Synchrony

HFNC was delivered using an Optiflow nasal interface connected to the PT101AZ (Airvo2) humidifier (Fisher & Paykel Healthcare, Auckland, New Zealand). Therapy typically was initiated at a flow of 35 L/min, titrating flow upward if tolerated to 45–50 L/min, in order to maintain SaO₂ > 90% or according to specific clinical orders. In addition, all patients from the HFNC group answered a questionnaire about comfort and tolerability during the first 12 h of their admission to the ED.
NIV was initiated by bi-level positive airway pressure (BiPAP) in the spontaneous/timed mode (Synchrony, Respironics, Inc, Murrysville, Pennsylvania) supplied with an identical set of masks. Expiratory and inspiratory pressures were gradually increased to the maximum tolerated over 1 h, in order to maintain SaO₂ > 90%, or according to specific clinical orders.

Patients were ventilated using the pressure support ventilation (PSV) module of two ventilators (Neftis; Linde, Munich Germany or Synchrony; Philips Respironics, Andover MA, USA).
Inspiratory positive airway pressure (IPAP) was set as the maximum inspiration pressure value tolerated by patients, able to ensure an exhaled tidal volume of 6 mL/kg (measured body weight). Expiratory positive airway pressure (EPAP) between 2 and 8 cmH₂O was applied. A back up respiratory rate of 12 breaths/min was set. Oxygen was added to ventilator at a flow able to reach a target SaO₂≥ 90%. PSV was delivered using either nasal or full face mask based on patient comfort.