Understanding Post-COVID Dyspnea: Clinical and Functional Insights from Long COVID Patients

Objective: Long COVID (LC) has been defined as a chronic condition that occurs after SARS-CoV-2 infection and persists for more than 3 months. Dyspnea is the most common and disabling symptom with several mechanisms identified. The pathophysiology of post-COVID dyspnea is unknown. The aim of this study is to analyze the clinical profile of patients presenting with dyspnea in the context of LC and to assess its possible relation with complementary diagnostic tests. Material and Methods: This is a retrospective cohort study including adult patients diagnosed with LC attending a post-COVID outpatient clinic. Dyspnea was assessed using mMRC and Borg scales. Complementary tests included chest imaging, pulmonary function tests (PFTs) and a six-minute walk test (6MWT). These assessments were performed at several time points throughout follow-up (3, 6, and 12 months). Results: Eighty patients diagnosed with LC were included, the mean age was 60.0 ± 14.4 and 43 (54.8%) were female. Most patients were hospitalized during acute infection (97.5%) and 25 patients experienced respiratory failure. During the follow-up, chest X-rays showed persistent abnormalities in 67.5% of patients, and 6MWT was pathological in 61.3% at 277 days (IQR 176–326) after acute infection. No significant differences were observed in the prevalence of ventilatory failure across dyspnea severity categories. Reduced DLCO was observed in 20% of patients, while obstructive or restrictive patterns were infrequent. Through three follow-up visits, pulmonary function and exercise capacity remained stable, with modest improvements in DLCO and exercise-induced desaturation (p = 0.005). In multivariable analysis, obesity (adjusted OR 7.88; p = 0.023) and lower DLCO (p = 0.049) were independent predictors of more severe dyspnea, highlighting the role of non-pulmonary factors in Long COVID. Conclusions: This study describes the clinical and functional profile of a cohort of patients with LC. Although abnormal findings were frequent, only impaired DLCO and obesity were independently associated with dyspnea severity, while imaging and six-minute walk test abnormalities showed no consistent association with symptom intensity, supporting a multifactorial origin of post-COVID dyspnea.