Total Lung Capacity (TLC) of the lungs can be determined using a pressure based method (i.e. by body plethysmography) or it can be determined using a dilution based method (i.e. by single breath dilution during a CO diffusing capacity test). The results of the two methods differ, especially in patients with higher grades of COPD. The study investigates an improved analysis for the determination of TLC using the dilution method; this method has been suggested in the new ATS/ERS DLCO (diffusion capacity of lung for carbon monoxide) standard published in 2017. This study is based on approx. 120 participants. So far, there has not been a study using commercially available equipment.

Spirometry, lung volume measurement by body plethysmography and DLCO measurements will be performed on reference device (Masterscreen Body/Diff, Vyaire, USA), Spirometry and DLCO will also be performed on the device under test (EasyOne Pro LAB, ndd Medizintechnik AG, Switzerland) in a crossover design. Both devices are CE marked and FDA approved. The tests performed on both devices are standardized tests performed routinely with patients.

Inclusion Criteria:

3 groups

• Healthy subjects, FEV1/FEV1(pred) > 80%
• COPD GOLD classification 1 or 2, FEV1/FEV1(pred) ≥ 50%
• COPD GOLD classification 3 or 4, FEV1/FEV1(pred) < 50%

Exclusion Criteria:

• Smoked during 2 hours prior to measurements

Additional exclusion criteria for healthy subjects:

• BMI > 30
• Any relevant concomitant diseases (investigators decision)
• Any relevant concomitant medication (investigators decision)
• FEV1/FEV1(pred) <= 80%