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In medicine, platypnea refers to shortness of breath (breathlessness) that is relieved when lying down, and worsens when sitting or standing up. It is the opposite of orthopnea. The word is derived from the Greek ''platus'' (= flat) and ''pnoia'' (=breath). 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.〔http://circ.ahajournals.org/content/105/6/e47.full〕〔http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1729301/〕 ==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). Insufficiency of abdominal muscles causes lower diaphragm position and breathlessness. In supine position, abdominal organs push the diaphragm in its normal, upper position, reducing the respiratory effort. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Platypnea」の詳細全文を読む スポンサード リンク
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