Background and objective: It is known that biomarkers of systemic inflammation are raised in COPD caused by tobacco (T-COPD) compared with healthy controls, but there is less information on the inflammatory status of subjects with COPD caused by biomass smoke (B-COPD). In addition, the possible (if any) differences in inflammation between both types of the disease are still not well known. The aim of this study was to assess the inflammatory profile in B-COPD and T-COPD. Methods: A total of 20 subjects (15 men and five women) with T-COPD were matched one to one for sex, age and forced expiratory volume in 1 s (FEV₁) to 20 B-COPD patients. In all, 20 sex-matched healthy subjects with normal lung function without smoking history or biomass exposure were included as controls. The following biomarkers were measured: exhaled nitric oxide, serum IL-6, IL-8, IL-5, IL-13, periostin, surfactant protein-P, TNF-α, IgE, erythrocyte sedimentation rate, C-reactive protein and fibrinogen. Complete blood count was also obtained. Results: The age of the subjects was 70.2±7.9 years and FEV₁% was 56.2%±14.6%. Most inflammatory biomarkers were higher in both types of COPD than in healthy controls. IL-6, IL-8 and IL-5 were significantly higher in T-COPD than in B-COPD, without other significant differences. Conclusion: Both types of COPD are associated with high levels of systemic inflammation biomarkers. T-COPD patients have a higher systemic inflammatory status than the patients with B-COPD.

BACKGROUND: Distance walked during the 6-min walk test (6MWT) predicts mortality in COPD. The body weight of the patient affects the work required to walk. Calculated work during the 6MWT (6MWT work) may account for differences in walk distance resulting from change in body weight. Thus, 6MWT work might be a better predictor of mortality than distance walked. This study was designed to test this hypothesis and to assess if other variables measured during the 6MWT, like continuous oximetry recording, offered additional prognostic information. METHODS: This was a retrospective analysis of prospectively collected data; 104 COPD patients were studied. 6MWT was performed in all cases. 6MWT work was calculated as body weight (in kg) × distance walked (in m). Receiver operating characteristic curves were used to assess the value of variables to predict mortality. Additional analysis was performed using Kaplan-Meier survival plots and Cox proportional hazards regression models. RESULTS: Mean follow-up was 590 ± 472 d. Eleven subjects (10.6%) died. 6MWT work was not better than distance walked to predict mortality (area under the curve 0.77 for 6MWT work vs 0.80 for distance; difference 0.03, 95% CI −0.05 to 0.12, P = .45). Subjects who died had more dyspnea (measured using the Borg scale) after the 6MWT (8.5 vs 4.0, P < .001), lower baseline SpO₂ (85% vs 93%, P = .001), worse oxygen saturation during the 6MWT (mean SpO₂ while walking 74.0% vs 86.6%, P = .02) and walked less distance (255 m vs 480 m, P = .001). On multivariate analysis, only 6MWT distance and dyspnea after the test correlated independently with mortality (P = .005 for both variables). CONCLUSIONS: 6MWT work was not more useful than 6MWT distance to predict mortality. The study confirms that 6MWT distance and dyspnea on exertion are key elements in prognostic evaluation in COPD, while the value of exercise oxygen desaturation is less clear.