Spirometry and multiple breath nitrogen washout (MBNW) before and after cold dry air challenge (CACh) in children and adolescents with asthma

Abstract

Background and Aim: Airway hyperresponsiveness (AHR) is a common feature of asthma, and is associated with airway inflammation and ventilation heterogeneity. We wanted to compare cold dry air challenge induced changes as assessed by spirometry and MBNW. Methods: Subjects with clinically stable asthma were studied by measurement of exhaled nitric oxide (FENO), followed by spirometry and MBNW before and after eucapnic CACh (4 min hyperventilation of -10° dry air at FEV1 x 22.5). Results: 39 (19 f) subjects with a mean age of 13.6 yrs (range 6.5-18.6), a mean FEV1 of 98% pred. (SD 11.6), a mean LCI of 6.55 (SD 0.4), and a mean FENO of 38 ppb (range 0.4-168) were studied. Mean fall in FEV1 % pred. after CACh was -5.65 (range 3.2 to -65), and mean change in LCI was 0.33 (range -0.8 to 3.68). 10/39 subjects were hyperresponsive as defined by ≥9% fall in FEV1. The fall in FEV1 correlated to the increase in LCI (r = -0.72, p<0.01). The 10 subjects with AHR showed a higher mean Scond (ventilation heterogeneity in conducting airways) before CACh than the 29 normoreactive patients: 0.027 (SD 0.02) vs. 0.019 (SD 0.01). In the group with AHR a correlation between fall in FEV1 and changes in Sacin (ventilation heterogeneity in the acinar lung zone) after CACh was observed (r = -0.75, p<0.01). Mean FENO was higher in subjects with AHR: 75 (SD 70) vs. 26 (SD 27) ppb. Conclusions: In children and adolescents with AHR an LCI-increase corresponded well to FEV1-decline after CACh. Baseline ventilation heterogeneity as assessed by Scond could be a predictor of AHR; further measurements are warranted to confirm these preliminary data.