<unk>  is a condition in which a person has shortness of breath and low oxygen saturations when upright<unk>  and<unk> , but no symptoms when lying down. It can be caused by ventilation-perfusion mismatch, intracardiac shunting, or pulmonary shunting. In some cases, the cause is multifactorial.
Platypnea-orthodeoxia syndrome
COACH syndrome
Wooden chest syndrome
Inert gas asphyxiation
Oculo-respiratory syndrome
Monofixation syndrome
Thoracic insufficiency syndrome
Upper airway resistance syndrome