2.2 MBW measurements
N2-MBW tests were performed using the Exhalyzer D device and Spiroware analysis software (v3.2.1, Eco Medics AG, Duernten, Switzerland) with weight-adjusted dead spaces and settings according to current consensus guidelines 13,14. Testing was performed with patients sitting upright and breathing through a mouthpiece. Quality control was performed according to current guidelines and tests with at least two acceptable MBW trials were included in our analysis 14-16.