Table 1 Clinical and demographic characteristics

Age in years, median (IQR)

55 (45–63)

61(51–67)

0.115

Male, n (%)

62 (61)

15 (39)

0.019

BMI, kg/m², median (IQR)

28 (25–32)

28 (26–31)

0.586

Days of symptoms upon admission, median (IQR)

8 (6–10)

8 (7–10)

0.920

APACHE II, median (IQR)

8 (7–10)

11 (8–13)

0.035

SOFA, median (IQR)

4 (3–4)

5 (4–5)

< 0.001

NEWS II, median (IQR)

11 (9–13)

11 (10–13)

0.110

LUS at admission, points, median (IQR)

21 (19–25)

26 (25–27)

< 0.001

PaO₂/FiO₂ ratio (mmHg), at admission, median (IQR)

106 (95–137)

95 (79–105)

0.012

Comorbidities

Diabetes, n (%)

5 (5)

0 (0)

1.000

Hypertension, n (%)

10 (9)

2 (1)

0.851

Asthma, n (%)

2 (2)

0 (0)

1.000

COPD, n (%)

1 (1)

0 (0)

1.000

Congestive heart failure, n (%)

3 (3)

2 (1)

0.158

Non-Invasive Respiratory Support

High-Flow Nasal Cannula, n (%)

57 (66)

4 (26)

N/A

Switched to CPAP, n (%)

29 (33)

11 (73)

N/A

ROXi at 2-h, median (IQR)

8.04 (7.52–10.35)

8.03 (5.62–10.14)

0.538

ROXi at 6-h, median (IQR)

8.90 (7.08–10.66)

9.12 (6.60–10.70)

0.789

ROXi at 12-h, median (IQR)

9.30 (7.62–11.35)

7.75 (6.12-10.00)

0.029

ROXi at 24-h, median (IQR)

10.26 (8.17–14.29)

6.96 (5.78-9.00)

< 0.001

ROXi at 48-h, median (IQR)

10.26 (8.17–14.29)

4.43 (3.70–5.55)

< 0.001

Laboratory test

D-Dimer, (µg/L), median (IQR)

348 (259–650)

390 (315–587)

0.497

C-Reactive Protein, (mg/L), median (IQR)

11 (6–15)

9 (6–19)

0.882

Ferritin, (µg/L), median (IQR)

819 (455–1363)

1182 (745–1500)

0.231

pH, median (IQR)

7.41 (7.40–7.44)

7,42 (7.41–7.43)

0.604

PaCO₂ mmHg, median (IQR)

35 (32–37)

35 (34–38)

0.591

PaO₂, mmHg, median (IQR)

85 (76–107)

72 (62–84)

0.014

HCO₃ meq/l, median (IQR)

22 (21–24)

23 (21–24)

0.837