Platypnea or platypnoea is shortness of breath (dyspnea) that is relieved when lying down, and worsens when sitting or standing. It is the opposite of orthopnea. The condition was first described in 1949 and named in 1969. A related condition, orthodeoxia, describes the clinical finding of low oxygen saturation in the upright position, which improves when lying down. Platypnea and orthodeoxia can co-exist, and this combination is named platypnea-orthodeoxia syndrome. The syndrome is considered extremely rare.