Abstract
Introduction: There have been no studies investigating the relationship between small airway dysfunction and long-term asthma control in adults.
Aim: We evaluated whether small airways dysfunction was associated with worse control in asthmatics with a preserved FEV1(FEV1>80%).
Methods: Spirometry and impulse oscillometry measurements were linked to a health informatics database for oral corticosteroid and short-acting beta-agonist (SABA) use. We evaluated if small airways dysfunction, defined by a FEF25-75<70% or FEV1/FVC<0.80 or peripheral airway resistance as R5-R20>0.07 kPa·L-1·s was associated with increased oral corticosteroid and SABA use.
Results: 302 out of 442 (68%) asthmatics had a preserved FEV1>80%, mean age:40 years, FEV1:97%, median ICS dose:800µg, 42% taking LABA. Comparing FEF25-75<70% vs >70% the odds ratio OR(95% CI) for oral corticosteroid and SABA use were 1.67(1.04 -2.68)and 2.00(1.27-3.16) respectively. Comparing R5-R20>0.07 kPa·L-1·s vs <0.07 kPa·L-1·s; OR were 1.99(1.23-3.19) and 1.83(1.16-2.89) and for FEV1/FVC<0.80 vs >0.80; OR were 2.06(1.27-3.35) and 1.61(1.02-2.54). The OR increased when patients had more than one abnormal small airway parameter.
Conclusions: In adult asthmatics with preserved FEV1, small airways dysfunction determined by FEF25-75, FEV1/FVC and R5-R20 was associated with poorer control, suggesting the presence of a defined small airway asthma phenotype.
- © 2014 ERS