Differential pulmonary functional recovery from severe COVID-19 and impaired diffusion function in recovered severe COVID-19 patients
Among the 64 patients with pulmonary functional test, 39 ( 60.9% ) were males and 25 ( 39.1% ) were females, with an average ( 49.31 ± 14.98 ) years old, 20 cases ( 31.3% ) of smokers. There were 20 cases ( 31.2% ) with pulmonary ventilation dysfunction, including 15 cases ( 23.4% ) with restrictive ventilation dysfunction and 5 cases ( 7.8% ) with obstructive ventilation dysfunction ; and 23 cases ( 35.9% ) with diffusion dysfunction ( Table 3 ) . Table 3 showed a significant difference in ventilation dysfunctions among the different groups of severity, for restrictive ventilation, which accounted for 0% in mild illness, 16.1% in moderate and 43.5% in severe group, respectively ( p=0.028 ) in moderate and severe groups; for obstructive ventilation dysfunction, which accounted for 30% in mild illness, 6.45% in moderate and 0% in severe group, respectively ( p=0.022 ) in mild and severe groups; Similarly, diffusion dysfunction was observed among different groups, which accounted for 30% in mild illness,22.6% in moderate and56.5% in severe group, respectively ( p=0.021 ) in moderate and severe groups. Small airway function accounted for 40% in mild illness, 41.94% in moderate and 30.43% in severe group, respectively ( p=0.678 ) ( Table 3 ) . This trend of the gradual decrease in level of DLCO among patients was identical with the varying degree of severity. In the severe group, DLCO% pred was ( 78.93 ± 17.48 ) %, which was lower than the average of the three groups, indicating that the diffusion dysfunction in the severe group is more significant. The pulmonary dysfunction of the three groups was statistically significant ( P<0.05 ) ( Table 3 and Figure 1 ) .The value of TLC % pred in severe group was much less than that of moderate or mild groups, suggesting the higher impairment of lung volume in severe COVID-19 patients. Thus, the difference in diffusion dysfunction is statistically significant between the moderate group and severe group, especially the diffusion dysfunction was decreased in the severe group.
Male was positively correlation with diffusion dysfunction and the oxygen therapy was mildly correlated with diffusion dysfunction in severe patients
In order to explore the factors correlation with the decrease in the diffusion dysfunction in all the convalescent COVID-19 patients, the pulmonary function of 56 cases were divided into 5 groups: 0 ) completely normal; 1) diffusion dysfunction; 2) obstruction ventilatory dysfunction; 3) restrictive ventilatory dysfunction; 4) obstruction ventilation dysfunction and diffuse dysfunction. We observed no significant association of age, smoking, comorbidities and oxygen therapy with diffusion impairment. Male has the more risk factor with impaired diffusion impairment (P = 0.037, Table 4).
Further, the pulmonary function of 18 severe cases were divided into two groups with the decrease in the diffusion dysfunction. There were no significant association of age, smoking, comorbidities, hormone, antiviral, convalescent plasma and immunoglobulin with diffusion impairment. The oxygen therapy has the mild correlated with impaired diffusion in severe patients (P=0.040, Table 5).