TABLE 1

Baseline characteristics, continuous positive airway pressure (CPAP) treatment and outcomes of the study population according to CPAP failure or success

CPAP successCPAP failurep-value
Subjects n8770
Demographics
 Males60 (69.0)57 (81.4)0.08
 Age years66 (56–75)60 (51–72)0.08
  >65 years45 (51.7)26 (27.1)0.07
  >75 years20 (23.0)15 (21.4)0.82
 BMI27.4 (25.1–30.2)27.5 (23.7–29.3)0.39
 Obesity (BMI ≥30 kg·m−2)16 (25.4)13 (24.1)0.87
 Current/former smoker17 (19.5)10 (14.3)0.39
Comorbidities
 Any cardiovascular disease49 (56.3)32 (45.7)0.19
 Hypertension41 (47.1)28 (40.0)0.37
 Diabetes24 (27.6)12 (17.1)0.12
 Ischaemic cardiac disease19 (21.8)8 (11.4)0.09
 Chronic arrhythmia7 (8.1)10 (14.3)0.21
 Cerebrovascular disease9 (10.3)4 (5.7)0.39
 Immunosuppression8 (9.2)3 (4.3)0.35
 COPD7 (8.1)3 (4.3)0.51
 Chronic renal failure6 (6.9)3 (4.3)0.73
 Liver disease5 (5.8)4 (5.7)1.00
 Asthma1 (1.292 (2.9)0.59
Radiology
 Consolidation on chest radiograph66 (75.9)58 (82.3)0.29
 Pleural effusion15 (17.2)11 (15.7)0.80
Pharmacological treatment
 Treatment with immunomodulators
  None56 (64.4)42 (60.0)0.74
  Anakinra26 (29.9)22 (31.4)
  Tocilizumab5 (5.8)6 (8.6)
 Hydroxychloroquine84 (96.6)68 (97.1)0.83
 Lopinavir/ritonavir48 (55.2)37 (52.9)0.77
 Remdesivir2 (2.3)3 (4.3)0.66
 Endovenous steroids37 (42.5)35 (50.0)0.42
 Antibiotics84 (96.6)66 (94.3)0.49
 Anticoagulation24 (27.9)21 (30.4)0.73
Disease severity
 Severe pneumonia56 (64.4)55 (78.6)0.05
 Septic shock vasopressor3 (3.5)2 (2.9)1.00
 Aggressive fluid resuscitation2 (2.3)0 (0.0)0.50
Clinical variables before CPAP treatment
 Confusion7 (8.1)2 (2.9)0.30
 Temperature C (n=153)37.3±1.137.6±0.90.12
 Systolic blood pressure mmHg (n=156)130 (115–140)130 (120–140)0.87
 Diastolic blood pressure mmHg (n=156)75 (70–85)80 (70–85)0.69
 Heart rate bpm (n=156)88.3±15.686.5±14.50.47
 Respiratory rate breaths·min−1 (n=153)28 (24–32)25.5 (21–30)0.09
  Respiratory rate ≥30 breaths·min−137 (43.5)20 (29.4)0.07
SpO2% (n=154)93 (89–97)95.5 (90–97)0.41
Blood gas analysis before CPAP treatment
 pH (n=155)7.48 (7.45–7.51)7.47 (7.45–7.50)0.91
PaCO2 mmHg (n=157)33.0±5.032.9±5.90.89
PaO2 mmHg (n=157)65 (53–83)75.5 (60–96)0.009
PaO2:FIO2 ratio (n=157)136 (95.0–204.8)152 (100–202)0.85
PaO2:FIO2 ratio classes
   PaO2:FIO2 ratio ≤100 mmHg23 (26.4)18 (25.7)0.90
  100 mmHg <PaO2:FIO2 ratio ≤200 mmHg39 (44.8)34 (48.6)
  200 mmHg <PaO2:FIO2 ratio ≤300 mmHg25 (28.7)18 (25.7)
Blood tests before CPAP treatment
 White blood cells cell·mm−3 (n=156)7060 (5550–9630)8000 (5490–10 4500.45
 Platelets cell·mm−3 (n=155)227 00 (169 000–336 000)199 000 (142 000–264 500)0.02
 D-dimer µg·L−1 (n=126)793 (561.0–1242.5)1098 (667–2444)0.03
 Ferritin µg·L−1 (n=123)1484 (832–2732)1558.5 (1049–2830)0.54
 IL-6 ng·L−1 (n=125)46.6 (19–75)134 (77.9–266)<0.0001
 C-reactive protein, mg·dL−1 (n=157)13.6 (8.4–44.0)15.6 (10.8–25.8)0.49
CPAP initiation and treatment
FIO2 % (n=154)50 (50–60)60 (50–70)<0.0001
 PEEP cmH2O (n=154)10.4±2.211.4±2.40.01
 Increase of PaO2:FIO2 ratio of at least 20% from oxygen therapy to CPAP53 (64.6)33 (48.5)0.047
 Increase of PaO2:FIO2 ratio of at least 30% from oxygen therapy to CPAP51 (62.2)27 (39.7)0.006
 Days of CPAP treatment (n=153)8 (5–14)4 (3–7)<0.0001
CPAP complications
 Pneumothorax0 (0.0)1 (1.4)0.45
 Pneumomediastinum0 (0.0)2 (2.9)0.20
 Haemodynamic instability0 (0.0)9 (12.9)0.001
 Intolerance#10 (11.5)11 (15.7)0.44
 Ulcer2 (2.3)0 (0.0)0.50
Study outcomes
 Weaning from CPAP to oxygen therapy84 (96.6)6 (8.6)<0.0001
 Days from CPAP initiation to weaning to oxygen therapy (n=87)7 (4–12)7 (1–8)0.31
 Intubation0 (0.0)34 (48.6)<0.0001
 Days from CPAP initiation to intubation (n=34)3 (2–5)
 Mortality in HDU0 (0.0)36 (51.4)<0.0001
 Days from CPAP initiation to HDU mortality (n=36)5 (3–10)
 Length of hospitalisation (n=138)18 (14–25.5)8 (4–22)<0.0001
 In-hospital mortality0 (0.0)45 (64.3)<0.0001
 Days from CPAP initiation to in-hospital mortality (n=45)0 (0–0)6 (4–11)

Data are presented as n (%), median (interquartile range), mean±sd, unless otherwise stated. BMI: body mass index; bpm: beats per minute; SpO2: oxygen saturation measured by pulse oximetry; PaCO2: arterial carbon dioxide tension; PaO2: arterial oxygen tension; FIO2: inspiratory oxygen fraction; IL: interleukin; PEEP: positive end-expiratory pressure; HDU: high dependency unit. #: among them, four patients discontinued helmet CPAP.