy interface; (B) test lung resistor (5 cm H₂O/L/s); (C) modified interface by connecting the resistor to the expiratory port of the standard interface.

HFNC was provided with one of the following devices: Optiflow device (MR850 heated humidified delivery tubing and nasal cannula; Fisher & Paykel Healthcare, Auckland, New Zealand)^™, Bio-med device high flow air-oxygen blender with the heated humidifier (MR850, Fisher & Paykel Healthcare, Auckland, New Zealand)^™ or the Airvo 2 device (Fisher & Paykel Healthcare, Auckland, New Zealand)^™. Despite the different devices, all the nasal cannula interfaces were similar to the Airvo2 device, where the nasal cannula is able to deliver humidified respiratory gases up to flows of 70L/min. Physicians initiated HFNC at a minimum flow of 30L/min with FiO₂ of at least 30% to target a SpO₂ of at least 92%.