Combined data from both audits highlighting the mortality rate in acidotic versus non-acidotic patients, according to time to NIV
| Time to NIV | Mortality rate in patients acidotic on admission | Mortality rate of patients non-acidotic on admission | P value |
| <60 min | 68/414=16.4% | 4/56=7.1% | 0.092 |
| 60–179 min | 69/448=15.4% | 8/55=14.5% | 0.068 |
| 3–24 hours | 94/510=18.4% | 44/231=19% | 0.842 |
| >24 hours | 39/135=28.9% | 103/242=42.6% | 0.009 |
| Overall Mortality (regardless of time to NIV) | 318/1770=18.0% | 172/699=24.6% | <0.001 |
| Median hours between first and second ABG | 1.8 | 5.6 | <0.001 |
| Median hours from second ABG to NIV | 0.22 | 2 | <0.001 |
ABG, arterial blood gas; NIV, non-invasive ventilation.