Bronchodilator responsiveness over time in SPIROMICS: Clinical characteristics

Abstract

Background: Bronchodilator responsiveness (BDR) is seen in COPD and asthma.

Aims: We identified COPD patients from the SPIROMICS cohort with BDR on multiple test visits and compared their clinical characteristics with patients who never showed BDR.

Methods: BDR was defined by the ATS/ERS criteria of an increase in either FVC and/or FEV₁ of ≥12% and ≥200 ml after inhaled albuterol and ipratropium. Of 2,275 subjects with two or more SPIROMICS visits, 350 (15%) were classified as always showing BDR (ABDR) and 895 (39%) never showed BDR (NBDR). Others showed variable responses.

Results: More ABDR subjects had a self-reported history of asthma (29% v 15%) and more reported exacerbations in the year prior to enrolment (31% v 18%). ABDR had greater smoking history (52 v 46 pack-years*) but there was a similar proportion of current smokers in each group (42 v 38% respectively). Of the NBDR group, 73.8% were GOLD stages 0 or 1 whereas of the ABDR group, 83.7% were GOLD stages 2, 3 or 4. The ABDR group had worse baseline pre- and post-bronchodilator (BD) FEV1 and FVC compared with the NBDR group: pre-BD FEV1 1.37 v 2.40 L; pre-BD FVC 2.91 v 3.54 L. ABDR had thicker airway walls (Pi10 3.72 v 3.70 mm), more air trapping (PRM fSAD 29% v 14%) and more emphysema by HRCT (<-950 HU 10% v 5%). Subjects with BDR versus those without BDR at baseline had faster decline of FEV₁ when followed up to 8 years (51 v 35 ml/year). P<0.001 for all comparisons.

Conclusions: Bronchodilator responsiveness in SPIROMICS was more likely in moderate-to-severe COPD, associated with a self-reported asthma history, more air trapping, more emphysema and faster decline of FEV₁. These findings highlight pathophysiological similarities between COPD and asthma.