Introduction: Xe-MRI directly images the distribution of ventilation in the lung making it ideal for assessing bronchodilator response (BDR). Here we compared BDR using Xe-MRI, spirometry and airwave oscillometry (AOS) to determine if the magnitude of BDR is related to diagnosis or disease severity.

Methods: 136 patients from primary care with asthma and/or COPD taking part in the NOVELTY study [NCT02760329] were assessed pre and post-BD with Xe ventilation MRI, spirometry and AOS. From Xe-MRI, the ventilation defect percent (VDP) assesses the proportion of non-ventilated lung and the treatment response map (TRM) quantifies voxel by voxel changes in ventilation. The magnitude of change (?) post-BD was compared by diagnosis and by FEV1 %predicted severity (mild >80%, moderate 50-80%, severe <50%).

Results: Patients were aged 29-83years (53% female). 72 patients had a diagnosis of asthma, 41 had asthma+COPD and 23 had COPD. All PFT and Xe-MRI metrics had a statistically significant change post-BD for all patients and within diagnosis group (p<0.001). There were no significant differences between diagnosis groups for ?PFT or ?Xe-MRI metrics post-BD. 93 patients had mild FEV1 severity, 34 moderate and 9 were severe. ?FEV1 and ?AOS were not different between severity groups, however there was an increase in ?VDP (p=0.02), TRM (p<0.001) and ?FVC (p=0.001) with increasing severity.

Conclusions: There was no difference in the magnitude of ?PFT and ?Xe-MRI metrics post-BD between asthma and/or COPD. The ?FEV1 was also un-related to disease severity, however the magnitude of Xe-MRI BDR is effective at distinguishing disease severity and therefore especially useful in assessing more severe disease.