LAUSR

technologies (including accelerometry) as a source of endpoints in PAH.We used a “low-tech,” generalizable approach but required a companion, equipment, and guidance from coordinators. Our results may have been subject to selection bias and may be applicable only to stable low-risk patients, given the average 6MWD (1). Although only one subject had a related adverse event, the safety of this approach needs to be confirmed in a larger study. Social facilitation and the Hawthorne effect, which can alter task completion results when subjects are aware of being observed (9), may have contributed to our findings. Although the difference was not significant, we noted some variation by site (remote 6MWDwas higher or lower compared with in-clinic distance; Figure 1A); Philadelphia and Providence are in the Northeast, with small differences in terrain, climate, and urban, suburban, and rural communities. Recruitment spanned seasonal changes at both sites (October 2020 to August 2021). Although our results require replication in additional settings, we conclude that remote 6MWTsmay be feasible and valid in stable patients with PH. In masked patients with reductions in the in-clinic 6MWD, it may be reasonable to repeat their studies unmasked while taking appropriate infection prevention precautions.