Introduction: Exercise intolerance is common among patients who suffer from long-term consequences of COVID19 (post COVID-syndrome). In this study, we aimed to assess exercise tolerance in this group by means of cardiopulmonary exercise testing (CPET).

Methods: 74 CPETs of 70 patients were analysed as part of a prospective observational study on clinical sequelae of COVID19 (CCHROMO study). All CPETs included in this analysis were performed between September 2020 and November 2021.

Results: Participants (median age 48 years [IQR 39-55], 62.9% female) had mostly experienced a mild or moderate clinical course of acute SARS-CoV2. Most participants (77.1%) had no known history of chronic pulmonary disease. Median time between diagnosis of COVID19 and CPET was 202 days [IQR 113-276 days].

Maximum oxygen uptake (VO2max[%]) was < 85% of predicted in 22 (29.7%), ventilatory threshold (VT1) was ? 40% in 35 (47.3%) of the 74 CPETs. In a linear mixed model (LMM), time since diagnosis of COVID19 showed a statistically significant effect on VO2max[%] (estimated fixed effect +1.8% per month since diagnosis, p=0.017). Patients with maximum inspiratory pressure (MIP) below reference had on average lower peak oxygen uptake than those with physiological MIP (LMM, estimated fixed effect -380.2 ml/min, p<0.001). Deconditioning or lack of fitness was identified as probable cause in 9 of 22 cases with reduced exercise capacity (40.9%), cardiac limitation in 7 (31.8%), and respiratory limitation in 4 cases (18.2%). In 2 cases (9.1%) no cause could be identified.

Conclusion: Exercise intolerance in PCS is frequently linked to deconditioning and cardiac limitations, and infrequently linked to respiratory limitations.