129Xe-MRI and lung function to phenotype ventilation heterogeneity in asthma and/or COPD

Abstract

Patients with asthma and/or COPD are characterised by airflow obstruction. Significant spirometric overlap exists and sensitive metrics of ventilation heterogeneity may better phenotype each condition. <b>Methods:</b> Patients from primary care with asthma (Group 1), asthma+COPD (G2) or COPD only (G3) were assessed (NOVELTY study NCT02760329) with ¹²⁹Xe ventilation MRI, spirometry, lung clearance index (LCI) and oscillometry (AOS) on the same day and post-bronchodilator. Ventilation defect percentage (VDP) and heterogeneity index (VHI) were calculated from ¹²⁹Xe-MRI. <b>Results:</b> 164 patients (median [IQR] age=60.4 years [49.6,70.9] 52% female) were assessed, including 82 in G1, 55 in G2 and 27 in G3. Significant (p&lt;0.001) correlations between both VDP and VHI existed respectively with LCI (r=0.58,r=0.62), R5 (r=0.33,r=0.3), R5-20 (r=0.42,r=0.41), AX ((area of reactance curve) r=0.51,r=0.49), FEV₁ (r=-0.58,r=-0.59) and FEV₁/FVC (r=-0.72,r=-0.71). There were no significant differences between G2 and G3. However, G1 had significantly better lung function and ¹²⁹Xe-MRI, compared to G2 and G3. 127 patients (78-G1, 37-G2 and 12-G3) had an FEV₁ &gt;-1.64 z-score. Between groups, FEV₁, FEV₁/FVC and AOS metrics were not significantly different, however LCI, VDP and VHI were significantly (p&lt;0.001)&nbsp;worse in G2 and G3 when compared to G1 (but not between G2 and G3). In G1, 25% had abnormal AX, LCI=41% and VDP=49%. In G2, 44% had abnormal AX, LCI=65% and VDP=84%. In G3, 36% had abnormal AX, LCI=100% and VDP=100%. <b>Conclusion:</b>¹²⁹Xe VDP, VHI and LCI were raised in COPD when compared to asthma, even when FEV₁ was normal. In patients with asthma+COPD, ¹²⁹Xe-MRI and LCI may better identify asthma-like or COPD-like phenotypes.