Long-term effects of severe COVID-19 pneumonia on ventilation-perfusion matching

<bold>Introduction:</bold> In the most severe cases of COVID-19, patients develop acute pneumonia leading to severe gas exchange defects, necessitating veno-venous extracorporeal membrane oxygenation (V-V ECMO) support. While persistent post-COVID pulmonary symptoms are expected in these patients, the long-term ventilation-perfusion mismatch has not been characterized. Therefore, we aimed at assessing these disturbances in post-COVID patients who have received V-V ECMO support. <bold>Methods:</bold> Mainstream volumetric capnography was conducted on post-COVID patients who had undergone V-V ECMO support (COVID group, n=9) one year after their hospital discharge. These results were then compared with data from a matched healthy control group (CTRL group, n=9). The study focused on determining the slopes of the second (S2V) and third (S3V) phases of the capnogram, as well as measuring both the Bohr physiological and Fowler anatomical dead spaces. <bold>Results:</bold> In the COVID group, we obtained a significant decrease in the S2V compared to the CTRL group (193±45 vs. 264±52 mmHg/s, p<0.05) and a significant increase in the S3V (12.1±6.6 vs. 6.7±3.7 mmHg/s, p<0.05). No differences in anatomical or physiological dead space parameters were observed between the study groups. <bold>Conclusion:</bold> An elevation in S3V suggests persistent ventilation-perfusion mismatch one year after hospital discharge following severe COVID-19 pneumonia. Conversely, a diminished S2V may be indicative of compromised small airway function. These findings underscore the importance of long-term pulmonary rehabilitation for patients who have undergone V-V ECMO support due to severe acute viral pneumonia. Funding: OTKA-NKFIH 138032