Platypnea or platypnoea is shortness of breath (dyspnea) that is relieved when lying down, and worsens when sitting or standing upright. It is the opposite of orthopnea.[1] The condition was first described in 1949 and named in 1969.[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][5] The syndrome is considered extremely rare however.[4]