Impact of face masks on the 6-minute walk distance in pulmonary hypertension patients during the COVID-19 pandemic: a prospective, randomised cross-over study.

In patients with pulmonary hypertension (PH) or with other pulmonary or cardiac diseases, the 6-minute walking test – accompanied by the Borg dyspnea score – is frequently utilised as a semi-quantitative measure of exercise capacity [1]. The 6-minute walking distance (6 MWD) also serves as primary or key secondary endpoint in numerous clinical trials assessing the efficacy of pharmacotherapies in various forms of PH [2, 3]. Furthermore, the 6MWD is among the key non-invasive measures of multi-modal risk assessment in pulmonary arterial hypertension (PAH) [4–6]. In this context, cut-off values of 440 m and 165 m have been validated to indicate low, intermediate and high mortality risk, respectively, in the 3-strata model proposed by the current ESC/ERS guidelines [1], with an additional cut-off of 320 m to discriminate between intermediate-high and intermediate-low risk in the recently introduced 4-strata approach [7, 8].