Highlights box:
What is already known about this topic? Inversion of the
reactance curve was anecdotally reported in cystic fibrosis (a disease
characterized by small-airway dysfunction [SAD] and inhomogeneity
ventilation). We speculate that this also can occur in asthma.
What does this article add to our knowledge? We describe, for
first time, that 65.5% of persistent asthmatic children have inversion
of the reactance curve and X5 approx. correction. The presence of X5
approx. decreases with age and correlates more closely than X5 with
other IOS parameters for the evaluation of SAD.
How does this study impact current management guidelines?Inversion of the reactance curve and X5 approx. could be more useful
parameters in the IOS to adjust the asthma treatment (especially the
ultrafine inhaled corticosteroids).Abstract:
Background: Small airway dysfunction in asthma can be measured
by impulse oscillometry (IOS), where sometimes the reactance can exhibit
an inversion of the curve, and its correction can determine a new value
for X5: approximate X5 (X5 approx.). Our hypothesis is that X5 approx.
exhibits a closer association with parameters of airway dysfunction in
the IOS than X5. Methods : We analyzed 403 children (3-17 years
old) who performed IOS (Sentry Suit, Vyntus®) and
spirometry, recording R5, AX, X5, X5approx., Fres, D5-20 and
FEF25-75. Groups X5 and X5 approx. were compared with
respect to the percentage of abnormal IOS parameters, their averages,
FEF25-75, and their correlation with each IOS parameter.
Also, we explored the correlation
between X5 and X5 approx. with each IOS parameter. Results: We
found a significant decreasing prevalence of X5 approx. with age (84.6%
in preschoolers, 67.2% in schoolchildren, and 36.5% in adolescents, p
for trend <0.001). The preschoolers and schoolchildren with X5
approx. exhibited significant (p<0.05) alterations in many
other IOS parameters (e.g. R5, Fes, AX, and D5-20) compared with those
with X5. Adolescents exhibited a significant (p<0.01)
alteration only for D5-20. The means of R5, AX, and D5-20 were
significantly (p<0.01) higher in children with X5 approx. than
with X5. Finally, in the all the age categories, compared with X5, X5
approx. correlated better with other IOS parameters and
FEF25-75. Conclusion : The presence of X5
approx. decreases with age and correlates more closely than X5 with
other IOS parameters for the evaluation of small airway dysfunction.
Word count: 250