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Update in paediatric lung disease
P89 Ventilation heterogeneity is a feature of children with severe asthma and normal spirometry
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  1. A Nuttall1,
  2. C Beardsmore2,
  3. E Gaillard3
  1. 1Department of Infection, Immunity and Inflammation, College of Medicine, Biological Sciences and Psychology, University of Leicester, Leicester, UK
  2. 2Department of Infection, Immunity and Inflammation, College of Medicine, Biological Sciences and Psychology, Leicester Institute for Lung Health, NIHR Leicester Respiratory Biomedical Research Unit, University of Leicester, Leicester, UK
  3. 3Department of Infection, Immunity and Inflammation, College of Medicine, Biological Sciences and Psychology, Leicester Institute for Lung Health, NIHR Leicester Respiratory Biomedical Research Unit, University of Leicester and University Hospitals of Leicester NHS Trust, Leicester, UK

Abstract

Introduction Ventilation heterogeneity (VH) is a feature of a subgroup of adults with asthma (Verbanck et al. AJRCCM 1999; 159.5:1545–1550), however less is known regarding VH in childhood asthma. Previous data indicates VH is raised in asthmatic children compared with controls, and may be particularly high in those with severe or poorly controlled asthma. This may be important as many children report poor symptom control, despite normal spirometry.

Objectives We aimed to study the relationship between ventilation heterogeneity, disease severity, and symptom control in children with asthma.

Methods Stable asthmatic children were recruited from the Difficult Asthma Clinic, with controls recruited from diabetes clinic patients and their siblings. Asthma severity was classified in accordance with GINA guidelines (Step 1–3=Mild Moderate, Step 4–5=Severe). Asthmatics completed C-ACT/ACT to assess symptom control (score ≤19 = uncontrolled). All children performed Spirometry. Ventilation heterogeneity was assessed using Multiple-Breath Nitrogen Washout (MBNW) (Exhalyzer-D, Ecomedics). MBNW was performed in triplicate, with Lung Clearance Index (LCI) and indices of ventilatory heterogeneity in conductive and acinar airways (Scond and Sacin, respectively) calculated.

Results 35 participants aged 7–16 completed testing (7 controls, 7 mild-moderate asthma, 21 severe asthma). Results for MBNW displayed in Table 1. All MBNW parameters were normal in control subjects. Only the severe asthmatics had MBNW Results significantly higher than controls (LCI p= 0.006 , Scond p= 0.021 , Sacin p= 0.040 ). LCI was raised in 1/7 mild-moderate and 13/21 severe asthmatics. Scond was raised in 2/7 mild-moderate and 11/21 severe asthmatics. Sacin was raised in 1/7 mild-moderate and 4/21 severe asthmatics. 18/28 asthmatics had uncontrolled symptoms as assessed by the C-ACT/ACT. Of these, 14 had abnormal LCI but only 4 had abnormal FEV1. 8/28 asthmatics had raised LCI despite normal FEV1.

View this table:
Abstract P89 Table 1

MBNW results, displayed as median (range). Comparisons made using mann-whitney test, *p<0.05=significant

Conclusions LCI, a measure of ventilation heterogeneity, is raised in a high proportion of children with severe asthma. Most children with raised LCI had normal spirometry. This suggests that LCI is more sensitive to detect lung function deficits in asthma compared to spirometry. LCI also correlates well with symptom control. MBNW and LCI may be useful in the monitoring of children with severe asthma.

https://doi.org/10.1136/thoraxjnl-2017-210983.231

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