Table 1 Demographics and baseline characteristics of enrolled patients

Age, years

72 [64–77]

Female sex , no. (%)

7 (35%)

Height, cm

168 [161–170]

Body mass index, kg/m²

28 [24–29]

Ideal body weight, kg

64 [57–66]

SAPS II

43 [34–51]

SOFA at study inclusion

4 [3–8]

Reason for ICU admission, no. (%)

 Medical

20 (100%)

 Surgical

0 (0%)

Cause of respiratory failure, no. (%)

 Pulmonary, infectious

13 (65%)

 Pulmonary, non-infectious

5 (25%)

 Extrapulmonary

2 (10%)

Length of noninvasive respiratory support before enrollment, hours

0 [0–14]

Baseline respiratory support device at enrollment, no. (%)

 Venturi mask

1 (5%)

 High-flow nasal oxygen

16 (80%)

 Facemask noninvasive ventilation

1 (5%)

 Helmet noninvasive ventilation

2 (10%)

Characteristics at enrollment

 PaO₂/FiO₂ ratio, mmHg

169 [112–279]

 PaCO₂, mmHg

33 [29–35]

 pH

7.45 [7.41–7.50]

 Heart rate, bpm

91 [81–109]

 Mean arterial pressure, mmHg

93 [84–103]

Room temperature, °C

25 [24, 25]

Room absolute humidity, mgH₂O/L

11 [9–12]

Room relative humidity, %

50 [41–52]

Sedation/analgesia during the study*, no. (%)

3 (15%)

Glasgow coma scale at study inclusion

15 [15–15]

Need for endotracheal intubation, no. (%)

9 (45%)

In-intensive care unit mortality, no. (%)

7 (35%)