[Assessment of intrapulmonary ventilation disorders in children with bronchial asthma using the nitrogen elimination technique].

Stratification of functional abnormalities evaluated by whole-body plethysmography in asthmatic children can be characterized into three functional groups: pulmonary hyperinflation (H: TGV > mean + 2SD), bronchial obstruction (O: Raw > mean + 2SD) and a mixed type, group M, including both abnormalities. The multibreath nitrogen washout (MBNW) offers the possibility to measure FRC and calculate the amount of trapped gases (TG = TGV-FRCMBNW). Furthermore ventilation inequalities can be estimated by mathematical analysis of the washout curve from which indexes such as the lung clearance index (LCI), the mean dilution number (MDN) and the moment ratio (m2:m0 = M-ratio) can be obtained. In 69 asthmatic children (age 5-17 y; 38 boys, 31 girls) body plethysmography and MBNW were performed in the symptom free interval. The questions were, at what extend TG are present within the different functional groups, and which parameters best describe ventilation inequalities. The group attribution was H: 23, M: 16, O: 30. The highest amount of TG was found in H (36.4 +/- 22.2% TGV), then in M (26.6 +/- 23.1% TGV) and in O (19.4 +/- 16.0% TGV). In 33/50 cases presenting with normal TGV, TG mainly was at cost of a low FRC (13 in H, 8 im M, 12 in O). In 19 cases FRC was higher than TGV (3 in H, 1 in M 15 in O). TG was closely related with LCI, MDN and M-ratio. Most pronounced ventilation inequalities were found in group M showing a correlation only with FRC, but not with TGV.(ABSTRACT TRUNCATED AT 250 WORDS)