Platypnea is breathlessness that worsens when you sit or stand up and eases when you lie down. That pattern is the exact opposite of the far more common orthopnea, where people with heart failure prop themselves on pillows at night because lying flat makes breathing harder. Platypnea’s counterintuitive nature makes it easy to miss, and when it pairs with a measurable drop in blood-oxygen levels in the upright position, the combination is called platypnea-orthodeoxia syndrome (POS).1PubMed Central. Platypnea-Orthodeoxia Syndrome: Diagnostic Challenge and the Importance of Heightened Clinical Suspicion The underlying cause usually involves blood bypassing the lungs through an abnormal passageway, and pinpointing where that passageway sits is the key to treatment.
Why Sitting Up Makes Breathing Worse
Under normal circumstances, all the blood returning to the right side of your heart gets pumped through the lungs, picks up oxygen, and returns to the left side before heading out to the body. In platypnea-orthodeoxia syndrome, some of that oxygen-poor blood skips the lungs entirely by flowing through a shunt, a hole or abnormal connection that lets it cross directly into the oxygen-rich side of the circulation. The result is a mixture of oxygenated and deoxygenated blood leaving the heart, which lowers your overall oxygen saturation.2Respiratory Medicine. Platypnea-orthodeoxia syndrome: A review
What makes the condition positional is that the shunt opens or worsens specifically when the body is upright. When you stand or sit, gravity shifts the heart’s position slightly, and changes in blood flow and pressure across the shunt can increase the amount of blood crossing from right to left. Lie back down, and the geometry resets; the shunt closes or shrinks, oxygen levels climb, and the breathlessness fades. That positional dependence is the hallmark that separates platypnea from other causes of low oxygen.3PubMed Central. Platypnea-Orthodeoxia Syndrome Due to Patent Foramen Ovale: A Diagnostic and Therapeutic Challenge
The Most Common Culprit: A Hole in the Heart
A review of published cases found that a patent foramen ovale (PFO) is the most frequently reported source of the shunt in platypnea-orthodeoxia syndrome.4Respiratory Medicine. Platypnea-orthodeoxia syndrome: A review A PFO is a small flap-like opening between the heart’s two upper chambers. Everyone has this opening before birth because fetal circulation bypasses the lungs; it normally seals shut in infancy. In roughly a quarter of adults, though, it never closes completely. Most of those people never know about it, because the pressure on the left side of the heart typically keeps the flap pressed shut.
POS develops when something redirects blood flow so that the flap is pushed open. In the upright position, the anatomy of the chest shifts just enough to funnel blood toward the opening, and oxygen-poor blood streams from the right atrium into the left. Other intracardiac openings can do the same thing, including atrial septal defects (actual holes rather than flaps) and atrial septal aneurysms, where the tissue between the chambers bulges and allows intermittent crossing.5Respiratory Medicine. Platypnea-orthodeoxia syndrome: A review
Why Symptoms Often Appear Late in Life
If a PFO has been present since birth, you might wonder why someone would develop platypnea-orthodeoxia syndrome at 70 rather than at 20. The answer usually lies in acquired changes to the chest’s anatomy that accumulate with age. As the aorta elongates and becomes more tortuous over decades, it can push against the atrial septum and physically redirect blood flow toward the PFO. A shortened distance between the aortic root and the back wall of the atrium has the same effect, essentially warping the septum so the flap is more easily lifted open.6PubMed Central. Platypnea-Orthodeoxia Syndrome in the Setting of Patent Foramen Ovale Without Pulmonary Hypertension or Major Lung Disease
A case series examining adults with platypnea-orthodeoxia syndrome found that acquired anatomical changes, specifically age-related tortuosity and elongation of the aorta, could favor right-to-left shunting through congenital openings that had been hemodynamically silent for decades.7PubMed Central. Anatomical factors triggering platypnea-orthodeoxia in adults This explains why most diagnosed patients are older adults and why a PFO that caused no trouble at age 40 can become clinically significant after structural shifts in the chest.
Other anatomical variants can act as the trigger rather than the aorta. In one reported case, a prominent eustachian valve, a ridge of tissue near the opening of the inferior vena cava, extended far enough to direct incoming venous blood straight toward the interatrial septum and across a defect.8PubMed Central. Platypnea Orthodeoxia Syndrome Secondary to a Persistent Eustachian Valve These anatomical details underline an important point: the syndrome almost always requires two ingredients, a potential shunt and something that steers blood flow through it.
Causes Beyond the Heart
Not every case of platypnea-orthodeoxia syndrome traces back to a hole between the heart’s chambers. The shunt can also sit in the lungs.
Hepatopulmonary syndrome (HPS) is a condition seen in people with advanced liver disease in which the tiny blood vessels in the lungs dilate abnormally. Those dilated vessels allow blood to pass through the lungs too quickly to pick up adequate oxygen, creating an effective shunt. Platypnea and orthodeoxia are recognized features of this syndrome, and the positional component is thought to involve gravity pulling blood preferentially through the dilated vessels in the lung bases when the patient sits up. Liver transplantation remains the only established cure. After transplant, roughly 80 percent of patients in one series showed complete resolution, though the mortality rate was higher in those with severe disease.9PubMed Central. Hepatopulmonary Syndrome and Liver Transplantation: A Recent Review of the Literature In rare instances, platypnea and orthodeoxia persisted even after transplant, requiring additional treatment with embolization of the abnormal vessels.10Hepatology. Failure of hepatopulmonary syndrome to resolve after liver transplantation and successful treatment with embolotherapy
Pulmonary arteriovenous malformations (PAVMs) are another source. These are direct connections between pulmonary arteries and veins that bypass the gas-exchange capillaries entirely. PAVMs can be isolated findings, but they are commonly associated with hereditary hemorrhagic telangiectasia, a genetic condition that affects blood-vessel formation throughout the body. Platypnea-orthodeoxia syndrome has been reported as a presenting feature of that disorder.11PubMed Central. Platypnea-orthodeoxia syndrome as a presentation of hereditary hemorrhagic telangiectasia
When Diaphragm Problems Join the Picture
The diaphragm’s role in platypnea-orthodeoxia syndrome is a less intuitive connection. In a documented case, a patient with a paralyzed right hemidiaphragm developed positional breathlessness and falling oxygen levels when upright. Investigation revealed a PFO, and the explanation tied the two together: the paralyzed diaphragm rose higher in the chest, compressing the right lung and altering the pressure dynamics enough to push blood across the PFO. Percutaneous closure of the PFO resolved the symptoms.12PubMed Central. Platypnoea-orthodeoxia syndrome and hemidiaphragm paralysis This pattern reinforces the two-ingredient model: a potential shunt (the PFO) needs a functional trigger (the displaced diaphragm changing pressure relationships) before the syndrome manifests.
COVID-19 and Platypnea-Orthodeoxia Syndrome
The pandemic brought platypnea-orthodeoxia syndrome to the attention of a wider medical audience. In a cohort of 20 patients recovering from severe COVID-19 pneumonia, five developed the syndrome after coming off mechanical ventilation. The oxygen-saturation drops on sitting upright were substantial, with a median desaturation of 8 percent. The affected patients tended to be older and leaner than those without POS. The good news was that the condition resolved on its own over a median of 17 days as the underlying lung disease improved.13PubMed Central. Reversible platypnea-orthodeoxia in COVID-19 acute respiratory distress syndrome survivors
Clinically, POS in COVID-19 survivors surfaced most visibly during physical rehabilitation sessions, when patients were helped into an upright position and their oxygen levels dropped noticeably. This hindered early mobilization and delayed the transition to walking.14PubMed Central. Rehabilitation of Patients with Platypnea-Orthodeoxia Syndrome in COVID-19 Pneumonia: Two Case Reports The mechanism in these cases was likely different from the classic PFO-driven syndrome. Extensive lung damage from the virus probably created regions of intrapulmonary shunting that worsened with positional changes in blood flow. Recognizing the syndrome spared patients from unnecessary invasive cardiac workups and allowed clinicians to simply adjust rehabilitation timelines.
How the Syndrome Is Diagnosed
Because platypnea is the opposite of the more familiar orthopnea, it can slip past clinicians who are not specifically looking for a positional pattern. The first clue is usually a discrepancy in oxygen saturation readings: fine when lying in a hospital bed, worrisomely low when sitting in a chair or walking. A deliberate positional assessment, measuring oxygen levels in both supine and upright positions, is the simplest screening step.
When the positional drop is confirmed, the diagnostic workup typically centers on finding the shunt. Contrast echocardiography, in which agitated saline is injected into a vein and tracked on ultrasound as it passes through the heart, is one of the most revealing tests. In a normal heart, the microbubbles stay on the right side. If they appear on the left side within a few heartbeats, a cardiac shunt is present. Performing this test on a tilt table, with the patient shifted between supine and upright positions, can demonstrate that the shunt opens or increases in the upright position, directly confirming the positional mechanism.15PubMed Central. Diagnostic Utility of a Transcatheter Bubble Test for Platypnea-Orthodeoxia Syndrome in Adult Congenital Heart Disease With Chronic Obstructive Pulmonary Disease
Further imaging may include transesophageal echocardiography for a closer look at the atrial septum, or CT angiography of the lungs if pulmonary arteriovenous malformations are suspected. In patients with liver disease, the diagnostic path shifts toward evaluating hepatopulmonary syndrome.
Treatment and Outcomes
When the shunt is an intracardiac opening like a PFO or ASD, percutaneous closure is the standard treatment. A catheter-delivered device is threaded through a vein and positioned across the defect to seal it. The results can be dramatic. In a series of patients treated at one center, oxygen saturation jumped from an average of about 81 percent before the procedure to about 95 percent on room air immediately afterward, and none of the patients required re-intervention.16PubMed. Percutaneous Intervention to Treat Platypnea-Orthodeoxia Syndrome: The Toronto Experience That kind of immediate improvement is striking and tends to be durable, because once the hole is sealed, the positional blood-flow redirection no longer has anywhere to go.
The approach differs when the shunt is outside the heart. For hepatopulmonary syndrome, as noted earlier, liver transplantation is the definitive treatment. For pulmonary arteriovenous malformations, catheter-based embolization can plug the abnormal connections, though in hereditary hemorrhagic telangiectasia new malformations may develop over time and require surveillance. When the POS is secondary to a reversible condition like COVID-19 lung damage, supportive care and time are often sufficient.
Children and Platypnea-Orthodeoxia Syndrome
The syndrome overwhelmingly affects adults, which makes pediatric cases notable. One published report described a 12-year-old girl who developed positional breathlessness and desaturation traced to a PFO. Percutaneous closure resolved her symptoms, just as it does in older patients.17PubMed. Platypnea-orthodeoxia syndrome in a child: relief of symptoms after transcatheter closure of patent foramen ovale Cases like this are rare partly because the age-related anatomical changes that typically redirect blood flow toward a PFO have not yet occurred in children. When POS does appear in a young person, it suggests that the anatomy of the defect itself, or some other structural quirk, is severe enough to create the shunt without the help of decades of aortic remodeling.
Other Forms of Positional Breathlessness
Platypnea is one of several recognized patterns of positional dyspnea, and telling them apart matters because each pattern points to a different set of causes. Orthopnea, the most common type, is breathlessness that worsens when lying flat and is the classic sign of heart failure. Trepopnea refers to breathlessness that depends on which side you lie on, often seen with large pleural effusions or certain types of heart disease. Bendopnea is breathlessness triggered by bending forward, as when tying shoes, and is associated with advanced heart failure where the bending position raises cardiac filling pressures.18PubMed. Positional dyspnea: A brief review
What sets platypnea apart is that the patient feels worst in the very position most people breathe most easily: upright. This counterintuitiveness is probably why it goes unrecognized. A patient who reports difficulty breathing when sitting up may be assumed to have deconditioning or anxiety rather than a shunt that opens with postural change. Clinicians who have never encountered the syndrome may not think to check oxygen saturation in two positions, and the diagnosis slips through.
How the Syndrome Got Its Name
The condition was first described in 1949, and by the mid-twentieth century a handful of case reports had established both the clinical pattern and its responsiveness to closure of a cardiac defect.19Mayo Clinic Proceedings. Platypnea-Orthodeoxia: Clinical Profile, Diagnostic Workup, Management, and Report of Seven Cases The name “platypnea” draws from Greek roots meaning “flat” and “breathing,” reflecting the observation that breathing is better when the patient is flat. “Orthodeoxia” pairs “upright” with “deoxygenation,” capturing the measurable oxygen drop in the standing position. Despite having been recognized for over 70 years, the syndrome remains classified as uncommon, and the published literature is dominated by case reports and small series rather than large trials.20PubMed Central. Platypnea-Orthodeoxia Syndrome: Two Case Reports That scarcity means no standardized diagnostic or management guidelines exist, and clinical decisions rely heavily on the individual workup for each patient.
Awareness and Misdiagnosis
Perhaps the biggest practical barrier with platypnea-orthodeoxia syndrome is that many clinicians have never heard of it. Because the condition is rare and paradoxical, patients can cycle through extensive pulmonary workups, receive misdiagnoses of COPD exacerbation or interstitial lung disease, and undergo treatments that never address the actual shunt. High clinical suspicion is essential: any patient whose oxygen levels consistently fall when upright and recover when supine should prompt a positional assessment and, if confirmed, an evaluation for intracardiac or intrapulmonary shunting.21PubMed Central. Platypnea-Orthodeoxia Syndrome: Diagnostic Challenge and the Importance of Heightened Clinical Suspicion When the diagnosis is made and the shunt is accessible, the fix can be remarkably effective, turning a patient who desaturates every time they sit in a chair into someone breathing comfortably on room air within hours of a catheter procedure.