Combined effects of lung function, blood gases and kidney function on the exacerbation risk in stable COPD: results from the COSYCONET cohort - Trudzinski, Franziska; Kahnert, Kathrin; Vogelmeier, Claus F.; Kauczor, Hans-Ulrich; Gogol, Manfred; Herth, Felix; Katus, Hugo; Virchow, Johann Christian (Respiratory medicine, 2019)