Abstract: In some embodiments, a rebreathing oxygen supplementation device includes an enclosure including an internal surface of a size and shape to entirely cover the nasal region of a patient and including an edge region of a size and shape to reversibly mate with a skin region of the patient surrounding the nasal region. The device can include at least one tubular structure affixed to the enclosure, the tubular structure including a proximal region with a first aperture positioned adjacent to a nostril of the patient and at least one distal region with a second aperture, the tubular structure positioned to permit gas flow between an interior of the enclosure and a region exterior to the tubular structure, and an aperture in the proximal region positioned adjacent to the patient's nostrils.