Spirometry measurements
Spirometry measurements were conducted using a Vyntus® APS/IOS (Vyaire GmbH, Höchberg, Germany), calibrated daily with a 3 L syringe according to the manufacturer’s instructions, and analysed using the SentrySuite® software package (version 3.10). Spirometry was performed in accordance with ATS/ERS guidelines and after explanation and demonstration of the correct execution technique [57]. Among measurements fulfilling acceptability and usability criteria, three acceptable flow volume loops (FVL) were selected, with the second highest forced vital capacity (FVC) and forced expiratory volume in 1 second (FEV1) within 0.1 L or 10% of the highest value.