ABSTRACT
Background: Many patients recovered from COVID-19 infection present a variety of symptoms which limits overall quality of life, as reduced exercise performance, dysfunctional breathing, cough, dyspnea, weakness and anxiety. This condition has been named long COVID. The origin of this symptomatology is still unclear. This study has the aim to analyse the relation between symptoms and respiratory function, focusing on the alveolar capillary membrane. Method(s): Consecutive patients with long COVID 19 symptoms after 6 months were included. Patients underwent full clinical evaluation, laboratory tests, echocardiography, thoracic CTscan, spirometry including alveolar capillary membrane diffusion by means of combined carbon dioxide and nitric oxide lung diffusion (DLCO/ DLNO) and cardiopulmonary exercise test. We measured surfactant derive protein B (immature form) as blood marker of alveolar capillary function. A questionnaire allowed to evaluate symptoms. Result(s): We evaluated 204 post COVID-19 patients (age 56.5+/-14.5 y, 89 females (44%), BMI 25.7+/-4.0, 6% active smokers) referring to our hospital 171+/-85 days after the end of acute COVID-19 infection (Fig. 1). None of spirometry data was associated with long COVID 19 referred symptoms. SPB was not associated to differences in any of the referred symptoms. Subjects with lower capillary volume (VCap) have more frequently dyspnea, tiredness, fatigability and hair loss (Fig.2). CT scan lung damage correlated with SPB and membrane diffusion but not with VCap, exercise performance or VE/VCO2 slope. The strongest correlation of SPB were with lung parenchyma damage and Vcap. Conclusion(s): Our data suggest that a relevant reduction of alveolar capillary membrane function plays a central role in the long COVID cardiorespiratory symptoms. (Figure Presented).