NIV was administered in both arms using the Servo-i ventilator (Maquet, Getinge Group, Solna, Sweden). We delivered NIV through an oronasal mask (UltraMirage, ResMed, Sydney, Australia) of appropriate size. Subjects were allowed intermittent periods off NIV for eating or expectoration of respiratory secretions. During such periods, they were given oxygen through nasal cannula, with a target S pO 2 of 89-92%. Subjects in both study groups received standard medical care (eg, enteral nutrition, deep venous thrombosis prophylaxis, stress ulcer prophylaxis) as per the existing ICU protocol, in addition to the treatment specific to the underlying clinical condition. We did not use sedation during NIV.
PSV Mode. Subjects randomized to PSV mode were ventilated with an initial pressure support of 6 cm H 2 O above PEEP, which was adjusted in steps of 2 cm H 2 O every 15 min to achieve a tidal volume of 6 mL/kg ideal body weight, breathing frequency < 30 breaths/min, and relief from dyspnea. PEEP was commenced at 5 cm H 2 O and was titrated along with F IO 2 to achieve the target S pO 2 of 89-92%. A minimum pressure difference of 4 cm H 2 O between pressure support and PEEP was always maintained. The maximum pressure support and PEEP allowed in the study were 20 cm H 2 O and 10 cm H 2 O, respectively.
PSV Mode. Subjects randomized to PSV mode were ventilated with an initial pressure support of 6 cm H 2 O above PEEP, which was adjusted in steps of 2 cm H 2 O every 15 min to achieve a tidal volume of 6 mL/kg ideal body weight, breathing frequency < 30 breaths/min, and relief from dyspnea. PEEP was commenced at 5 cm H 2 O and was titrated along with F IO 2 to achieve the target S pO 2 of 89-92%. A minimum pressure difference of 4 cm H 2 O between pressure support and PEEP was always maintained. The maximum pressure support and PEEP allowed in the study were 20 cm H 2 O and 10 cm H 2 O, respectively.