Baseline characteristics of the patients
| Helmet | Mask | p-value | |
|---|---|---|---|
| Subjects n | 39 | 41 | |
| Age years | 78.36±10.58 | 78.48±7.75 | 0.3980 |
| Kelly score | 2.28±1.21 | 2.19±1.23 | 0.7143 |
| SAPS II | 35.41±10.36 | 35.68±10.51 | 0.9494 |
| Dyspnoea score | 7.68±2.20 | 7.06±2.75 | 0.5200 |
| Charlson index | 3.49±1.60 | 3.49±1.88 | 0.7167 |
| Secretions | 1.78±0.95 | 2.10±1.04 | 0.1678 |
| Systolic blood pressure mmHg | 139.15±31.03 | 140.8±31.85 | 0.7419 |
| Diastolic blood pressure mmHg | 73.23±17.47 | 73.38±21.26 | 0.9293 |
| Heart rate beats per min | 98.08±17.58 | 98.02±20.27 | 0.8163 |
| Respiratory rate breaths per min | 30.82±8.10 | 32.88±8.75 | 0.2796 |
| Body temperature °C | 36.40±0.42 | 36.70±0.85 | 0.4687 |
| Arterial pH | 7.27±0.05 | 7.26±0.06 | 0.8250 |
| PaO2 mmHg | 70.84±31.05 | 68.95±39.97 | 0.2093 |
| PaCO2 mmHg | 72.58±14.87 | 74.45±15.25 | 0.5366 |
| HCO3- mmol·L-1 | 30.68±6.97 | 31.32±7.24 | 0.6273 |
| PaO2/FIO2 | 193.33±50.74 | 194.05±67.89 | 0.7167 |