Cardiopulmonary exercise testing in patients with long covid

ABSTRACT

ObjectiveExamine the relationship between symptoms and exercise physiological parameters in patients with long covid.MethodsPatients with long covid symptoms 6–12 months after covid19 infection referred to the long covid clinic were invited for Cardiopulmonary Exercise Testing (CPET). None had required ventilatory support during covid19 infection. All patients had normal transthoracic echocardiograms and normal resting flow-volume curves and gas transfer measurements. All patients underwent standard cycle ergometer symptom-limited CPET. Treatment guided by the CPET was offered and follow-up CPET was performed at 3 months.Results32 patients had a first CPET. The commonest symptoms were breathlessness (30/32), fatigue (26/32), cough (7/32), ‘brain fog’ (6/32) and chest pain (5/32). The main CPET physiological abnormalities were a borderline low peak oxygen uptake (mean 82.5% predicted), a low anaerobic threshold (AT, mean 47.6% of predicted maximal oxygen uptake) and a low oxygen uptake/work rate slope (mean 9.4 ml/min/W). The oxygen pulse curve flattened early in exercise, but peak oxygen pulse was normal (mean 88.9%).20 patients underwent a second CPET. 14 patients had improved symptoms breathlessness (11/20), fatigue (9/20), cough (2/20), ‘brain fog’ (3/20) and chest pain (0/20). Symptom improvement was associated with a rise in peak oxygen uptake (to mean 85.3% predicted) and oxygen pulse (to mean 94.1% predicted) although both remained within the normal range. The AT remained low (mean 46.4% predicted maximal oxygen uptake). The ventilatory equivalent for carbon dioxide (VE/VCO2) was normal 28.6 L/L at AT.6 patients with unchanged symptoms had a reduction in oxygen pulse to mean 81.5% predicted compared to the first CPET but a rise in VE/VCO2 to 33.7 L/L at AT.ConclusionsLong covid is associated with impaired peak oxygen uptake, AT and oxygen pulse. This suggests an oxygen delivery or uptake disorder or deconditioning. The transthoracic echocardiograms were normal suggesting a disorder at the muscle level.A targeted treatment programme based on CPET improves symptoms and physiological parameters in long covid patients.Patients with unchanged symptoms after 3 months of treatment had persistent physiological abnormalities but appeared to develop features of dysfunctional breathing syndrome.