Table 1 Baseline characteristics on admission and before continuous positive airway pressure treatment

Demographics

   Male

143 (49)

36 (41)

0.167^a

   Age (years)

80 ± 10 (n = 290)

81 ± 9.5 (n = 88)

0.360^b

Comorbidities

   Chronic obstructive pulmonary disease

84 (29)

17/86 (20)

0.091^a

   Essential hypertension

162 (56)

46/86 (54)

0.697^a

   Diabetes mellitus

72 (25)

19/86 (22)

0.603^a

   Congestive heart failure

165 (57)

51/86 (59)

0.692^a

   Chronic renal failure

76 (26)

13/86 (15)

0.034^a

Severity of the disease

   Simplified Physiologic Acute Score II

42 ± 6.7 (n = 258)

40 ± 8.1 (n = 74)

0.014^b

Physical findings

   Systolic blood pressure (mmHg)

173 ± 30 (n = 286)

170 ± 31 (n = 87)

0.328^b

   Diastolic blood pressure (mmHg)

99 ± 20 (n = 283)

97 ± 19 (n = 87)

0.391^b

Systolic <140 mmHg and diastolic <90 mmHg

32 (11)

9 (10)

0.802^b

   Heart rate (beats/minute)

116 ± 22 (n = 283)

121 ± 22 (n = 87)

0.163^b

Heart rate >100 beats/minute

197/283 (70)

53/87 (61)

0.130^a

   Respiratory rate (breaths/minute)

41 ± 6.1 (n = 175)

39 ± 6.9 (n = 64)

0.016^b

Respiratory rate ≥40 breaths/minute

120/175 (69)

30/64 (47)

0.002^a

Arterial blood gas analysis

   pH

7.22 ± 0.09 (n = 290)

7.39 ± 0.03 (n = 88)

Not applicable

   PaCO₂ (mmHg)

53 ±16 (n = 290)

36 ±6.6 (n = 88)

<0.001^b

   Bicarbonates (mmol/l)

22 ± 5.3 (n = 288)

22 ± 3.8 (n = 88)

0.330^b

   PaO₂/FiO₂ ratio

178 ± 93 (n = 283)

222 ± 82 (n = 87)

<0.001^b

PaO₂/FiO₂ ratio <200

184/283 (65)

32/87 (37)

<0.001^a

Acute myocardial infarction on admission

43 (15)

14 (16)

0.804^a

CPAP setting

   Initial FiO₂ (%)

49.7 ± 12.1 (n = 288)

48.6 ± 11.4 (n = 88)

0.421^b

   Initial PEEP (cmH₂O)

9.7 ± 2.0 (n = 290)

9.7 ± 1.3 (n = 88)

0.927^b

   Device

Face mask

38 (19)

15 (24)

0.475^a

Helmet

157 (81)

48 (76)

Information not available

95

29