Introduction: Veno-venosus extracorporeal membrane oxygenation (V-V ECMO) used to support severe COVID-19 cases may have long-term respiratory consequences. However, the degree of deterioration in the respiratory mechanics 6 months after the application of V-V ECMO has not been characterized.

Methods: COVID-19 patients underwent V-V ECMO (n=9, ECMO group) were evaluated 4-6 months after hospital discharge. Forced oscillation technique was applied to measure the respiratory resistance (R5) and reactance at 5 Hz (X5) to characterize the resistive and elastic properties of the respiratory system. The difference in the resistance measured at 5 and 19 Hz (R5-19) as an index of small airway heterogeneity was also assessed. A control group (n=9, C group) matched in age, weight, height and gender were also measured in an identical manner.

Results: The anthropometric data did not differ between the protocol groups. Significantly lower X5 was obtained in the ECMO group than in the H group (-1.33±0.14[mean±SE] vs. -0.85±0.1 cmH2O.s/l, p<0.02), which was associated with significantly higher R5-19 in the ECMO group (0.41±0.09 vs. 0.079±0.08 cmH2O.s/l, p<0.02). There was no difference in R5 between the groups.

Conclusions: The decreased X5 in the ECMO group reflect restrictive changes in the lung parenchyma 6 months after severe COVID-19 pneumonitis. The enhanced small airway heterogeneity was also evidenced by the elevated R5-19 in the COVID group, suggesting persistent development of small airway dysfunction even several months after hospital discharge. Our findings highlight the importance of the follow-up of the patients requiring ECMO therapy to support severe COVID-19.