NIV success NIV failure     Mean SD Mean SD p-value pH 7.23 0.12 7.23 0.13 0.94 PaO2 (kPa) 10.10 4.30 11.81 8.05 0.29 PaCO2 (kPa) 11.20 4.40 10.16 4.00 0.27 Lactic acid (mmol/L) 2.0 2.1 1.4 0.9 0.07 Base excess 5.2 8.4 2.3 7.9 0.06 HCO3- (mmol/L) 27.3 7.3 24.9 5.9 0.10 C-reactive protein (CRP) (mg/L) 79 91 138 113 0.02* White Blood cell Count (WBC) (109/L) 13.4 5.4 12.3 6.7 0.45 Oxygen saturation 0.89 0.10 0.89 0.08 0.72 Systolic blood pressure (mmHg) 131 36 120 26 0.11 Heart rate (min-1) 110 19 107 29 0.60 Respiratory rate (min-1) 27 8 30 9 0.06 Temperature (°C) 37.2 0.9 37.3 1.3 0.59 Glasgow Coma Scale score 13 3 13 2 0.40

Table 2: Comparison of patients treated solely with NIV (NIV success) and patients requiring invasive ventilation after NIV was attempted (NIV failure). P-value less than 0.05 is marked with *.