Introduction

In order to determine the degree of alteration in the ventilatory response to exercise in post-COVID-19 patients compared to healthy controls (CTL), we investigated the VE vs VCO2 slope (VE/VCO_2sl), the membrane (Dm) and capillary (Vc) component of pulmonary diffusion capacity thought Double-Gas diffusion (DLNO/CO) at rest and after submaximal exercise.

Method

Twenty non-hospitalized COVID-19 patients (4±2 months post-infection) and their CTL, matched by BMI and age, underwent; quality of life questionnaires (QOL), 6-minute walk test (6MWT), lung function, DLNO/CO at rest and after 10 minutes of cycling at 85% of the maximum heart rate measured during the 6MWT. Moreover, the ten COVID-19 patients who met the definition of long-COVID underwent cardiopulmonary exercise testing.

Results

QOL, 6MWT, lung function and DLNO/CO at rest and submaximal exercise did not show any differences between the groups. However in long COVID (N=10), the exercise-induced increase of Dm (14±4ml/min/mmHg, p<0.01) and predicted alveolar volume (5±3%, p<0.05) was greater in long COVID patients vs CTL (respectively: 7±5ml/min/mmHg and 1±3%).

The VE/VCO_2sl was higher in long COVID than CTL (32±5 vs 26±2, p<0,05) and correlated with the exercise-induced increase of Vc (6±7ml: r=0.639, p<0.05).

Conclusion

Patients having long COVID infection may however show a persistent larger increase in Dm  during submaximal exercise to reach the same value of Dm than controls what suggest altered diffusion capacity.Patients with long COVID exhibited an altered ventilatory efficiency at exercise that may request a greater increase in pulmonary diffusion for the same level of submaximal effort.