Cardiopulmonary Exercise Test (CPET)

What is CPET?

Cardiopulmonary exercise test (CPET), also called a metabolic exercise stress test, is an assessment that checks your heart and lung function at the same time. You exercise on a bike or treadmill while breathing through a facemask or mouthpiece. The results determine how well your heart, lungs and blood vessels can send oxygen to your muscles during physical activity. This makes CPET different from a cardiac stress test, which only evaluates your heart.

CPET plays an important role in managing many heart and lung conditions. A healthcare provider may recommend this test to:

• Find out why you’re short of breath or very tired during physical activity
• Show how much exercise your heart and lungs can handle
• Diagnose or monitor a heart or lung disease, like heart failure, congenital heart disease, pulmonary hypertension or COPD
• Guide your treatment plan
• Learn what you might expect down the road (your prognosis)
• Develop an exercise plan that’s safe and effective for you
• Evaluate your risk for complications before having surgery, like a lung resection or lung transplant
• Make sure you can safely perform a physically demanding job

How does the test work?

Cardiopulmonary exercise testing takes place in a stress lab (a room where people have stress tests). A lab technician will perform the test, while a physician supervises. You’ll either cycle on a stationary bike or walk on a treadmill. You’ll exercise for as long as you can. Every minute or so, the technician will increase the resistance on the bike or treadmill so it gets harder to keep going. The test will end when you’re too tired to continue.

While you exercise, you’ll breathe into a facemask or mouthpiece. This device measures the amount of oxygen and carbon dioxide in the air you inhale and exhale. It also measures how much air your lungs can take in. If the test is performed on a bike, the resistance will increase gradually. If the test is performed on a treadmill, the speed will increase.

How do I prepare?

Your healthcare provider will explain how you should prepare for CPET.

In general, you should NOT:

• Have any caffeine for 24 hours before the test
• Smoke or vape for eight hours before the test
• Eat or drink anything except water for four hours before the test

Before cardiopulmonary exercise testing, be sure to tell your provider about:

• Medicines you take: These include prescription and over-the-counter ones. They may ask you to stop taking some before your test. If you take insulin to manage your blood sugar, ask your provider what amount you should take the day of the test.
• Recent changes to your health: Let your provider know if you’ve been sick or had an injury. They may want to reschedule your test to a time that’s safer for you.
• Implanted medical devices: If you have a pacemaker or defibrillator, your provider must check it before the test. Call them to schedule a device check in advance of your test day.

Wear clothes and shoes you’re comfortable exercising in for your test.

What happens during CPET?

Cardiopulmonary exercise testing involves the following steps:

1. Preparation: Your technician will put stickers (EKG electrodes) on your chest, place a blood pressure cuff on your arm and put a pulse oximeter on your finger. They may insert a thin tube (catheter) into a wrist artery to measure arterial blood gas.
2. Rest: You’ll stay still for two to three minutes while your technician collects baseline data. They’ll make a note of things like your heart rate and rhythm, blood pressure and blood oxygen levels.
3. Warm-up: You’ll walk or cycle slowly, without resistance, for two to three minutes. Your technician gathers “active baseline” information to see how your heart and lungs respond to very light exercise.
4. Incremental exercise: This usually lasts eight to 12 minutes. You’ll steadily walk or cycle as your technician gradually adds resistance or increases the pace (depending on the mode of testing). It’ll feel harder to continue. Keep going as long as you can.
5. Cool-down: This lasts three to five minutes. You walk or cycle with no resistance, as you did during the warm-up.

Throughout the test, your technician will keep a close eye on your vital signs and make sure you’re OK. They may ask you to use hand gestures to share how you’re feeling. For example, you might rate how hard you feel you’re pushing yourself on a scale of 1 to 10 (this is called a rate of perceived exertion (RPE) scale).

Your appointment will take about 75 minutes. You’ll be exercising for up to 20 minutes, including the warm-up and cool-down.

How will I feel during the test?

To get the most accurate and helpful test results, you should exercise until you’re exhausted. It’s normal for your heart rate, blood pressure and breathing rate to go up. You’ll also feel sweaty, and your legs will feel more and more tired. Your mouth may feel dry from breathing through the mouthpiece.

CPET is a workout, and it’ll feel like one. But if you have unusual symptoms during the test, stop exercising and tell your technician immediately. These symptoms include:

• Pain, discomfort or tightness in your chest, arm or jaw
• Extreme shortness of breath
• Dizziness or feeling like you’re going to pass out

These symptoms could signal a heart attack or other medical emergency. Lab technicians will watch for any worrisome changes on the EKG monitor. They’ll stop the test immediately if needed.

What are the risks of this test?

CPET happens in a safe and controlled environment. Still, it’s hard to predict exactly how your body will respond to intense exercise. Possible risks include passing out, having a heart attack or other emergencies. But lab staff are prepared to respond and treat you on the spot.

Your healthcare provider will make sure the test is low-risk for you before you set foot in the lab. For example, they may decide the test isn’t safe for you to do if you have any of the following:

• Acute infection, including cold, flu and COVID-19
• Acute heart inflammation
• Deep vein thrombosis (DVT) in your legs
• Hypertrophic cardiomyopathy
• Kidney failure
• Moderate or severe heart valve stenosis
• Pregnancy that’s advanced or complicated
• Recent history (within 30 days) of a heart attack
• Severe hypertension (high blood pressure throughout your body) or pulmonary hypertension (high blood pressure in your lungs)
• Uncontrolled arrhythmias

What to expect after CPET?

Once you’re done cooling down, your technician will check your vitals and then remove the devices. You’ll sit down, have some water and relax a bit. Lab staff will make sure you’re feeling well. They’ll let you know when it’s safe for you to leave.

The healthcare provider who ordered the test will schedule a time to meet with you and discuss the results.

What type of results do you get?

CPET records thousands of measurements into a format known as a nine-panel plot. This is a set of complex, technical graphs that show many details about your heart and lung function. Your provider will interpret the graphs and add a summary of what they mean. They’ll also explain to you any next steps, including further testing or treatments you might need.