Results of univariate and multivariate Cox proportional-hazards models relating parameters of the timed walk test and pulmonary function to mortality
| Variables | Univariate models | Multivariate# models | ||
| Relative hazard (95% CI) | p-value | Relative hazard (95% CI) | p-value | |
| Resting room air SP,O2 | 0.93 (0.75–1.14) | 0.454 | 1.06 (0.83–1.37) | 0.637 |
| End-exercise SP,O2 2% units | 0.73 (0.59–0.91) | 0.004 | 0.74 (0.55–1.00) | 0.051 |
| Change in SP,O2 with exercise¶ | 0.80 (0.69–0.92) | 0.002 | 0.80 (0.67–0.96) | 0.014 |
| Walk distance 30-m units | 0.89 (0.81–0.97) | 0.010 | 0.91 (0.81–1.02) | 0.098 |
| Walk velocity 0.1-m·s−1 units | 0.77 (0.65–0.91) | 0.002 | 0.76 (0.63–0.93) | 0.006 |
| DL,CO % pred | 0.93 (0.88–0.97) | 0.001 | 0.92 (0.87–0.98) | 0.005 |
| FVC % pred+ | 1.00 (0.97–1.02) | 0.781 | 0.94 (0.97–1.02) | 0.646 |
| Resting Pa,O2 mmHg | 0.97 (0.94–1.00) | 0.076 | 0.96 (0.91–1.01) | 0.101 |
| Resting PA–a,O2 difference mmHg | 1.01 (0.99–1.04) | 0.328 | 1.01 (0.97–1.05) | 0.672 |
CI: confidence interval; SP,O2: arterial oxygen saturation measured by pulse oximetry; DL,CO: diffusing capacity for carbon monoxide; % pred: % predicted; FVC: forced vital capacity; Pa,O2: arterial oxygen tension; PA–a,O2: alveolar–arterial oxygen tension. #: the multivariate model included age, sex, FVC % pred, time from the onset of symptoms and supplemental oxygen administration during the test; ¶: for consistency, change in saturation was entered as a negative change such that a lesser degree of desaturation would be associated with reduced mortality; +: the multivariate model excluded FVC as a covariate. 1 kPa = 0.133 mmHg.