The Mobile COPD Status Test (mCST)

In total 130 COPD patients will be included prospectively in this multicenter trial during an inpatient pulmonary rehabilitation program at the Schoen Klinik Berchtesgadener Land, Schönau am Koenigssee, (Germany) or during a stay (inpatient or outpatient) at the Klinikum Nuremberg (Germany). In general, the study is divided into two parts - study part I, within the duration of the pulmonary rehabilitation program/ hospital stay and study part II, in the home environment (24 weeks). Study part I: Visit 1 (day 0, in the clinic) + Visit 2\* (day 14+/-5, in the clinic/outpatient) Each study participant is given a smartphone. Under the guidance of study personnel, data collection of the following parameters is carried out via KAIA mCST App): * four standardized questions regarding coughing frequency, expectoration, chest tightness and shortness of breath during exercise * Dyspnea at rest * Breath sounds via microphone * Inspiration/expiration length via microphone * Respiratory rate via smartphone measurements * Physical performance via the sit-to-stand test (1min) with counting the repetitions and checking the correct execution via smartphone camera * Gait analysis (2x 10 steps walking) via acceleration sensors of the smartphone or via motion tracking by camera during defined gait measurements. The mCST app takes about 15 minutes to complete. Additionally, clinical routine data will be collected: * medical history * body plethysmography \& blood gases * EKG * health related quality of life * dyspnea * 6-minute walk distance * 1-minute-sit to stand test Study part II: Visits 3 to 26 (week 3 to 26, in participants home environment) From study visit 3 on, participants are observed weekly in their home environment for a total of 24 weeks. No further clinic visits take place. Disease activity is measured weekly as patient reported outcomes using the mCST app (for details see description of visit 1/2, part 1). In addition to the weekly mCST app, patients are invited to fill out daily a symptom diary before going to bed. The symptom diary contains the EXACT questionnaire and an activity questionnaire. \*Visit 2 is optional