TABLE 1

Changes and discordances during methacholine challenge between interrupter resistance (R_int) and transcutaneous partial pressure of oxygen (P_tcO₂)

	Responsive children	Nonresponsive children
Subjects n	20	7
Changes in P_tcO₂ %	−25.4±4.8	−13.4±8.4
Changes R_{int_insp} %	+49.1±29.6	+13.2±11.4
Change R_{int_exp} %	+34.3±27.9	+8.8±17.4
Discordance between R_{int_insp} and P_tcO₂ n (%, 95% CI)	11 (55, 34–74)	0 (0, 0–35)
R_int increase <35% at PD₂₀P_tcO₂ n	6
R_int increase ≥35% before PD₂₀P_tcO₂ n	5
Discordance between PD₃₅R_{int_insp}+S_{pO_2,3%} and P_tcO₂ n	6	0
Discordance between R_{int_exp} and P_tcO₂ n (%, 95% CI)	16 (80, 58–92)	3 (42, 16–75)
R_int increase <35% at PD₂₀P_tcO₂ n	10	0
R_int increase ≥35% before PD₂₀P_tcO₂ n	6	3
Discordance between PD₃₅R_{int_exp}+ S_{pO_2,3%} and P_tcO₂ n	9	3

Data are presented as mean±sd percentage of post-diluent values unless otherwise stated. Changes are at the provocative dose of methacholine causing a 20% decrease in P_tcO₂ (PD₂₀P_tcO₂) in responsive children and at the last dose of methacholine in nonresponsive children. Discordances between R_int and P_tcO₂ changes were assessed at every steps of the test. R_int changes are more or less than 35% increase from the post-diluent value (PD₃₅R_int). R_{int_insp}: inspiratory interrupter resistance; R_{int_exp}: expiratory interrupter resistance; PD₃₅R_{int_insp}: provocative dose of methacholine causing a 35% decrease in R_{int_insp}; S_{pO_2,3%}: at least 3% decrease in transcutaneous saturation of oxygen from the post-diluent value; PD₃₅R_{int_exp}: provocative dose of methacholine causing a 35% decrease in R_{int_exp}.