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[Assessment of intrapulmonary ventilation disorders in children with bronchial asthma using the nitrogen elimination
R Kraemer1, S Pacozzi, C Casaulta Aebischer
1Universitäts-Kinderklinik Bern, Schweiz.
Insights
Asthmatic children show trapped gases (TG) and ventilation inequalities, particularly in hyperinflation groups. Multibreath nitrogen washout (MBNW) effectively quantifies these lung function abnormalities.
Area of Science:
- Pulmonary physiology
- Pediatric respiratory medicine
Context:
- Asthma in children presents with diverse functional abnormalities.
- Whole-body plethysmography categorizes these into hyperinflation (H), obstruction (O), and mixed (M) groups.
- Multibreath nitrogen washout (MBNW) provides advanced lung function metrics.
Purpose:
- To investigate the extent of trapped gases (TG) in different functional asthma groups.
- To determine which parameters best characterize ventilation inequalities using MBNW.
- To correlate TG and ventilation parameters with functional groups.
Summary:
- 69 asthmatic children underwent plethysmography and MBNW.
- Trapped gases were most prevalent in the hyperinflation group (H).
- Ventilation inequalities, assessed by LCI, MDN, and M-ratio, correlated with TG and were most pronounced in the mixed group (M), linked to FRC.
Impact:
- This study clarifies the role of trapped gases and ventilation heterogeneity in pediatric asthma.
- MBNW parameters are valuable for assessing functional deficits in asthmatic children.
- Findings aid in stratifying asthma severity and understanding pathophysiology.
Abstract:
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)