Change in Inhaler Use, Lung Function, and Oxygenation in Association with Symptoms in COPD

Despite clinical guidelines for chronic obstructive pulmonary disease (COPD) patients to self-treat worsening respiratory symptoms with supplemental inhaler/nebulizer use, few studies have investigated if symptom changes are associated with differences in oxygenation, lung function, or self-treatment. A total of 26 former smokers (mean age 72.7 ±7.5 years; 57.7% female) with COPD (≥ Global Initiative for Chronic Obstructive Lung Disease Stage 2) were followed for up to 4 months, during which they recorded daily oxygenation, lung function, and inhaler/nebulizer use. Differences in these health measures were assessed in association with self-reported worsening symptoms and COPD exacerbations, as defined by validated questionnaire. We collected 2451 observations with spirometry and questionnaire data and identified 253 symptom days (10.3%) and 47 (1.92%) exacerbation days. In linear mixed effects models adjusted for age, sex, race, height, weight, and season, each respiratory symptom reported worse than baseline was associated with a 0.19 percentage point (95% CI -0.31 to -0.07) lower daily oxygen saturation (p=0.002). On major symptom days (defined as worse-than-baseline dyspnea, sputum purulence or sputum amount), oxygen saturation was 0.56 percentage points lower (95% CI -0.89 to -0.23, p=0.001) than days without increased major symptoms. We found no association of symptom days or exacerbations with forced expiratory volume in 1 second. There were 8 reports of increased inhaler/nebulizer use from baseline on symptom days (1.5% of 253). In this moderate-to-severe COPD population, worsening respiratory symptoms were common and associated with lower oxygenation. However, participants did not self-treat symptoms with increased inhaler/nebulizer use, which may suggest poor perceived clinical benefit from short-acting bronchodilators and a potential target for patient education.