 Descriptive statistical analysis methods will be used. As all parameters will be normally distributes, means, standard deviations and corresponding 95 confidence intervals will be calculated with the StatsDirect software version 2.7.7, Altrincham, Cheshire, UK. For PD15-FEV1, PD20-FEV1, RDR, and FeNO the base 10 antilog will be calculated as previously suggested. 