Table 2 Gas exchange, inspiratory effort, dyspnoea, consciousness, and NPPV tolerance

Gas exchange

 pH

  Baseline

7.31 ± 0.07

7.33 ± 0.06

0.441

  2 h

7.37 ± 0.06

7.36 ± 0.06

0.603

  6 h

7.42 ± 0.06

7.39 ± 0.06

0.202

  24 h

7.48 ± 0.05

7.41 ± 0.05

0.002

  48 h

7.47 ± 0.04

7.41 ± 0.03

0.001

  72 h

7.47 ± 0.03

7.43 ± 0.04

0.013

 PaCO₂, mmHg

  Baseline

83.4 ± 12.3

78.6 ± 11.3

0.331

  2 h

70.6 ± 11.4

73.8 ± 8.6

0.445

  6 h

63.9 ± 13.6

71.2 ± 11.2

0.166

  24 h

54.0 ± 11.6

67.4 ± 10.6

0.008

  48 h

51.7 ± 10.6

66.7 ± 8.4

0.001

  72 h

50.6 ± 9.5

63.4 ± 8.9

0.003

 Difference in PaCO₂, mmHg

  Between baseline and 2 h

12.8 ± 7.4

4.8 ± 8.2

0.020

  Between baseline and 6 h

19.5 ± 9.9

7.4 ± 8.4

0.004

  Between baseline and 24 h

29.3 ± 12.2

11.2 ± 9.7

0.001

  Between baseline and 48 h

31.7 ± 9.7

11.9 ± 9.6

0.000

  Between baseline and 72 h

32.7 ± 10.2

15.2 ± 9.6

0.000

 PaO₂/FiO₂, mmHg

  Baseline

230 ± 63

240 ± 60

0.701

  2 h

247 ± 60

232 ± 60

0.549

  6 h

273 ± 71

253 ± 79

0.523

  24 h

300 ± 92

256 ± 60

0.187

  48 h

298 ± 66

257 ± 81

0.186

  72 h

306 ± 72

269 ± 58

0.179

 Bicarbonates, mmol/L

  Baseline

37.2 ± 7.6

37.2 ± 5.7

0.993

  2 h

37.4 ± 7.5

38.4 ± 6.4

0.715

  6 h

38.7 ± 7.7

39.1 ± 5.4

0.894

  24 h

38.4 ± 6.2

39.4 ± 5.3

0.670

  48 h

36.6 ± 5.3

38.6 ± 5.7

0.384

  72 h

35.7 ± 5.7

38.8 ± 4.7

0.156

 Inspiratory effort*

  ΔPes, cmH₂O

2.8 ± 2.2 (n = 11)

6.2 ± 4.5 (n = 11)

0.031

  PTPes/breath, cmH₂O·s

1.3 ± 1.3 (n = 11)

4.4 ± 2.2 (n = 11)

0.001

  PTPes/min, cmH₂O·s/min

20.1 ± 17.9 (n = 11)

83.3 ± 54.9 (n = 11)

0.003

  PTPes/L, cmH₂O·s/L

1.7 ± 1.4 (n = 11)

9.2 ± 5.8 (n = 11)

0.001

Dyspnoea, consciousness, and NPPV tolerance

 Accessory muscle use

  Baseline

4.0 (4.0–5.0)

4.0 (3.0–4.8)

0.387

  2 h

3.0 (2.0–3.0)

3.5 (3.0–4.0)

0.097

  6 h

2.0 (2.0–3.0)

3.0 (3.0–3.0)

0.008

  24 h

2.0 (1.0–2.0)

3.0 (2.0–3.0)

0.003

  48 h

1.0 (1.0–2.0)

2.0 (2.0–3.0)

0.004

  72 h

1.0 (1.0–2.0)

3.0 (2.0–2.8)

0.024

 Dyspnoea score

  Baseline

8.0 (7.3–10.0)

8.0 (6.0–8.0)

0.060

  2 h

5.0 (3.3–6.0)

6.0 (4.0–7.8)

0.306

  6 h

3.0 (2.0–5.5)

4.5 (3.3–6.0)

0.157

  24 h

1.0 (1.0–2.8)

3.5 (2.3–5.0)

0.004

  48 h

1.0 (0.0–2.0)

2.0 (2.0–3.8)

0.009

  72 h

1.0 (0.0–1.8)

2.0 (2.0–2.0)

0.001

 GCS score

  Baseline

14.0 (12.0–15.0)

15.0 (14.3–15.0)

0.092

  2 h

15.0 (15.0–15.0)

15.0 (15.0–15.0)

0.929

  6 h

15.0 (15.0–15.0)

15.0 (15.0–15.0)

 > 0.999

  24 h

15.0 (15.0–15.0)

15.0 (15.0–15.0)

0.317

  48 h

15.0 (15.0–15.0)

15.0 (15.0–15.0)

 > 0.999

  72 h

15.0 (15.0–15.0)

15.0 (15.0–15.0)

 > 0.999

 Kelly–Matthay score

  Baseline

3.0 (2.0–3.0)

2.0 (2.0–2.8)

0.178

  2 h

1.5 (1.0–2.0)

2.0 (1.0–2.0)

0.754

  6 h

1.0 (1.0–2.0)

1.5 (1.0–2.0)

0.514

  24 h

1.0 (1.0–1.0)

1.0 (1.0–2.0)

0.320

  48 h

1.0 (1.0–1.0)

1.0 (1.0–1.0)

0.546

  72 h

1.0 (1.0–1.0)

1.0 (1.0–1.0)

 > 0.999

 NPPV tolerance score

  Baseline

3.0 (2.3–4.0)

4.0 (3.0–4.0)

0.415

  2 h

3.5 (3.0–4.0)

4.0 (3.0–4.0)

 > 0.999

  6 h

4.0 (3.0–4.0)

4.0 (3.0–4.0)

0.741

  24 h

4.0 (3.0–4.0)

4.0 (3.0–4.0)

0.500

  48 h

4.0 (3.0–4.0)

4.0 (3.0–4.0)

0.741

  72 h

4.0 (3.3–4.0)

4.0 (3.0–4.0)

0.297