Platypnea or platypnoea is shortness of breath (dyspnea) that is relieved when lying down, and worsens when sitting or standing upright.
[2] A related condition, orthodeoxia, describes the clinical finding of low oxygen saturation in the upright position, which improves when lying down.
[3] Platypnea and orthodeoxia (low oxygen levels when in upright posture) can co-exist, and this combination is named platypnea-orthodeoxia syndrome.
[4] Platypnea is usually due to either hepatopulmonary syndrome or an anatomical cardiovascular defect increasing positional right-to-left shunting (bloodflow from the right to the left part of the circulatory system) such as a patent foramen ovale.
[citation needed] The word platypnea uses combining forms of platy- + -pnea, from Greek platus (= flat) and pnoia (=breath).