ObjectiveTo investigate the static pulmonary function and cardiopulmonary exercise function of convalescent patients with coronavirus disease 2019 (COVID-19) after discharge.MethodsPulmonary function and cardiopulmonary exercise capacity of COVID-19 patients who admitted to our hospital from January to March 2020 were analyzed. The patients were divided into a non-critical group (3 cases of moderate illness, 2 cases of severe illness) and a critical group (5 cases of critical illness). Five of the 10 patients completed spirometry on day 14 after discharge. All patients performed spirometry, diffusion capacity and cardiopulmonary exercise test around 28 days post-discharge. Ten healthy subjects were used as a control group.ResultsForced expiratory volume in one second of percent predicted (FEV1%pred), forced vital capacity of percent predicted (FVC%pred), the FEV1/FVC ratio (FEV1/FVC), peak expiratory flow of percent predicted (PEF%pred) and mean forced expiratory flow between 25% and 75% of percent predicted (FEF25%-75%%pred) of COVID-19 group were all within normal ranges, and there were no significant difference between COVID-19 group and the healthy group (P>0.05). Diffusion capacity (the carbon monoxide diffusion capacity of percent predicted, DLCO%pred) decreased in 3 patients. The peak oxygen uptake of percent predicted (PeakVO2%pred), oxygen uptake efficiency slope (OUES), Oxygen pulse of percent predicted (VO2/HR%pred) in COVID-19 group decreased and were statistically significantly lower than the control group (P<0.05), but there was no significant difference in ventilatory equivalents for carbon dioxide at anaerobic threshold (VE/VCO2@AT) and the slope of ventilatory equivalent for carbon dioxide (VE/VCO2 slope) between the two groups (P>0.05). Compared to the non-critical group, the critical group displayed significantly lower FVC%pred and VO2/HR%pred (P<0.05). A decrease in PeakVO2%pred was observed in critical group, but the difference did not reach statistical significance (P>0.05). The FVC%pred and PEF%pred were significantly improved in 5 COVID-19 convalescents on Day 28 after discharge when comparing with day 14 (P<0.05).ConclusionsIn the first month after discharge, recovered COVID-19 patients mainly presented decreased exercise endurance in cardiopulmonary function tests.There are also some survivors with reduced diffusion function, but the impaired lung function of COVID-19 patients might return over time.