Cardiopulmonary Exercise Testing in Patients With Long COVID Evaluating Functional Capacity and Exercise Limitations

Background After COVID-19, some patients present with ongoing symptoms (eg, breathlessness, exercise limitations), even after mild acute infection. Research Question What is the exercise capacity of patients diagnosed with long COVID and does it change from baseline to 1-year follow-up? Study Design and Methods This retrospective case series included patients with persistent symptoms after a confirmed diagnosis of COVID-19. Exercise capacity was examined by cardiopulmonary exercise testing (CPET), and parameters related to performance, ventilation, circulation, and gas exchange were compared with predicted values. A subgroup of patients was retested 1 year after baseline, and self-reported physical fitness was assessed at follow-up. Results In total, 169 patients completed baseline CPET and 41 patients completed 1-year follow-up. Mean maximum workload was 172 W (95% CI, 161-182), with 19% not achieving at least 84% predicted workload. Mean peak oxygen uptake was 24.4 mL/kg/min (95% CI, 23.1-25.7), and 36% had a value below % predicted. Oxygen uptake/workload slope below the normal threshold of 8.4 mL/min/W was observed in 54% of patients. The 1-year follow-up results showed no statistically significant changes in any of the CPET parameters, which correspond to lack of improvement in self-reported physical fitness. Interpretation Patients with long COVID demonstrated lowered peak oxygen uptake, oxygen uptake/workload slope, and/or ventilatory equivalent for carbon dioxide, but different parameters were lowered in different patients, illustrating a heterogeneous study population. No improvements in any parameters were found at 1-year follow-up.