Increased arterial carboxyhemoglobin concentrations in chronic obstructive pulmonary disease

Rationale: Exhaled carbon monoxide (CO) and arterial blood carboxyhemoglobin concentrations (Hb-CO) increase in inflammatory pulmonary diseases. Objectives: To study whether arterial Hb-CO is useful to monitor disease activity in patients with chronic obstructive pulmonary disease (COPD) who had stopped smoking. Methods: We measured arterial Hb-CO, arteriovenous Hb-CO differences, and FEV, in 58 patients with COPD and 61 ex-smoking control subjects. Results: Arterial Hb-CO concentrations in patients at stable conditions were higher than those in control subjects (p < 0.0001). Furthermore, the Hb-CO concentrations in patients at the exacerbations (p < 0.0001) were higher than those at the stable conditions. Arterial Hb-CO concentrations in patients at stage III were higher than those in patients at stage II, and the Hb-CO concentrations in patients at stage IV were higher than those in patients at stage III at the stable conditions and exacerbations. Arterial Hb-CO correlated with exhaled CO in patients with COPD at stage II and stage III at the exacerbations. Arterial Hb-CO, inversely correlated with the arterial blood partial oxygen pressure and FEV1. Arteriovenous Hb-CO differences in patients at the exacerbations did not differ from those in patients at stable conditions and from those in control subjects. Moreover, arterial Hb-CO correlated with serum C-reactive protein values and serum lipid peroxide concentrations. Conclusions: These findings suggest that increased arterial Hb-CO may relate to severity in patients with COPD because of lung and systemic inflammation and production of reactive oxygen species.