Linear regression analysis using the best independent correlates of BE from each domain
| Correlation coefficient | p Value | |
|---|---|---|
| Best independent correlates from each domain | ||
| Obesity | ||
| Visceral adipose tissue volume by DXA scan | +0.50 | 0.001 |
| Lung function | ||
| FEV1%, supine | −0.40 | <0.001 |
| Sleep variables | ||
| Mean overnight oxygen saturation | −0.50 | <0.001 |
| Ventilatory control | ||
| Ventilatory response to 15% oxygen | −0.28 | 0.02 |
| Respiratory muscle strength | ||
| Sniff maximum (cm H2O) | −0.28 | 0.02 |
| Hormonal, nutritional and inflammatory measures | ||
| Vitamin D | −0.30 | 0.01 |
| Cumulative correlation coefficient | p Value | |
| Significant independent correlates | ||
| Visceral adipose tissue volume by DXA scan | +0.49 | 0.004 |
| Ventilatory response to 15% oxygen | +0.58 | 0.04 |
Results for the best correlates of BE in a linear regression for each individual domain. The correlate was chosen on the basis of the likelihood of it having a causal association with BE (eg, ventilatory response to 15% oxygen was chosen over the absolute fall in SaO2, and vitamin D was chosen over both BNP and transferrin). The lower part of the table shows the result for the best overall significant independent correlates of BE in a multiple linear regression containing the best correlate from each domain. A cumulative correlation coefficient of 0.58 indicates that the model accounts for 34% of the variance in BE. Vitamin D levels were the next most significant correlate, but with a p value of 0.19.
BE, base excess; BNP, brain natriuretic peptide; DXA, dual-energy X-ray absorptiometry; FEV1, forced expiratory volume in 1 s.