Application of CT pulmonary function imaging in convalescent COVID‑19 patients

ABSTRACT

Objective To explore the application value of CT pulmonary function imaging in patients with Coronavirus Disease 2019 (COVID‑19) in the convalescent phase. Methods The COVID‑19 patients who were clinically cured and discharged from Union Hospital, Tongji Medical College, Huazhong University of Science and Technology were prospectively collected from January to April 2020. Clinical pulmonary function tests (PFTs) and CT pulmonary function imaging were performed 3 months after discharge. The Philips IntelliSpace Portal image post‑processing workstation was used to obtain the paired inspiratory‑expiratory CT quantitative indexes of the whole lung, left lung, right lung and five lobes. The patients were divided into two groups according to whether residual lesions remain in inspiratory CT images non‑residual lesion group and residual lesion group. The chi‑square test was used to compare the differences in the PFT results between groups;the Mann‑Whitney U test was used to compare the differences in PFT indexes [forced expiratory volume in the first second as percentage of predicted value (FEV1%), FEV1/forced vital capacity (FEV1/FVC), total lung capacity as percentage of predicted value (TLC%), FVC% ] and the differences in quantitative CT indexes [lung volume (LV), mean lung density (MLD), volume change in inspiratory phase and expiratory phase (∆ LV)] between groups. Multiple linear regression was used to analyze the relationship between CT pulmonary function imaging and PFT indexes of convalescent COVID‑19 patients. Results Of the 90 patients with COVID‑19, 35 were males and 55 were females;45 were included in the non‑residual lesion group and 45 were included in the residual lesion group. Fifty‑three patients had clinical pulmonary dysfunction 3 months after discharge, including 22 patients in the non‑residual lesion group and 31 patients in the residual lesion group. In patients with residual disease, left lower lobe and right lower lobe LV, left lower lobe and right lower lobe ∆ LV in the inspiratory and expiratory phase were smaller than those without residual disease;whole lung, left lung, right lung, left upper lobe, left lower lobe and right lower lobe MLD in the inspiratory phase and left lower lobe and right lower lobe MLD in the expiratory phase were greater than those without residual disease (P<0.05). Since there was no significant difference in FEV1/FVC and FVC% between residual and non‑residual lesion groups (P>0.05), FEV1/FVC and FVC% of two groups were combined. Multiple linear regression analysis showed FEV1/FVC= 91.765-0.016×LVin‑right middle lobe+0.014×MLDex‑left lower lobe (R2 =0.200, P<0.001), FVC% =-184.122-0.358× MLDin‑right lung-0.024× ∆ LVleft upper lobe (R2 =0.261, P<0.001). There was significant difference in TLC% between residual and non‑residual lesion groups (P<0.05), so multiple linear regression analysis was performed both in the two groups. In the non‑residual lesion group, TLC% =80.645+0.031× (R2 =0.132, P<0.001);In the residual lesion group, TLC% =-110.237-0.163× LVex‑right lower lobe MLDin‑right upper lobe-0.098×MLDex‑left upper lobe -0.025×LVex‑right lower lobe (R2 =0.473, P<0.001). Conclusion CT pulmonary function imaging can quantitatively analyze the whole lung, unilateral lung and lobulated lung, thus reflecting the regional pulmonary function, providing more valuable diagnostic information for the assessment of ulmonar function in convalescent atients with COVID‑19