Small airways dysfunction is associated with increased exacerbations in patients with asthma

There is a poor understanding of why some patients with asthma experience recurrent exacerbations despite high levels of treatment. We compared measurements of peripheral ventilation heterogeneity and respiratory system mechanics in participants with asthma who were differentiated according to exacerbation history, to ascertain whether peripheral airway dysfunction was related to exacerbations. Three asthmatic groups: stable (no exacerbations for > 12 mo, n = 18), exacerbation-prone (>= 1 exacerbation requiring systemic corticosteroids within the last 12 mo, but stable for >= 1-mo, n = 9), and treated-exacerbation (exacerbation requiring systemic corticosteroids within the last 1 mo, n = 12) were studied. All participants were current nonsmokers with < 10 pack yr smoking history. Spirometry, static lung volumes, ventilation heterogeneity from multibreath nitrogen washout (MBNW), and respiratory system mechanics from oscillometry were measured. The exacerbation-prone group compared with the stable group had slightly worse spirometry [forced expired volume in 1 s or FEV1 z-score -3.58(1.13) vs. -2.32(1.06), P = 0.03]; however, acinar ventilation heterogeneity [S-acin z -score 7.43(8.59) vs. 3.63(3.88), P = 0.006] and respiratory system reactance [X-rs cmH(2)OmiddotsmiddotL(-1) -2.74(3.82) vs. -1.32(1.94), P = 0.01] were much worse in this group. The treated-exacerbation group had worse spirometry but similar small airway function, compared with the stable group. Patients with asthma who exacerbate have worse small airway function as evidenced by increases in Sacin measured by MBNW and delta X-rs from oscillometry, both markers of small airway dysfunction, compared with those that do not. NEW & NOTEWORTHY This study assessed the relationship between peripheral airway function, measured by multiple breath nitrogen washout and oscillometry impedance, and exacerbation history We found that those with a history of exacerbation in the last year had worse peripheral airway function, whereas those recently treated for an asthma exacerbation had peripheral airway function that was comparable to the stable group. These findings implicate active peripheral airway dysfunction in the pathophysiology of an asthma exacerbation.

Automated summary

This study found that asthmatic patients with a history of exacerbations in the last year had worse peripheral airway function, while those recently treated for an asthma exacerbation had comparable peripheral airway function to the stable group. These findings suggest that active peripheral airway dysfunction may play a role in the pathophysiology of asthma exacerbations.