Pulmonary function in post-COVID patients underwent veno-venous extracorporeal membrane oxygenation: 1-year follow-up

<bold>Background:</bold> Severe COVID-19 infection may require veno-venous extracorporeal membrane oxygenation (V-V ECMO) support. The residual pulmonary symptoms in patients who have undergone this support are not characterized. Therefore, our aim was to reveal changes in respiratory function over a one-year period in post-COVID-19 patients who required V-V ECMO support. <bold>Methods:</bold> We compared 6-month and 1-year outcomes of patients with severe COVID-19 infection who received V-V ECMO support (n=9). Respiratory oscillometry was used to assess airway properties with 5 Hz resistance reflecting the conducting airways (R₅), and the difference between 5 and 19 Hz resistances characterizing small airway function (R₅-R₁₉). Respiratory tissue elasticity was assessed by the area under 5 Hz resistance curve (AX₅). Carbon monoxide diffusion capacity (DLCO) was also measured. Dynamic respiratory volumes were determined by spirometry and static respiratory volumes by plethysmography. <bold>Results:</bold> Compared to 6 months after hospital discharge, 1-year measurements showed significant improvements in static and dynamic lung volumes and DLCO (18.8±4.3 vs. 21.2±4.1 ml/min/mmHg, p<0.01). A significant increase in R₅ and R₅-R₁₉ (0.41±0.16 vs 0.60±0.22 cmH₂O.s/l, p<0.05) was not associated with a change in AX₅. <bold>Conclusions:</bold> The persistent increase in small airway resistance values indicates a remanent constriction of this compartment in the 1-year post-COVID period. The long-term improvement in lung volumes and gas exchange parameters may indicate an increased presence of recruitable alveoli 1 year after V-V ECMO, highlighting the need for respiratory physiotherapy. Funding: OTKA-NKFIH 138032