Figure 2. Ivacaftor acutely reduces sweat Cl^– concentration and increases forced expiratory volume in 1 second.

(A) Sweat Cl^– concentration, (B) forced expiratory volume in 1 second (FEV₁%), and (C) airway surface liquid (ASL) pH on day 0 and 2 days after beginning ivacaftor. Each pair of data points and connecting lines indicate a different person. n= 22 for sweat [Cl^–] and FEV₁%; n= 21 for ASL pH (1 person declined ASL pH measurements). Bars and whiskers indicate mean ± SD. We did not detect an effect of sex or genotype on the results. *P < 0.001 by Wilcoxon matched-pairs signed-rank test.