Table 1 Baseline patient characteristics

High-flow nasal cannula group (n = 158)

Conventional oxygen therapy group (n = 172)

Characteristics of the patients at admission

Age, median (IQR), y

70.0(65.0–75.0)

69.0(63.5–74.5)

Men, No. (%)

140(88.6%)

137(79.7%)

Body mass index*, median (IQR), kg/m²

21.0(18.7–23.3)

21.0(18.7–23.3)

APACHE II score, median (IQR)

10.0(7.0–13.0)

10.0(7.0–13.5)

Symptoms at admission, No. (%)

Dyspnoea

149(94.3%)

170(98.8%)

Cough

143(90.5%)

157(91.3%)

Wheeze

118(74.4)

138(80.2%)

Sputum production

101(63.9%)

91(52.9%)

Fever

24(15.2%)

24(14%)

Comorbidities, No. (%)

Hypertension

54(34.2%)

65(37.8%)

Diabetes mellitus

16(10.1%)

13(7.6%)

Asthma

11(7.0%)

8(4.7%)

Chronic heart failure

7(4.4%)

12(7.0%)

Bronchiectasis

7(4.4%)

10(5.8%)

Current smoker, No. (%)

34(21.5%)

35(20.3%)

FEV1% predicted, No

59

67

Median (IQR)

32.5(24.8–42.1)

32.0(24.6–43.1)

FEV1/FVC% predicted, No

60

67

Median (IQR)

41.6(33.0–51.3)

42.6(34.6–51.6)

Prior use of long-term oxygen therapy, No. (%)

37(23.4%)

40(23.3%)

Physiological characteristics at randomization

Body temperature, median (IQR), °C

36.5(36.4–36.8)

36.6(36.4–36.8)

Respiratory rate, median (IQR), breaths/min

21.0(20.0–23.0)

21.0(20.0–23.0)

Heart rate, median (IQR), beats/min

85.0(78.0–98.0)

88.5(78.5–100.0)

Mean blood pressure, median (IQR), mmHg

95.0(87.3–102.7)

96.0(88.7–102.8)

SpO₂, median (IQR), %

93.0(89.0–96.0)

92.0(88.0–96.0)

Nasal cannula, No. (%)

89(56.3%)

98(57.0%)

O₂ flow, median (IQR), L/min

2.0(2.0–3.0)

2.0(2.0–3.0)

Borg scale score, median (IQR), units

4.0(3.0–5.0)

4.0(3.0–5.0)

pH, median (IQR), units

7.40(7.37–7.42)

7.40(7.37–7.43)

PaCO₂, median (IQR), mmHg

50.4(47.3–56.3)

51.7(47.6–58.0)

PaO₂, median (IQR), mmHg

70.4(57.0–83.0)

68.0(56.0–83.7)

Bicarbonate, median (IQR), mmol/L

31.3(28.3–34.9)

31.8(29.0–35.2)

White blood cell, median (IQR), × 10⁹/L

6.9(5.5–9.4)

6.9(5.8–8.8)

C-reactive protein, median (IQR), mg/L

10.0(3.9–29.1)

8.7(4.1–30.9)