Cardiopulmonary exercise test 3 to 12 months after COVID-19 hospitalization

Despite recent advances, exercise intolerance in post-COVID-19 patients remains incompletely characterized. <bold>Objectives:</bold> The main objective was to compare pulmonary function tests(PFTs) at rest and during exercise(CPET) between 3-12months after COVID-19 hospitalization. Second, analyze the persistence of reduced aerobic capacity (VO2peak≤80%pred) and their relation to cardiopulmonary sequelae after 12months. Methods: Observational and prospective multicenter FENIX study after COVID-19 hospitalization. Patients underwent PFTs and CPET with earlobe arterialized blood gas analysis. <bold>Results:</bold> 381 patients were evaluated, 60/114 performed CPET after 12months. The mean age was 55±10years, 65% male and 68% in ICU. Comparatively, there were an increase in FVC%pred(p<0.001), TLC%pred(p<0.001), DLCO%pred(p<0.001). At peak exercise, there was an increase in workload(p<0.001), VT(p=0.026) and PaO2(p=0.017), and a decrease of RR/VT(p<0.001) and P(A-a)O2(p=0.005). 38% had reduced VO2peak ≤80%pred. No differences were found in dyspnea (mMRC) and resting PFTs between VO2peak≤80 or >80%pred. During exercise, low peak workload(68±8 vs 95±12W;p<0.001), ∆VO2/WR(p=0.002) and O2pulse(76±26 vs 109±18%pred;p<0.001) were found in VO2peak≤80%pred. No differences were found in ventilatory and gas exchange responses between groups. Conclusion: There was an improvement in resting PFTs and ventilatory and blood gas responses during exercise despite no change in VO2peak between 3-12months after COVID-19, suggesting improvement in lung sequelae during the follow-up. However, the persistence of lower aerobic capacity was related to cardiocirculatory dysfunction, possibly due to low O2 delivery and/or imbalance of O2 muscle utilization.