Importance of Cardiopulmonary Exercise Testing amongst Subjects Recovering from COVID-19

The cardiopulmonary exercise test (CPET) provides an objective assessment of ventilatory limitation, related to the exercise minute ventilation (V-E) coupled to carbon dioxide output (V-CO2) (V-E/V-CO2); high values of V-E/V-CO2 (slope) define an exercise ventilatory inefficiency (EVin). In subjects recovered from hospitalised COVID-19, we explored the methodology of CPET in order to evalu- ate the presence of cardiopulmonary alterations. Our prospective study (RESPICOVID) has been proposed to evaluate pulmonary damage's clinical impact in post-COVID subjects. In a subgroup of subjects (RESPICOVID2) without baseline confounders, we performed the CPET. According to the V-E/V-CO2 slope, subjects were divided into having EVin and exercise ventilatory efficiency (EVef). Data concerning general variables, hospitalisation, lung function, and gas-analysis were also collected. The RESPICOVID2 enrolled 28 subjects, of whom 8 (29%) had EVin. As compared to subjects with EVef, subjects with EVin showed a reduction in heart rate (HR) recovery. V-E/V-CO2 (slope) was inversely correlated with HR recovery; this correlation was confirmed in a subgroup of older, non-smoking male subjects, regardless of the presence of arterial hypertension. More than one-fourth of subjects recovered from hospitalised COVID-19 have EVin. The relationship between EVin and HR recovery may represent a novel hallmark of post-COVID cardiopulmonary alterations.