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May 2, 2022 / in Scientific Article

Abstract

Background

Airflow obstruction in asthma is associated with increased risk of morbidity and exacerbations. A number of reports have identified that small airways obstruction (SAO) may be present in asthma in the presence or absence of fixed airflow obstruction (FAO). We sought to evaluate the prevalence of SAO and its clinical expression in the presence or absence of FAO.

Methods

132 adult asthmatics (GINA 1(11), GINA 2-3 (30) GINA 4-5 (89)) were recruited from Glenfield Hospital. All patients underwent impulse oscillometry and spirometry with reversibility. Two markers of SAO were evaluated (R5-R20 and AX). Due to the lack of robust reference equations for predicted impulse oscillometric parameters of SAO, we defined 'abnormal' as a value above the asthmatic mean.

Results

We identified that 23.5 % and 15.2% of patients with asthma had SAO in the presence of a normal post bronchodilator FEV1/FVC >70% - when evaluating the markers AX and R5-R20 respectively. A similar percentage had SAO and FAO for both markers (24.2% for AX and 19.7% for R5-R20). The frequency of asthma exacerbations in the previous year was significantly elevated (3.13/yr (AX), 3.53/yr (R5-R20)) in patients with isolated SAO compared to patients without SAO and spirometric airflow obstruction (1.29/yr (AX), 1.64/yr (R5-R20)) [p=0.0014 ANOVA, p>0.05 intergroup comparison]. There were no differences in eosinophilic airway inflammation between the groups.

Conclusion

We have identified that isolated small airways obstruction is associated with asthma exacerbations independently of eosinophilic airway inflammation. Further studies are required to evaluate whether treating isolated SAO may reduce the frequency of asthma exacerbations.


The articles include uses of tremoflo products or describes research devices that may not have been cleared by FDA
Source

Soares M, Gonem S, Singapuri A, Hargadon B, Brightling C, Siddiqui S. Small airways obstruction and asthma exacerbations. Eur Respir J [Internet]. 2014 Sep 1 [cited 2019 Jun 14];44(Suppl 58):P3004

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Longitudinal monitoring of asthma in the clinic using respiratory oscillometry
Asthma guidelines emphasize the importance of assessing lung function and symptoms. The forced oscillation technique (FOT) and its longitudinal relationship with spirometry and symptoms are unresolved. We examined concordance between longitudinal spirometry, FOT and symptom control, and determined FOT limits of agreement in stable asthma.
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We read with interest the article in the June 2020 issue of CHEST from Cottee et al,1 examining 52 patients with asthma, which concluded that bronchodilator response to albuterol 400 mg using forced oscillation technique (airway oscillometry [AO]) with Thorasys Tremoflo was more sensitive than spirometry at identifying poor disease control with the asthma control test.1 This pattern was observed for reactance area (AX) and reactance at 5Hz but not for resistance at 5Hz (R5).
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In an issue of CHEST (September 2020), Karakioulaki et al1 reinforced mounting evidence for the presence of regionally heterogeneous airway abnormalities in patients with asthma by showing histopathologic airway differences across lung lobes on endobronchial biopsy. At the lobar level, airway smooth muscle cell mass and the distance between the basement membrane and airway smooth muscle were significantly different across lobes. Airway smooth muscle cell mass was greater in lower lobes compared with upper lobes, and, although specific interlobar differences were not measured, the right upper lobe notably exhibited the least amount of airway smooth muscle mass.
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