Do you sometimes find it hard to breathe even when you run a little, or when you climb a flight of stairs? Or do you feel incredibly tired? Your doctor may have told you about a 'stress test'. It checks how your heart works during exercise. But today we're talking about a special test that looks at the function of both your heart and lungs in a more in-depth way. This is called a CPET, or Cardiopulmonary Exercise Test.
Simply put, what is CPET?
CPET is a test that measures your heart (cardio) and lung (pulmonary) function while you exercise. It's also called a 'metabolic exercise stress test'. It's very simple. You'll be asked to walk on a treadmill or ride a stationary bike. During this time, you'll be fitted with a special facemask or mouthpiece that allows you to breathe only through your mouth.
This measures how well your heart, lungs, and blood vessels work together to deliver oxygen to your muscles when you exercise. A typical cardiac stress test only looks at your heart. But a CPET test is more valuable because it provides information about both your heart and lungs at the same time .
Why would a doctor recommend this test?
There are several reasons why your doctor might recommend this test. For example, you may have one of the following problems:
- Find out why you're short of breath or feel very tired when you exercise: Some people find that they get very tired when they're slightly tired. This test can help determine if the cause is a heart problem, a lung problem, or something else.
- See how much exercise your heart and lungs can handle: This is important to know what level of exercise is safe before starting exercise, especially for someone with heart disease.
- Diagnose or monitor heart or lung diseases: This test is used to determine the severity of conditions such as heart failure, congenital heart disease, pulmonary hypertension, or COPD.
- Develop your treatment plan: This data is useful for determining whether the medications you are taking are working properly and whether there is any improvement in your condition after treatment.
- Get an idea of the future health status (Prognosis): You can get some idea about the future of a disease, that is, whether the condition will get better or worse.
- Create a safe exercise plan that works for you: Not everyone is suited to the same type of exercise. This will help you plan what exercises are best for your body and for how long.
- Assess the risks before major surgery: For example, before undergoing a lung resection or lung transplant, it is essential to assess whether your body can tolerate the surgery.
- Make sure you can safely perform a physically demanding job: Some jobs (e.g. firefighters, military personnel) require a high level of physical fitness. This test is also used to determine if you are suitable for them.
How do you do this test?
The CPET test is performed in a special room called a 'Stress Lab'. Hospitals usually have a dedicated unit for this purpose. Although this test is performed by a trained lab technician, everything happens under the supervision of a doctor.
You will either have to ride a stationary bike or walk on a treadmill. You will have to exercise for as long as you can . Every minute or two, the technician will gradually increase the resistance of the bike, or the speed and incline of the treadmill. Then, you will start to find it harder to exercise. The test will stop when you feel like you can't do it anymore .
During this entire time, you breathe through the aforementioned mask. This device measures the amount of oxygen in the air you inhale and the amount of carbon dioxide in the air you exhale. It also measures the amount of air your lungs can take in at one time. All of this data is recorded on a computer.
How do you prepare before the test?
Your doctor will clearly tell you how to prepare for this test. It is very important to follow those instructions exactly. Below are some general things to follow. Let's look at a table to make it easier to remember these things clearly.
| Things not to do | Things to tell your doctor |
|---|---|
| Avoid anything containing caffeine for 24 hours: that is, don't drink coffee, tea, chocolate, or some soft drinks. | Medications you take: Tell your doctor about all medications you take (prescribed and over-the-counter). Some medications may require you to stop taking them the day before the test. If you take insulin for diabetes, be sure to ask your doctor about the dosage you should take on the day of the test. |
| Avoid smoking for 8 hours: Do not smoke cigarettes or vape. | Recent health changes: Tell us if you've recently had a fever, a cold, or been in an accident. You may be able to postpone the test until you're fully recovered. |
| Do not eat or drink anything other than water for 4 hours. | Implanted devices: If you have a device like a pacemaker or defibrillator, it will need to be checked before the test. So call your doctor in advance and make an appointment. |
Don't forget to wear comfortable exercise clothes and shoes when you go to the test. You can't run on a treadmill in a shirt or jeans, right?
What happens during the test?
The test is done in several stages. The entire test can take about 75 minutes. But you'll actually be exercising for about 20 minutes.
See the steps below.
1. Preparation: First, the technician will place some stickers on your chest. These are called EKG electrodes. These will monitor your heart rate. Then, a blood pressure cuff will be placed on your arm, and a pulse oximeter will be placed on your finger. Sometimes, a very thin tube (catheter) may be inserted into an artery in your wrist to measure your arterial blood gas.
2. Rest: Next, you will be asked to do nothing for two to three minutes. During this time, your normal heart rate, blood pressure, and oxygen levels will be recorded as baseline values.
3. Warm-up: Then you walk on a treadmill or ride a bike for two to three minutes at a very gentle pace, without any weights. This tests how your heart and lungs respond to very light exercise.
4. Incremental Exercise: This is the most important part of the test. It usually lasts between 8 and 12 minutes. You continue to exercise as the technician gradually increases the weight. It will gradually become more difficult for you. This is when you need to push yourself as hard as you can.
5. Cool-down: When you can't do any more, stop the main part of the test. Then, for about three to five minutes, slowly and without any weight, you exercise again. This allows the body to gradually recover.
The technician will be monitoring your condition closely throughout this time. You may also be asked to use hand signals to ask how you are feeling. For example, on a scale of 1 to 10, they may ask you to rate how tired you are.
How will you feel when you take the test?
To get accurate and beneficial results, you need to exercise until you are really tired . Therefore, it is normal for your heart rate, blood pressure, and breathing rate to increase. You may sweat and your legs may feel very tired. It is also normal for your mouth to dry out because you are breathing through the mask.
CPET is like a good workout. It feels like one. However, if you experience any unusual symptoms during the test, stop exercising immediately and tell the technician.
Pay special attention to symptoms like these:
- Pain, tightness, or discomfort in the chest, arm, or jaw.
- It's very difficult to breathe.
- Dizziness or a feeling of fainting.
These could be signs of an emergency, such as a heart attack. The lab staff will be watching your EKG, and if they see any dangerous changes, they will stop the test immediately.
Are there any risks with this test?
CPET is done in a very safe, controlled environment. So there's nothing to be afraid of. However, it's not 100% certain how your body will respond to intense exercise. There are very rare risks, such as loss of consciousness or heart attack. Even in the event of an emergency, the lab staff is trained to treat you on the spot.
Before you even step foot in the lab, your doctor will make sure that this test is safe for you. For example, if you have any of the following conditions, your doctor may decide that this test is not safe for you to have:
- An acute infection such as fever, cold, or COVID-19.
- Acute heart inflammation.
- A blood clot in the legs (Deep Vein Thrombosis - DVT).
- Hypertrophic cardiomyopathy.
- Kidney Failure.
- Moderate or severe heart valve stenosis.
- Late pregnancy or a pregnancy with complications.
- If you have had a recent (within 30 days) heart attack.
- Uncontrolled high blood pressure (Severe Hypertension) or high blood pressure in the lungs (Pulmonary Hypertension).
- Uncontrolled heart rhythm disorders (Uncontrolled Arrhythmias).
What happens after the test?
Once your cool-down phase is over, the technician will check your vitals again and remove any equipment you may have attached to your body. After that, you can sit down, drink some water, and rest for a while. Once they are sure you are okay, they will let you go home.
The doctor who ordered this test will set up a separate time to talk to you about the results .
What is in the report you receive?
The CPET test collects thousands of measurements. These are presented in a report with many complex graphs called 'nine-panel plots'. These are very technical and difficult for the average person to understand.
But don't worry. Your doctor will analyze all these charts and explain to you in simple terms what they mean. He will also tell you what to do next, whether more tests are needed, or whether any treatment should be started.
A CPET scan can tell you a lot about how your heart and lungs are working. It can be a bit overwhelming to have to wear all the different devices and do the exercises. But remember, each device provides vital information that can help you plan the best treatment for you.
If you have any questions before the test or want more information on how to prepare, don't hesitate to ask your doctor.
Take-Home Message
- CPET is a special test that simultaneously checks the function of your heart and lungs while you exercise.
- It is very important to follow the instructions given before the test (such as not consuming caffeine, avoiding smoking) exactly.
- You should try your best during the test, but report any warning signs, such as chest pain, immediately.
- This is a very safe, medically supervised test, so don't be unnecessarily afraid.
- Always discuss the test results and next steps with your doctor.
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