Pulmonary function tests are performed to identify the cause of PH. These are non-invasive tests that measure how well the lungs work. 

These tests measure: 

• how much air your lungs can hold 
• how much air moves in and out of the lungs  
• the lungs’ ability to exchange oxygen 

PFTs help health care providers check for chronic lung diseases that cause Group 3 PH. They include diseases that make it harder for air to flow out of the lungs and those that prevent the lungs from easily expanding and taking in air. 

A CT chest scan is a non-invasive test that uses radiation to create many precise pictures of the structures in the chest, including the heart and lungs. A dye is sometimes injected into the arm (i.e., a contrast) to make the images clearer. 

The test allows health care providers to see the lungs in far greater detail than with chest x-rays. Doctors can see the size of the lungs, larger blood vessels in the lungs and lung tissue. The test looks for evidence of chronic lung diseases (Group 3 PH). 

A pulmonary angiogram provides images of blood vessels in the lungs after a dye is injected to make them appear more clearly. Health care providers use the test to look at the structure and branching of the blood vessels of the lungs to find evidence of chronic blood clots (Group 4 PH). 

A V/Q scan helps doctors rule out whether you have undissolved clots in the blood vessels of your lungs. It is the gold standard screening test for Group 4 PH (CTEPH). The test compares two lung scans that show ventilation (air flow) and perfusion (blood flow). Both scans use nuclear imaging to take pictures of your lungs. 

During the ventilation scan, patients use masks to breathe in a detectable gas mixed with oxygen. The scanners take pictures as the patient breathes so the health care provider can see the sections of the lungs that receive air. 

During the perfusion scan, a traceable substance is injected into a vein in the arm. The scanner looks at which sections of the lungs receive blood flow. If there is a blockage in a pulmonary artery because of a blood clot, that section won’t appear dark on the image, but the ventilation scan could still look normal. Doctors then will decide whether to perform more tests to identify chronic blood clots in that section of the lungs and determine whether they could be removed with PTE surgery. 

Doctors might use an ultrasound of the legs to check for blood clots that contribute to Group 4 PH (CTEPH). 

Overnight oximetry is a test that measures oxygen levels in the blood. A plastic clip with a sensor is placed over the fingertip and worn overnight to measure how much oxygen is in the blood. This non-invasive test can take place at home. If oxygen levels drop below a certain point (generally 89%, set by insurance companies), for a specific length of time, oxygen therapy is recommended. 

Polysomnography is a recording of brain waves during sleep. Doctors use it to determine what causes low oxygen levels. They look at how often and how long breathing stops during sleep. They also screen for restless leg syndrome. 

The test generally takes place overnight at a sleep center.

During a blood test, a small amount of blood is drawn to assess general health and to check for specific markers for PAH–associated conditions.  These tests:

• Measure the oxygen levels in the blood 
• Observe liver, kidney and thyroid function 
• Identify whether the patient has collagen vascular disease, thyroid problems, signs of infection or HIV antibodies  

One test, the brain natriuretic peptide, helps to assess the strain on the heart and may also be used to monitor response to treatment. Doctors sometimes examine arterial blood gas (ABG) to measure arterial oxygen and carbon dioxide levels. 

If health care providers suspect a patient has liver disease, they will order an ultrasound of organs in the abdomen, including the liver, kidneys, gallbladder, spleen and pancreas. Health care providers likely will focus on the liver to check for any evidence of liver disease, which can lead to a type of PH called portopulmonary hypertension (PoPH). 

PoPH occurs as a result of advanced liver disease. It has the same characteristic symptoms as those found in cases of Group 1 PAH not associated with liver disease. 

During the right heart cath, doctors sometimes want to see how the heart and pulmonary pressures change after certain short-acting drugs. The drugs, administered by IV or inhaled, cause the pulmonary arteries to relax. 

With the catheter in the pulmonary artery, a doctor will inject the drug or give the patient a gas called nitric oxide. The doctor will take several pressure measurements within a few minutes. Doctors look for significant drops in pulmonary artery pressures, known as a positive vasodilator response. They check whether patients would benefit from drugs called calcium channel blockers (CCB). Most patients don’t have positive vasodilator responses so they receive PAH-specific therapies. 

During a Six-Minute Walk test, a patient will be asked to walk for six minutes to identify the patient’s exercise tolerance level. This test measures how far a patient can walk in six minutes. It also measures perceived exertion, heart rate and oxygen saturation (how much oxygen is in the blood). Doctors compare test results from each clinic visit as one way to measure whether PH is improving or worsening. 

Health care providers use a CPET to measure blood pressure and oxygen consumption when patients exercise (often on a stationary bike). The test identifies how well both heart and lungs respond to exercise.