Background It is unknown if small airways dysfunction persists in asthmatics receiving standard community treatment. Impulse oscillometry (IOS) is a sensitive measure of small airways function. We wished to assess the degree of small airways dysfunction in a cross-section of community-managed asthmatics.
Methods We analysed primary care referral data from persistent asthmatics (n=378) receiving standard community therapy, screened using spirometry and IOS. We compared patients by British Thoracic Society asthma treatment step (2–4).
Results Step 2 were not different from step 3 patients receiving long-acting beta-agonist (LABA). Step 4 patients differed from step 2 by: higher inhaled corticosteroid (ICS) dose (p<0.0001); lower forced expiratory volume in 1s (FEV1%, p=0.02) and forced mid-expiratory flow (FEF25–75%, p=0.001); higher frequency of resonance (Fres, p=0.02) and peripheral airway resistance (R5-R20, p=0.006); while for steps 3 vs. 4, there were differences in Fres (p<0.05) and R5-R20 (p=0.006). There were high proportions of abnormality for R5-R20 (>0.03kPa/L/s) at steps 2, 3 & 4 respectively: 64.6%, 63.5% and 69.9%. Step 2 patients receiving extra-fine particle ICS demonstrated lower total airway resistance at 5Hz (R5) versus patients receiving standard ICS (124.1% vs. 138.3%, p<0.05), with no difference in FEV1 (Table 1). At step 4, R5 remained elevated at 141.3% despite concomitant LABA, with only 2.4% using extra-fine ICS.
Conclusion There is persistent small airways dysfunction despite treatment at steps 2–4 of current asthma guidelines. Extra-fine ICS may reduce airway resistance at step 2. Prospective studies with extra-fine ICS±LABA at steps 2–4 are required to discern whether improving small airways function might result in long-term improved control.
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