Table 2.

Definition of criteria for acute hypoxemic respiratory failure and study treatment algorithm

Study	Criteria for acute hypoxemic respiratory failure	Study treatment algorithms
Antonelli et al. 2000 [10]	RR >35/min; PaO2/FiO2 < 200 while breathing oxygen; active contraction of accessory muscles of respiration or paradoxical abdominal motion	Ventilation algorithm: NIV via facemask; pressure support adjusted to obtain a Vt of 8–10 mL/kg, RR <25/min, the disappearance of accessory muscle activity and patient comfort. Control algorithm: patients received oxygen supplementation via a Venturi mask starting with an FiO2 ≥ 0.4, and adjusted to SpO2 > 90%
Hilbert et al. 2001 [11]	Pulmonary infiltrates and fever; severe dyspnea at rest; RR >30/min; PaO2/FiO2 < 200 while breathing oxygen	Ventilation algorithm: NIV via facemask; pressure support adjusted to obtain a Vt of 7–10 mL/kg; RR <25/min. PEEP was increased by 2 cmH2O, up to 10 cmH2O, adjusted to FiO2 ≤ 65% and SpO2 > 90%. Control algorithm: patients received oxygen through a Venturi mask. The rate of administration of oxygen was adjusted to SpO2 > 90%
Squadrone et al. 2010 [12]	Bilateral pulmonary infiltrates; SpO2 < 90% with room air; RR >25/min; respiratory symptom duration <48 h	Ventilation algorithm: CPAP via facemask or helmet at 10 cmH2O and FiO2 = 50%. Control algorithm: patients received oxygen through a Venturi mask
Wermke et al. 2012 [13]	RR >25/min; PaO2/FiO2 < 300 or SpO2 < 92% with room air	Ventilation algorithm: NIV via facemask; with pressure support of 15 cmH2O and an initial PEEP of 7 cmH2O; adjustments were according to capillary blood gas analysis and tolerance of patient. Control algorithm: patients received oxygen via nasal insufflation or full face mask initially set to 3 L/min. Adjustment of oxygen flow was left to physician’s discretion
Lemiale et al. 2015 [14]	PaO2 < 60 mmHg with room air; RR >30/min, or labored breathing or respiratory distress or dyspnea at rest; respiratory symptom duration <72 h	NIV algorithm: NIV via facemask; pressure support adjusted to obtain a Vt of 7–10 mL/kg ideal body weight; with an initial PEEP 2–10 cmH2O. The FiO2 and PEEP were adjusted to SpO2 ≥ 92%. Control algorithm: oxygenation modalities and the use of HFNC at clinician’s discretion

PaO ₂ /FiO ₂ ratio of arterial pressure of oxygen/fraction of inspired oxygen, SpO ₂ pulse arterial oxygen saturation, CPAP continuous positive airway pressure, HFNC heated and humidified high flow oxygen delivered by nasal cannula, ICU intensive care unit, PEEP positive end expiratory pressure, NIV noninvasive ventilation, RR respiratory rate, Vt tidal volume