Table 1 Univariate analysis of patient characteristics in intubated and nonintubated subjects

 Age, years

39 (32–51)

35 (29.25–40.5)

46 (36.25–55.75)

0.0005

 Male gender

64 (63%)

28 (56%)

36 (70.6%)

0.04

 Tobacco smokers

52 (51%)

29 (58%)

23 (45.1%)

0.23

 Any comorbidity

91 (89%)

41 (82%)

49 (96%)

0.03

 Hypertension

14 (14%)

3 (6%)

11 (21.6%)

0.04

 Cardiovascular disease

8 (8%)

3 (6%)

5 (9.8%)

0.72

 Diabetes

7 (7%)

3 (6%)

4 (7.8%)

1

 Chronic kidney disease

7 (7%)

2 (4%)

5 (9.8%)

0.44

 Chronic respiratory insufficiency

6 (6%)

2 (4%)

3 (5.9%)

1

 Other^b

5 (5%)

1 (2%)

3 (5.9%)

0.62

Underlying IS

53 (52%)

18 (36%)

35 (68.6%)

0.001

 Solid organ transplantation

11 (11%)

5 (10%)

6 (11.8%)

1

 Solid malignancy

7 (7%)

1 (2%)

6 (11.8%)

0.11

 Hematological malignancy

15 (15%)

4 (8%)

11 (21.6%)

0.09

 Pregnancy

6 (6%)

4 (8%)

2 (3.9%)

0.44

 Steroids treatment

22 (22%)

7 (14%)

15 (29.4%)

0.09

 Other immunosuppression^c

6 (6%)

1 (2%)

5 (9.8%)

0.20

 Respiratory rate, breaths/min

30 (24.5–35)

25 (22–30)

31 (28.25–39.75)

0.0006

 Oxygen flow, L/min

6 (3–15)

4 (2–8)

15 (9.75–15)

<0.0001

 PaO₂:FiO₂ ratio, mmHg

150 (80–284)

250 (126.5–331)

90 (72–162)

<0.0001

 Alveolar consolidation on chest X-ray

30 (33%)

9 (20%)

21 (46.7%)

0.01

 SOFA score at day 1

4 (3–7)

3 (2–4)

7 (5–10)

<0.0001

 Time (days) from dyspnea onset to ICU admission

2 (1–3)

2 (1–3)

1 (1–3)

0.34

Empirical antibiotics at ICU

62 (61%)

19 (38%)

42 (84%)

<0.0001

Early-documented bacterial co-infection

20 (20%)

4 (8%)

16 (31%)

0.005

Hospital mortality

24 (24%)

2 (4%)

22 (43%)

<0.0001