Dear Editor
We read with great interest the article by Clavario et al. [1] concerning the application of the cardiopulmonary exercise testing (CPET) in a large cohort of COVID-19 patients at 3 months follow-up. Reading CPET variables, we note that the authors do not report data about ventilatory limitation, although values of ventilatory equivalent for carbon dioxide (VE/VCO2), as described in the methods of the supplementary data, have been determined.
In our pilot study, in post-COVID subjects (6-months follow-up) in which we have excluded baseline confounders (age > 65 years, moderate obesity, chronic respiratory failure or need for oxygen-therapy under exertion, concomitant previous respiratory or non-respiratory diseases), we performed the CPET [2]. Although our 28 subjects had a normal lung function and a preserved maximal exercise capacity, we found that 8 subjects (29%) had exercise ventilatory inefficiency (EVin), using the regression equation of VE/VCO2 slope for healthy subjects, according to Sun et al. [3]. Moreover, subjects with EVin showed a reduction of heart rate (HR) recovery and VE/VCO2 slope was inversely correlated with HR recovery. Therefore, we concluded that the exercise ventilatory inefficiency related to lower heart rate recovery may be a sign of systemic alterations present in the post-disease phase of these subjects.
We believe it may be interesting to have some data about the exercise ventilatory inefficiency in a different timing and in a larger cohort of post-COVID survivors, with also associated comorbidities.
Declaration of Competing Interest
The authors report no relationships that could be construed as a conflict of interest.
References
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