Role of Anemia in Home Oxygen Therapy in Chronic Obstructive Pulmonary Disease Patients

Abstract

Anemia is a known comorbidity found in chronic obstructive pulmonary disease (COPD) patients. Hypoxemia is common and basically due to ventilation/perfusion (V/Q) mismatch in COPD. Anemia, by decreasing arterial oxygen content, may be a contributing factor for decreased delivery of oxygen to tissues. The objective of this study is to determine if anemia is a factor in qualifying COPD patients for home oxygen therapy. The study was designed as a retrospective, cross-sectional, observational chart review. Patients who were referred for home oxygen therapy evaluation were selected from the computerized patient record system. Demographic data, oxygen saturation at rest and during exercise, pulmonary function test results, hemoglobin level, medications, reason for anemia, comorbid diseases, and smoking status were recorded. The χ tests, independent sample t tests, and logistic regression were used for statistical analysis. Only 356 of total 478 patient referrals had a diagnosis of COPD over a 2-year period. Although 39 of them were excluded, 317 patients were included in the study. The overall rate of anemia was 38% in all COPD patients. Anemia was found significantly more frequent in COPD patients on home oxygen therapy (46%) than those not on home oxygen therapy (18.5%) (P < 0.0001). Mean saturation of peripheral oxygen values were significantly lower in anemic COPD patients both at rest and during exercise (P < 0.0001). Also, in COPD patients, age, Global Initiative for Chronic Obstructive Lung Disease class, smoking status, hemoglobin level, hematocrit, percent of forced expiratory volume in first second, forced expiratory volume in first second/forced vital capacity, residual volume/total lung volume, percent of carbon monoxide diffusion capacity were significantly different between home oxygen therapy and those not on home oxygen therapy (P < 0.05). Multivariate logistic regression showed that anemia remained a strong predictor for long-term oxygen therapy use in COPD patients after adjusting for other significant parameters. Anemic COPD patients are more hypoxic especially during exercise than those who are not anemic. We conclude that anemia is a contributing factor in qualifying COPD patients for home oxygen therapy.