Table 2.
Multivariable risk factor model for lowest oxygen saturation
| Variable | Mean Difference in Predicted Lowest SpO2 (95% CI) | Adjusted P Value |
|---|---|---|
| Age, 67 yr vs. 47 yr | 3.0 (1.2 to 4.8) | 0.006 |
| Sex, female vs. male | −1.9 (−4.2 to 0.5) | 0.12 |
| Body mass index, 32.8 vs. 23.7 kg/m2 | −2.1 (−3.9 to −0.3) | 0.04 |
| Sepsis, present vs. absent | −1.0 (−3.5 to 1.4) | 0.42 |
| Operator experience, 85 vs. 40 intubations | 2.1 (0.3 to 3.8) | 0.04 |
| APACHE II score, 26 vs. 17 | 1.0 (−0.6 to 2.7) | 0.41 |
| Race | 0.02 | |
| Black vs. white | 4.1 (1.1 to 7.1) | |
| Other vs. white | −1.8 (−7.0 to 3.4) | |
| Indication for procedure | <0.001 | |
| Hypercapnia vs. neither | 7.6 (2.9 to 12.2) | |
| Hypoxemia vs. neither | −3.1 (−5.8 to −0.4) | |
| Noninvasive ventilation in preceding 6 h vs. none | −0.9 (−3.7 to 1.9) | 0.54 |
| Highest fraction inspired O2 in preceding 6 h, 80% vs. 30% | −1.7 (−4.6 to 1.2) | 0.28 |
| Arterial oxygen saturation at induction, 100% vs. 95% | 7.4 (4.4 to 10.4) | <0.001 |
Definition of abbreviations: APACHE II = Acute Physiology and Chronic Health Evaluation II; CI = confidence interval; SpO2 = arterial oxygen saturation as measured by continuous pulse oximetry.
The table displays the mean difference in predicted lowest oxygen saturation for each covariate for specified contrast. For continuous variables, the difference in lowest oxygen saturation is compared between the 75th and 25th percentiles. For example, the lowest oxygen saturation is predicted to be 3% higher for a 67-year-old patient compared with a 47-year-old patient, after adjusting for prespecified confounders. The P values are for the nested model comparison of the overall model, with removal of the covariate term from the model.