“…Patients were constantly asked to complete 3 minutes for each stage and once the peak volitional effort was achieved the test was terminated [15,17]. During GXT, the patient breathed through a face mask (Hans Rudolph Inc, Kansas City, MO, USA) that connected to a calibrated expired gas analysis system (Zan-680 Ergospiro Ergospirometry System, manufactured by ZAN Me Bgerate GmbH, Germany).…”