Severity does not impact on exercise capacity in COVID-19 survivors

Background: current data on the impact of acute illness severity on exercise capacity and ventilatory efficiency of COVID-19 survivors, evaluated at cardiopulmonary exercise test (CPET), are limited. Methods: in this post-hoc analysis of our previous observational, prospective, cohort study on mechanisms of exercise intolerance in COVID-19 survivors, we aimed at evaluating the impact of acute COVID-19 severity on exercise capacity, pulmonary function testing (PFT) and chest computed tomography (CT) outcomes. Results: we enrolled 75 patients (18 with mild-to-moderate disease, 18 with severe disease, and 39 with critical disease). Mean (standard deviation - SD) follow-up time was 97 (26) days. Groups showed a similar PFT and CT residual involvement, featuring a mildly reduced exercise capacity with comparable mean (SD) values of peak oxygen consumption as percentage of predicted (83 (17) vs 82 (16) vs 84 (15), p = 0.895) among groups, as well as the median (interquartile range - IQR) alveolar-arterial gradient for O-2 in mmHg at exercise peak (20 (15-28) vs 27 (18-31) vs 26 (21-21), p = 0.154), which was in the limit of normal. In addition, these patients featured a preserved mean ventilatory efficiency evaluated through the slope of the relation between ventilation and carbon dioxide output during exercise (27.1 (2.6) vs 29.8 (3.9) vs 28.3 (2.6), p = 0.028), without a clinically relevant difference. Conclusions: Disease severity does not impact on exercise capacity in COVID-19 survivors at 3 months after discharge, including a ventilatory response still in the limit of normal.