From the Guidelines
Orthodeoxia, also known as platypnea, is a condition characterized by worsening hypoxemia when upright, typically presenting as shortness of breath that worsens when standing and improves when lying down. This condition is often associated with pulmonary arteriovenous malformations (PAVMs), which are abnormal connections between the pulmonary artery and pulmonary vein that bypass the intervening pulmonary capillary bed, leading to impaired gas exchange and filtration of the systemic venous return 1. The clinical manifestations of PAVMs, including orthodeoxia, depend on the size, number, type, and flow through the malformations, with most patients being asymptomatic, but some experiencing hypoxemia, transient ischemic attacks, and cerebral strokes 1.
Some key points to consider in the diagnosis and management of orthodeoxia include:
- Measuring oxygen saturation in different positions to identify positional changes in breathing difficulty
- Using echocardiography, CT scans, or pulmonary function tests to identify the underlying cause, such as PAVMs or intracardiac shunts
- Targeting treatment at the specific cause rather than symptoms, which may include surgical closure of cardiac shunts, embolization of arteriovenous malformations, or management of underlying liver or lung disease 1
- Providing supplemental oxygen as temporary relief while awaiting definitive treatment
It is essential to suspect orthodeoxia in patients who experience positional changes in breathing difficulty, especially those with known cardiac or pulmonary conditions, as prompt diagnosis and treatment can significantly improve quality of life and prevent complications from chronic hypoxemia 1.
From the Research
Definition and Characteristics
- Orthodeoxia, also known as platypnea, is a condition characterized by dyspnea and desaturation in the upright position, with improvement of symptoms and blood oxygenation in the supine position 2, 3, 4, 5, 6.
- The syndrome is associated with a right-to-left shunt, usually across a patent foramen ovale, and can be caused by various underlying conditions, including intracardiac and extracardiac abnormalities 3, 6.
Clinical Presentation
- Patients with platypnea-orthodeoxia syndrome often present with dyspnea and hypoxemia in the upright position, which improves or resolves in the supine position 2, 4, 5.
- The clinical presentation can be heterogeneous and may include other symptoms such as psychiatric symptoms, as seen in a case report of a 73-year-old female with posture-dependent hypoxemic-induced psychiatric symptoms 2.
Pathophysiological Mechanisms
- The hypoxia in platypnea-orthodeoxia syndrome is attributed to the mixing of deoxygenated venous blood with oxygenated arterial blood via a shunt 3.
- The primary mechanisms of the syndrome can be broadly classified into intracardiac abnormalities, extracardiac abnormalities, and miscellaneous etiologies 3.
- A patent foramen ovale is the most common reported site of an intracardiac shunt, and other intracardiac shunts can occur through an atrial septal defect or an atrial septal aneurysm 3, 6.
Diagnosis and Treatment
- Diagnosis of platypnea-orthodeoxia syndrome requires a systematic evaluation, including measurement of blood gases in the supine and upright positions, and imaging studies such as echocardiography to identify the underlying cause of the shunt 2, 3, 6.
- Treatment options include percutaneous closure of the patent foramen ovale, as seen in several case reports, and other interventions aimed at addressing the underlying cause of the shunt 2, 4, 5.