Search

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 [Sacin z-score 7.43(8.59) vs. 3.63(3.88), P = 0.006] and respiratory system reactance [Xrs cmH2O⋅s⋅L-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 ΔXrs 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. [ABSTRACT FROM AUTHOR]

Background The association between grass pollen exposure and lung function changes and airway inflammation is limited. We investigated these associations in a community-based sample, and whether any such associations were modified by current asthma, current hay fever, pollen sensitization and age. Methods Cross-sectional analyses of data from the Melbourne Atopy Cohort Study (MACS) participants (n = 936). Lung function was assessed using spirometry. Airway inflammation was assessed by fractional exhaled nitric oxide (FeNO), and exhaled breath condensate pH and nitrogen oxides (NOx). Daily pollen counts were collected using a volumetric spore trap. The associations were examined by linear regression. Results Higher ambient levels of grass pollen 2 days before (lag 2) were associated with lower mid-forced expiratory flow (FEF25-75%) and FEV1/FVC ratio (Coef. [95% CI] = -119 [-226, -11] mL/s and -1.0 [-3.0, -0.03] %, respectively) and also 3 days before (lag 3). Increased levels of grass pollen a day before (lag 1) was associated with increased FeNO (4.35 [-0.1, 8.7] ppb) and also at lag 2. Adverse associations between pollen and multiple outcomes were greater in adults with current asthma, hay fever and pollen sensitization. Conclusions Grass pollen exposure was associated with eosinophilic airway inflammation 1-2 days after exposure and airway obstruction 2-3 days after exposure. Key messages There is a more delayed effect on lung function compared to airway inflammation. Adults with current asthma, hay fever and grass pollen sensitisation are especially vulnerable. [ABSTRACT FROM AUTHOR]