Kristian Brat,1 Marek Plutinsky,1 Karel Hejduk,2 Michal Svoboda,2 Patrice Popelkova,3 Jaromir Zatloukal,4 Eva Volakova,4 Miroslava Fecaninova,5 Lucie Heribanova,6 Vladimir Koblizek7 1Department of Respiratory Diseases, Faculty of Medicine, University Hospital Brno, Masaryk University, Brno, Czech Republic; 2Faculty of Medicine, Institute of Biostatistics and Analyses, Masaryk University, Brno, Czech Republic; 3Pulmonary Department, University Hospital, Ostrava, Czech Republic; 4Pulmonary Department, University Hospital, Olomouc, Czech Republic; 5Department of Pneumology, Bulovka Hospital, Prague, Czech Republic; 6Department of Respiratory Medicine, Thomayer Hospital, Prague, Czech Republic; 7Pulmonary Department, Faculty of Medicine in Hradec Kralove, University Hospital Hradec Kralove, Charles University, Hradec Kralove, Czech Republic Background: Respiratory parameters are important predictors of prognosis in the COPD population. Global Initiative for Obstructive Lung Disease (GOLD) 2017 Update resulted in a vertical shift of patients across COPD categories, with category B being the most populous and clinically heterogeneous. The aim of our study was to investigate whether respiratory parameters might be associated with increased all-cause mortality within GOLD category B patients. Methods: The data were extracted from the Czech Multicentre Research Database, a prospective, noninterventional multicenter study of COPD patients. Kaplan–Meier survival analyses were performed at different levels of respiratory parameters (partial pressure of oxygen in arterial blood [PaO2], partial pressure of arterial carbon dioxide [PaCO2] and greatest decrease of basal peripheral capillary oxygen saturation during 6-minute walking test [6-MWT]). Univariate analyses using the Cox proportional hazard model and multivariate analyses were used to identify risk factors for mortality in hypoxemic and hypercapnic individuals with COPD. Results: All-cause mortality in the cohort at 3 years of prospective follow-up reached 18.4%. Chronic hypoxemia (PaO2 <7.3 kPa), hypercapnia (PaCO2 >7.0 kPa) and oxygen desaturation during the 6-MWT were predictors of long-term mortality in COPD patients with forced expiratory volume in 1 second ≤60% for the overall cohort and for GOLD B category patients. Univariate analyses confirmed the association among decreased oxemia (<7.3 kPa), increased capnemia (>7.0 kPa), oxygen desaturation during 6-MWT and mortality in the studied groups of COPD subjects. Multivariate analysis identified PaO2 <7.3 kPa as a strong independent risk factor for mortality. Conclusion: Survival analyses showed significantly increased all-cause mortality in hypoxemic and hypercapnic GOLD B subjects. More important, PaO2 <7.3 kPa was the strongest risk factor, especially in category B patients. In contrast, the majority of the tested respiratory parameters did not show a difference in mortality in the GOLD category D cohort. Keywords: mortality, hypoxemia, hypercapnia, COPD, GOLD 2017 update