Figure 1.

Schematic of study treatment and testing. Upon hospital admission, subjects underwent a physical examination, mini-mental state examination (MMSE), a separate, detailed neurologic examination, 12-lead electrocardiogram (ECG), pulmonary function testing, and baseline laboratories. Subjects were then acclimated to high-flow nasal cannula (HFNC) for 4 hr, after which they were exposed to hydrogen gas (H2) for up to 72 hr. Subjects were regularly screened for signs and symptoms, which were graded according to the Common Terminology of Clinical Adverse Events (CTCAEs). Following exposure, measurements were repeated prior to discharge. A follow-up phone call took place at 24 hr and 3–5 d following discharge.