Cardiopulmonary Exercise Testing in Children With Long COVID: A Case-controlled Study

Background: Cardiopulmonary exercise testing (CPET) is a noninvasive and nonexpensive diagnostic tool, that provides a comprehensive evaluation of the pulmonary, cardiovascular, and skeletal muscle systems' integrated reactions to exercise. CPET has been extensively used in adults with Long COVID (LC), while the evidence about its role in children with this condition is scarce. Methods: Prospective, case-controlled observational study. Children with LC and a control group of healthy children underwent CPET. CPET findings were compared within the 2 groups, and within the LC groups according to main clusters of persisting symptoms. Results: Sixty-one children with LC and 29 healthy controls were included. Overall, 90.2% of LC patients (55 of 61) had a pathologic test vs 10.3% (3/29) of the healthy control. Children with LC presented a statistically significant higher probability of having abnormal values of peak VO2 (P = 0.001), AT% pred (P <0.001), VO2/HR % (P = 0.03), VO2 work slope (P = 0.002), VE/VCO2 slope (P = 0.01). The mean VO2 peak was 30.17 (+/- 6.85) in LC and 34.37 (+/- 6.55) in healthy patients (P = 0.007). Conclusions: Compared with healthy controls, children with LC have objective impaired functional capacity (expressed by a low VO2 peak), signs of deconditioning and cardiogenic inefficiency when assessed with CPET. As such, CPET should be routinely used in clinical practice to objectify and phenotype the functional limitations of children with LC, and to follow-up them.