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.
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A related condition, orthodeoxia, describes the clinical finding of low oxygen saturation in the upright position, which improves when lying down.
Platypnea and orthodeoxia often co-exist, and this combination is named platypnea-orthodeoxia syndrome. The syndrome is considered extremely rare.
Causes
Platypnea is 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). These defects include rare syndromes in which the venous blood from the liver does not pass through the lungs, or if venous blood from the portal circulation reaches the inferior vena cava without passing through the liver (Abernethy malformation, type 1).
Etymology and pronunciation
The word platypnea uses combining forms of platy- + -pnea, from Greek platus (= flat) and pnoia (=breath). See pronunciation information at dyspnea.