Fig. 1.

Participant flow diagram. Due to discomfort related to the procedures, N = 2 COVID-19 patients aborted the study before completing any breath-hold, N = 5 did not complete maximal breath-holds, leaving 50/57 with available data. N = 1 control could not complete any breath-holding. We note that (exploratory) re-inclusion of the N = 5 patients who had available mean desaturation data (but not maximal duration variables) had no meaningful impact on the associations between mean desaturation and adverse outcomes. Patients who met the criteria for the adverse primary composite outcome are denoted “VS + ” (N = 4 non-invasive bi-level pressure support, N = 7 intensive care, N = 1 death; “VS − “ indicates patients discharged without meeting adverse primary outcome criteria