Table 4 Primary and Secondary Indicators of Noninvasive Respiratory (NIRS) failure

Primary Indicators of Noninvasive Respiratory Support Failure

1) PaO₂/FiO₂ < 150 or inability to improve PaO₂/FiO₂ after 1 h of NIV [39, 50, 55]

2) Worsening/unimproved dyspnea or tachypnea > 25 after 1 h of NIV [24, 39, 53, 56]

3) Failure to maintain PaO₂ of 60 on FiO₂ of 0.6 [39, 53]

4) SpO₂/FiO₂ < 196 [35]

5) Tidal volume of > 9 ml/kg predicted body weight [21, 43, 54]

6) ROX value less than 2.85 at 2 h, less than 3.47 at 6 h, or less than 3.85 at 12 h predict HFNC failure [57]

7) pH < 7.25 or PaCO₂ > 75 after 2 h of NIV [42]

Secondary Indicators of Noninvasive Respiratory Support Failure

1) SAPS II > 35, APACHE II > 17, or rising SOFA score [39, 51, 52, 55]

2) High peak pressure requirement [39, 53]

3) Worsening bronchorrhea [39, 53]

4) Intolerance of mask [39, 53]