What Is Pulsus Paradoxus?

Medically Reviewed by Jabeen Begum, MD on November 17, 2021
4 min read

Pulsus paradoxus is an exaggerated drop in blood pressure when you breathe in. It isn’t a disease. Instead, it’s a symptom of an underlying condition.

Your heart and lungs work together to take in oxygen and carry it to your organs and tissues via your blood. When your heart pumps blood, the blood pushes against your artery walls. This is called blood pressure, which has two measures:

Systolic pressure: the pressure when blood pumps out of your heart

Diastolic pressure: the pressure between beats when your heart fills back up with blood

Your blood pressure naturally drops when you quietly breathe in. When you take a breath, your lungs expand and pull on the arteries to your heart, temporarily limiting the blood flow in your chest. This leads to a drop in blood flow to your heart and less blood output and, therefore, a slight drop in blood pressure. This is normal and you usually don’t notice it.

Pulsus paradoxus is an exaggerated drop in blood pressure of more than 10 millimeters of mercury, or 10 mmHg, with every breath. 

Lung and heart conditions can cause pulsus paradoxus.

Acute a sthma may lead to pulsus paradoxus. During an asthma attack, the sides of your lungs swell and cause your airways to narrow. When you have trouble getting air into your lungs, they respond by overinflating. This overinflation puts pressure on your arteries and can cause pulsus paradoxus. 

This can also happen with other lung conditions, like:

Chronic obstructive pulmonary disease. This long-term disease causes ongoing inflammation in the lungs, which leads to blocked airflow and trouble breathing. 

Situations like having a cold or being around dust and fumes can cause a COPD flare-up and worsened symptoms. This is called a COPD exacerbation and it can cause pulsus paradoxus.

Tension pneumothorax. This condition happens when your lungs are injured and air builds up in the pleura, or the lining between your lungs and chest wall. This extra air puts pressure on your lungs, which can also put pressure on the arteries to your heart and cause a drop in blood pressure.

Pleural effusion. You normally have a small amount of fluid in your pleura, which helps lubricate the outside of your lungs as they expand. Pleural effusion happens when there is too much fluid in this space. This can put pressure on your lungs and cause pulsus paradoxus.

Pulmonary embolismThis condition is caused by a blood clot traveling to an artery in your lung from somewhere else in your body. The clot blocks blood flow to your heart, which causes your blood pressure to drop. 

Some heart conditions can also cause pulsus paradoxus, such as:

Cardiac tamponade. This condition happens when fluids build up in the sac around your heart called the pericardium, compressing your heart. This causes your blood flow to drop, leading to a fall in blood pressure. Pulsus paradoxus caused by cardiac tamponade is often a medical emergency. 

Constrictive pericarditis. Sometimes the sac around your heart scars, thickens, and becomes fused to the lining of your chest wall. Your heart needs space between these linings to expand as it pumps blood. When they fuse, your heart is limited and can’t fill with blood as effectively. This leads to a drop in blood pressure followed by a sudden increase.

Taking your blood pressure is part of a routine exam, and it’s also the easiest way to measure for pulsus paradoxus. Your doctor will place a blood pressure cuff on your arm, inflate it, and listen to the differences in your pulse sounds as it starts to deflate. 

If the disease is severe, your doctor might be able to feel the differences in pressure in your pulse on your wrist.  

They might also do a pulse oximetry waveform analysis test. This is a simple test where a clip is attached to your finger to measure your oxygen saturation levels, or how much oxygen is in your blood. Your doctor will check your blood pressure and match the sounds to any changing oxygen levels.

If you have an artery catheter, your doctor can use a special machine to measure your blood pressure. 

If your doctor notices something irregular in these test results, they might order further tests like X-ray scans or an echocardiogram to check the blood flow through your heart. 

Pulsus paradoxus is a sign of an underlying condition. It’s most common in people with acute asthma, COPD exacerbation, and cardiac tamponade. Your doctor will know how to assess pulsus paradoxus and treat the underlying cause.