- Severity of Disease: A pre and post-albuterol/salbutamol Forced Expiratory Volume in One Second /Forced Vital Capacity (FEV1/FVC) ratio of <0.70 and post-albuterol/salbutamol FEV1 of <=70% of predicted normal values at Visit 1 (Screening) calculated using reference values provided by Quanjer.