Platypnea is a symptom and not a disease, so once found, a careful history and physical examination should focus on finding the underlying disease that may predispose to it.[8] Some of the findings that one should look for include:

• Vital signs in orthodeoxia: Not responding to oxygen administration may be related to the presence of a right-to-left shunt.
• Assessment for spider nevi, palmar erythema, ascites, edema, etc. may be signs of chronic liver disease.
• Heart exam for any murmurs that may suggest a shunt.
• Lung exam for underlying lung disease (exam will vary based on disease, for example, velcro crackles in patients with idiopathic pulmonary fibrosis).

Laboratory tests should be directed to the possible underlying etiology. For example, laboratory studies to evaluate for suspected liver disease.[5]

Echocardiogram with agitated saline bubble study is a very useful initial test to evaluate the presence of intracardiac or extra-cardiac shunts. The appearance of microbubbles in the left atrium during the first 3 beats after opacification of the right chambers suggests an intracardiac shunt whereas the appearance of microbubbles in the left side after more than 3 to 6 beats suggests an extracardiac shunt, for example, an intrapulmonary shunt like in hepatopulmonary syndrome). A Valsalva maneuver may help increase the right-to-left shunting. Other tests to evaluate shunts include a contrast-enhanced echocardiogram, macroaggregated albumin scintigraphy scan, and an invasive angiogram.[9]

Chest plain radiograph may show some underlying lung disease that can explain the platypnea, but this test may not be sensitive.[10]

CT scan in case of suspected lung abnormality may give further details. For example, CT with contrast may show arteriovenous malformations that are causing the right-to-left shunt.

Platypnea is a symptom; therefore, management should be directed toward the underlying disorder. Detailed management of each disease is beyond the scope of this review, but the following measurements apply:

• Supplemental oxygen should be provided to all hypoxic patients.

Examples of managing causative disorders include:

• HPS: The only definitive treatment for cirrhotic patients with HPS is liver transplantation. Supportive management should be provided waiting for transplantation.[11]
• Lung disease: Management depends on the underlying disease, but examples include antibiotics for pneumonia, embolotherapy for large pulmonary arteriovenous malformations and disease-specific treatment for patients with interstitial lung disease.[12]
• Intracardiac shunts: PFO usually does not require any treatment as it may present in up to 25% of people. If the patient is symptomatic with platypnea-orthodeoxia or to prevent paradoxical embolic stroke, then device closure may be an option. Consultation with a cardiologist and cardiovascular surgeon is often required for the management of other intracardiac shunts.[8]

• Hypoxemia

• Intracardiac shunting

• Positional dyspnea

• Pulmonary shunting

• Ventilation-perfusion mismatch

• Platypnea is commonly associated with orthodeoxia and both result from diseases that cause intracardiac or extracardiac right-to-left shunting significant enough to cause hypoxia.
• Measuring oxygen saturation in different positions should be performed any time platypnea is reported.
• Treatment of platypnea is directed to the underlying cause.

• Hepatopulmonary syndrome is defined as the triad of liver disease, pulmonary gas exchange abnormalities leading to arterial deoxygenation, and evidence of intrapulmonary vascular dilatations.[13]Diagnostic criteria for Hepatopulmonary Syndrome consist of the following :[13]

  The presence of liver disease and / or portal hypertension

  An elevated room air alveolar-arterial oxygen gradient {P(A-a)O2 gradient} > 15mmHg or > 20mmHg when age > 65years.

  Evidence of intrapulmonary vascular dilatations in the basal parts of the lungs

  Absence of other significant cardiopulmonary disease.

The diagnosis of platypnea is usually complex and requires a thorough clinical and radiological assessment of the patient. The clinical outcomes depend on identifying the underlying etiology. Coordination of care and early involvement of an interprofessional team that includes a pulmonologist, cardiologist, radiologist, and a respiratory therapist is essential for early diagnosis and targeted treatment.[8] Ideally, the underlying disorder will be treated, thus eliminating the respiratory symptoms. If this is not possible due to the nature of the underlying disorder, clinical management of platypnea must target patient education and symptom management.