Investigating the relationship between minute ventilation and metabolic contribution in long COVID: A retrospective cohort study utilizing cardiopulmonary exercise testing

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Long COVID (LC) presents as a complex and debilitating condition characterized by persistent, episodic symptoms that significantly impact individuals' quality of life and functional capabilities (Brown et al., 2021, BMJ Glob Health, 6). There are several hypotheses for the underlying pathophysiology and mechanisms of long COVIDs nature. This study aims to explore the association between minute ventilation and metabolic contribution in individuals experiencing long-term COVID-19 symptoms. Utilising cardiopulmonary exercise testing (CPET), acknowledged as precise, non-invasive prognostic tools, to evaluate cardio-respiratory response to incremental exercise, aiding in the assessment of impaired cardio-respiratory function and perfusion. A cohort observation study was conducted, involving patients with confirmed COVID-19 diagnoses and persistent symptoms three months post-infection, aged between 18 to 65 years. Patients undergo three visits at the university: a baseline assessment, followed by two sessions involving the CPET, spaced 24 hours apart. The baseline visit includes gathering anthropometric data, lung function tests (MIP/MEP), questionnaires, symptom profiling and functional capacity assessments (6MWT and TUG). Data from these assessments determine CPET starting loads based on three stratas: Strata I (6MWD < 350 m, starting load of 10 W), Strata II (6MWD 350-400 m, starting load of 20 W), and Strata III (6MWD > 400 m, starting load of 30 W). Subsequent sub-maximal CPET sessions are conducted to test integrated physiological responses to exercise while preventing PEM/PESE. Measurements include pulmonary gas exchange, ventilation, ventilatory thresholds, and blood profiling. Analysis at present is ongoing. No adverse events or serious adverse events occurred during data collection. Results from this investigation provide insights into the physiological mechanisms underlying long COVID and contribute to the development of tailored management strategies for affected individuals. CPET is the gold standard for assessing cardiorespiratory fitness (CRF) and is vital for understanding LC treatment (Faghy et al., 2024, Prog Card Disease). The use of 2-day CPET methods are increasingly used to identify aerobic deficits and physiological deficits in chronic diseases like ME/CFS and LC. Despite risks, CPET measurements offer insight into pulmonary-vascular function and CRF impairment post-COVID-19 infection (Faghy et al., 2020, Brit J Anaes, 125, 447-449).