Variation in respiratory mechanic among cftr genotypes. Values for Raw(A), G(B), H(C), and η(D) were determined by fitting the constant-phase model to measurements of Zrs from cftr+/+ (Black), cftr+/- (Green) and cftr-/- (red) genotypes. All measures were normalized by multiplication by lung weight. Error bars are +/- standard deviation. *p < 0.05 when compared to cftr+/+ and **p < 0.05 when compared to cftr+/-.