Coronaltitude - Multicentric Evaluation of the Impact on Hypoxia Sensitivity of Patients With COVID-19

In this study, the investigators will examine the extent to which having suffered coronavirus disease 2019 (COVID19) impacts one's sensibility to hypoxia by means of the 'Richalet test'. The aim of the study is to formulate recommendations for advice in altitude mountain medicine for patients having suffered COVID19. To determine any eventual changes in response to hypoxia, performances by participants having suffered COVID-19 and participants having stayed free of COVID-19 will be both compared intra-individually with previous performances (pre-COVID-19 pandemic) and between both groups of subjects. The investigators hypothesize that patients having suffered COVID19 might perform differently on the cardiopulmonary exercise test compared to before the illness. Based on recent research on COVID19 pathophysiology and -patient follow-up, it might be expected that COVID19 alters the response to hypoxia, thus influencing one's acclimatization capabilities at high altitude, albeit reversibly and/or temporarily. Different alterations of response to hypoxia could be observed. The virus causing COVID19, the "severe acute respiratory syndrome coronavirus 2" (SARS-CoV-2), has the potential to significantly damage the nervous system and to affect cardiorespiratory functions. If SARS-CoV-2 does, similarly to MERS and SARS, induce cardiorespiratory and neurological dysfunction, then COVID19 patients may have impaired hypoxia response after infection and perform worse on the 'Richalet test' in comparison to before the illness. Conversely, reports of high prevalence of dyspnea in patients up to 3 months after SARS-CoV-2 infection, might indicate infection-induced degenerative changes in the carotid bodies, which might lead to sensibilization of the peripheral chemoreceptors to impaired oxygenation. Possibly similar to the impact of aging and smoking on the cardiorespiratory response to hypoxia, this phenomenon of sensibilization could entail an increased hypoxic response in patie