FLNA and COVID-19: The presence of an association between FMD values and two primary CPET parameters, namely VE/VCO2 slope and PETCO2 at peak, suggests that the alteration of endothelial barrier properties in systemic and pulmonary circulation may be somehow related to the reduced ventilatory efficiency in COVID-19 patients, with our regression models and subgroup analyses supporting the possibility of a potential pathogenic role.