Cardiopulmonary exercise testing in patients with COVID-19 at 3 months from hospital discharge

ABSTRACT

Aims The long-term COVID-19 effects are currently unknown. Whether and for how long symptoms extend beyond the acute phase of the disease is unresolved. Aim of this study was to determine the functional capacity of COVID-19 survivors by cardiopulmonary exercise testing (CPET) and describe its association with dyspnoea, the most frequent symptom after discharge from a tertiary care hospital. Methods and results All COVID-19 patients discharged from our tertiary care institution were enrolled in a prospective follow-up study which would assess clinical, instrumental and laboratory characteristics of COVID-19 survivors at 3 months from hospital discharge (i.e. long-covid). To limit bias in dyspnoea quantification, patients hospitalized in residential care facilities with severe cognitive impairment/disability, ischaemic cardiopathy, and/or heart failure and severe respiratory disease (i.e. chronic obstructive pulmonary disease) were excluded. Clinical evaluation included peripheral blood samples including inflammatory cytokines, pulmonary function testing (functional respiratory and 6 min-walking test), lung ultrasound, ECG recording, and a comprehensive echocardiographic exam. All patients with peripheral oxygen desaturation at 6 min-walking test (SpO2 < 92%), dyspnoea and with a history of hospitalization in critical care settings were referred for CPET. Dyspnoea was classified with the Medical Research Council (MRC) scale. From June 2020 to May 2021, 198 patients were enrolled;overall, 42% of patients presented with dyspnoea at 3 months from hospital discharge with no difference according to disease severity on hospital admission (P = 0.233). Clinical, laboratory, and echocardiographic parameters were similar between patients with and without dyspnoea. At CPET, 61% of patients complaining dyspnoea showed a %peak VO2 lower than 85% of the predicted value, associated with a lower exercising tolerance and duration and with a globally reduced equivalent metabolic load (METS 5.3 ± 1.2 vs. 6.6 ± 1.6, P = 0.003). Mean anaerobic threshold was lower for symptomatic patients (46 + 13 vs. 50 + 10, P = 0.03). At multivariable logistic regression analysis, after adjustment for age, number of comorbidities, and body mass index, only %peak VO2 (HR 0.973;95% CI 0.948–0.998) and male gender (HR 0.548;95% CI 0.328–0.999) were associated with dyspnoea. Conclusions At 3-months, almost 1-in-2 patients discharged for COVID-19 pneumonia presented with dyspnoea, irrespective of disease severity. Among patients undergoing CPET, only %peak VO2 and gender were associated with symptoms suggesting a potential systemic inflammatory-mediated response and important gender related differences for the long-covid.