This Is What COVID-19 Survival Looks Like: 129Xe MRI, Oscillometry and Pulmonary Function Measurements

PURPOSE: COVID-19 lung infection has severe consequences that may persist following recovery including impaired oxygen transfer and local and systemic inflammation.1 Although the long-term consequences of COVID-19 are poorly understood, preliminary CT evidence suggests permanent structural damage2 may reduce lung function in some survivors. Oscillometry and multiple breath washout (MBW) may be well suited to detecting small airway abnormalities due to increased sensitivity to heterogeneous small airway and alveolar tissue abnormalities compared to spirometry.3,4 Likewise, inhaled 129Xe MRI provides a unique, quantitative measures of airway and alveolar structure/function through ventilation defect percent (VDP) and the apparent diffusion coefficient (ADC).5 We hypothesized that 129Xe MRI, oscillometry and MBW would reveal abnormal findings in the absence of abnormal pulmonary function test results in COVID-19 survivors. METHODS: Participants with a positive COVID-19 test that were being followed for long-term sequelae provided written informed consent up to three months post-recovery to 129Xe MRI, MBW, oscillometry and spirometry. Ventilation defect percent (VDP) and ADC were calculated using semi-automated segmentation tools.6 Significant differences were determined using paired-sample t-tests. RESULTS: Participants without prior history of chronic respiratory disease (n=8), those with a prior diagnosis of COPD (n=2) and asthma (n=4) were recruited. Mean FEV1 was normal with no post-bronchodilator (post-BD) response (pre-BD=88±19%pred, post-BD=88±20%pred, p=.87), however MBW lung clearance index (LCI) significantly increased (pre-BD=130±46%pred, post-BD=153±47%pred, p=.02). 129Xe MRI VDP was abnormal (pre-BD=7±7%, post-BD=6±5%, p=.46) while ADC (0.052±0.003cm2/s) was similar to values previously evaluated in participants with COPD.7,8 Airway resistance (pre-BD=0.85±0.69, post-BD=0.56±0.72 cmH2O·s/L, p=.010) and reactance (pre-BD=14±13 cmH2O/L, post-BD=9±9 cmH2O/L, p=.036) significantly improved post-BD, were elevated, and similar to previously reported asthma and COPD values.9 No significant post-BD differences were observed between participants with and without obstructive diseases. CONCLUSIONS: Abnormal ADC and VDP in symptomatic participants after COVID-19 recovery were consistent with small airway and alveolar damage. Abnormal oscillometry measurements improved post-bronchodilator, suggesting small airway damage and decreased tissue elastance. An unexpected increase in LCI post-bronchodilator warrants further investigation and may be due to preferential bronchodilator response in certain airways. 129Xe MRI, oscillometry and MBW measurements detect lung function impairment in survivors and may provide useful measures for longitudinal monitoring and treatment response.

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