Described herein are passive nasal respiratory devices, in particular, passive nasal respiratory devices configured to achieve positive end-expiratory pressure (PEEP) in a subject wearing the device. PEEP devices may have a threshold pressure for opening during expiration. These devices may include a flap valve that opens on inhalation nested with a spring valve that opens when exhalation pressure exceeds a predetermined threshold. The device may be configured to be comfortably worn by a sleeping subject.
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