Table 2.
Baseline participant characteristics by oxygen prescription group.
| Continuous (24-hour; N=214) | Intermittent (during exercise and sleep; N=145) | P* | |
|---|---|---|---|
| Demographics | |||
| Age (years; mean ± SD) | 68.0 ± 6.9 | 68.5 ± 8.3 | 0.58 |
| White race | 86.4% | 82.1% | 0.30 |
| Hispanic ethnicity | 3.3% | 2.1% | 0.75 |
| Female gender | 25.7% | 29.7% | 0.47 |
| Exposures, symptoms, and physiologic measures | |||
| Lives with a smoker | 13.6% | 17.2% | 0.37 |
| Current smoker | 33.2% | 24.8% | 0.10 |
| Pack-years tobacco cigarette smoking (mean ± SD) | 65.7 ± 39.2 | 57.7 ± 26.7 | 0.03 |
| Wheeze or whistling in chest | 55.1% | 51.7% | 0.52 |
| Nasal dryness or bloody nose or discharge ≥ 1x/mo | 40.7% | 43.5% | 0.66 |
| MMRC dyspnea score | |||
| 1 | 28.0% | 22.8% | 0.37 |
| 2 | 30.4% | 32.4% | |
| 3 | 34.6% | 40.7% | |
| 4 | 7.0% | 4.1% | |
| Body mass index (kg/m2; mean ± SD) | 29.9 ± 6.8 | 27.2 ± 5.7 | <0.0001 |
| Hemoglobin (g/dL; mean ± SD) | 14.6 ± 1.5 | 14.4 ± 1.4 | 0.12 |
| 6-minute walk distance (ft; mean ± SD) | 1035 ± 319 | 1100 ± 307 | 0.06 |
| Post BD FEV1 (L; mean ± SD) | 1.38 ± 0.47 | 1.22 ± 0.51 | 0.002 |
| Post BD FEV1 percent predicted (%; mean ± SD) | 48 ± 15 | 45 ± 18 | 0.08 |
| Post BD FEV1/FVC (mean ± SD) | 0.48 ± 0.13 | 0.44 ± 0.13 | 0.003 |
| Healthcare utilization and comorbidities | |||
| Pulmonary rehabilitation ever | 21.5% | 36.6% | 0.003 |
| Ever used home oxygen prior to entry | 29.4% | 30.3% | >0.99 |
| COPD exacerbation in 3 months prior to entry | 17.3% | 17.2% | 0.99 |
| Hospitalization in year prior to entry† | 23.2% | 20.8% | 0.69 |
| Coronary vascular disease | 38.3% | 24.8% | 0.009 |
| Diabetes | 23.8% | 13.8% | 0.02 |
| Osteoarthritis, sciatica, chronic back problem | 47.2% | 53.1% | 0.28 |
| Psychosocial measures | |||
| Ratings of Social Cognitive Theory constructs (scored 0–10) | |||
| Readiness to use oxygen (mean ± SD) | 7.6 ± 2.7 | 8.9 ± 1.9 | <0.0001 |
| Confidence in using oxygen (mean ± SD) | 8.4 ± 2.1 | 8.8 ± 1.6 | 0.02 |
| Importance of using oxygen (mean ± SD) | 7.8 ± 2.5 | 8.3 ± 2.3 | 0.05 |
| SGRQ total score (mean ± SD) | 49.7 ± 19.3 | 50.7 ± 16.9 | 0.60 |
| Epworth sleepiness score (mean ± SD) | 7.3 ± 4.0 | 6.3 ± 3.8 | 0.03 |
SD = standard deviation; MMRC = modified Medical Research Council; FEV1 = forced expiratory volume in 1 second; FVC = forced vital capacity; COPD = chronic obstructive pulmonary disease; SGRQ = St. George’s Respiratory Questionnaire.
*
Fisher’s exact test, chi-square test, or t-test for difference between groups.
†
Status re: hospitalization in year prior to entry was missing for 24 continuous patients and 1 intermittent patient; collection of this data item began after protocol revisions instituted in September 2009