Abstract
BACKGROUND: Chronic hypoxemia in patients with COPD is associated with increased morbidity and mortality. Although arterial partial pressure of oxygen (PaO(2)) is widely used, it does not adequately reflect systemic oxygen transport. Arterial oxygen content (CaO(2)) may provide a more comprehensive assessment. OBJECTIVE: This study aimed to evaluate whether or not CaO(2) is a better predictor of mortality than PaO(2) in patients with COPD. METHODS: This retrospective observational cohort study included 147 COPD patients aged ≥45 years. Patients were categorized according to CaO(2) levels (low, normal, high). Mortality at 1, 3, and 5 years was analyzed. Statistical methods included ROC curves, Kaplan-Meier survival analysis, and Cox regression models. RESULTS: A total of 66 deaths (45.2%) occurred in the study cohort. Mortality was highest in the low CaO(2) group. The CaO(2) demonstrated better predictive performance than PaO(2) (AUC 0.73 versus 0.53, respectively). Low CaO(2) was associated with a 2.5-fold increased risk of mortality. Despite improvements in PaO(2) after long-term oxygen therapy, CaO(2) did not significantly change. CONCLUSIONS: The CaO(2) is a more informative marker of oxygen transport and mortality risk than PaO(2) in COPD patients. It should be considered a complementary parameter in clinical assessment.