Clinicians should be aware that POS may mimic POTS. In patients presenting with platypnea, measurement of oxygen saturation in the supine and standing positions should be performed. A measurable drop in arterial oxygen saturation of > 5% should prompt further investigation with analysis of supine and standing arterial blood gases as well as testing for intracardiac shunts and lung or liver disease. If an intracardiac anatomical defect is present, the condition is potentially curable with surgical intervention.
