|Cardiopulmonary Exercise Test|
The Cardiopulmonary Exercise Test is a highly sensitive, non-invasive stress test. It is considered a stress test because the exercise stresses your body’s systems by making them work faster and harder. A disease or condition that affects the heart, lungs or muscles will limit how much faster and harder these systems can work. A CPET assesses how well the heart, lungs, and muscles are working individually, and how these systems are working in unison. Your heart and lungs work together to deliver oxygen to your muscles, where it is used to make energy, and to remove carbon dioxide from your body.
The full cardiopulmonary system is assessed during a CPET by measuring the amount of oxygen your body is using, the amount of carbon dioxide it is producing, your breathing pattern, and electrocardiogram (EKG) while you are riding a stationary bicycle.
The traditional treadmill stress test only relies on the EKG, which only partially assesses the heart and nothing else. Besides detecting problems in multiple body systems, the CPET is also used to monitor changes in your disease condition, the effect of certain medications on your body, and if medical therapy is improving your condition.
Heart, lung, and metabolic conditions may cause shortness of breath, exercise intolerance or discomfort and pain in the chest. The CPET is the only test that can simultaneously determine which of these systems is causing the problem. Not only can the CPET determine if the problem is in the heart, lungs or muscles, but it can specifically detect the following conditions:
1. Heart Failure – The inability of the heart to pump enough blood to meet the needs of the body’s other organs (ex: CHF, diastolic heart failure, systolic heart failure).
2. Myocardial Ischemia (Heart disease) – Reduced blood flow to one or more parts of the heart due to blockage or spasm (ex: CAD). Blockage of either the large blood vessels (macrovascular) or small blood vessels (microvascular) can be detected by CPET.
3. Cardiac valve dysfunction – Valves do not open and close properly to contain blood inside the chambers of the heart (ex: mitral valve prolapse, stenosis).
4. Chronotropic incompetence – Inability of the heart to increase speed of contraction (heart rate) due to medication or intrinsic factors.
5. Pulmonary ventilation disorder – Lungs are not able to take in enough air to meet the body’s demands (ex: asthma, COPD, emphysema).
6. Pulmonary circulation disorder – Inability of the body to pull oxygen from the lungs into the bloodstream (ex: blood clot in lungs, pulmonary vascular disease, scarring in the lungs, heart failure).
7. Muscle metabolic disorders – Inability of the muscle cells to use oxygen from the bloodstream to produce energy for the working muscle tissues (ex: mitochondria disorders, McArdle’s disease, enzyme deficiency).
8. Deconditioning – Poor cardiovascular fitness that can be improved with exercise.
The CPET is also used to monitor patients who already have known medical conditions and to determine how a patient is responding to medical treatments. In comparison, traditional treadmill stress tests are generally only used for detection of ischemia (heart disease - macrovascular). The CPET is significantly more accurate in detecting ischemia and can identify many more conditions.
Unlike a traditional stress test, the CPET is performed on a stationary bicycle, which is safer than a treadmill. Many patients also feel more comfortable riding the bicycle than walking on a treadmill. During the test various pieces of equipment will be used to monitor your body’s response. This equipment includes:
Face mask: This monitors the oxygen used, carbon dioxide produced, and the breathing pattern. The mask is placed over the mouth and nose (similar to an airplane pilot’s mask). It does not restrict breathing and you will only be breathing-in air from the environment.
Electrocardiogram (EKG): Ten stickers will be placed on your chest with monitoring wires attached. This is used to monitor your heart rate and rhythm.
Blood pressure cuff: Your blood pressure will be taken multiple times during the test.
Pulse oximeter: This is a small device that slides over your finger and uses a light to measure the percentage of blood cells covered with oxygen.
Before exercise begins, you will be asked to perform 2 lung tests. The results of these tests will be compared to your breathing during exercise. Your technician will then fit the required equipment to you and help you get on the bicycle. While you are resting on the bicycle, your technician will explain the testing procedure in greater detail. At the end of the rest period, you will be asked to begin pedaling lightly for a few minutes, to warm up. The resistance on the bicycle will then slowly become harder and harder as if you were going up a hill that keeps gently getting steeper and steeper. The test will continue until you are giving your maximum effort and can no longer continue.
To get the most accurate results for your doctor, it is important that you give your best effort for as long as you possibly can. If you do not give a maximum effort, your test may be “indeterminate” and your doctor will not have the most accurate information to help you. The exercise work load will be adjusted on an individual basis to help each person give his or her best effort.
Your technician will keep encouraging you to continue to get your best effort until he or she sees that you cannot continue. However, if your technician notices that you are experiencing certain symptoms the test will be immediately stopped. After the test is over, your technician will ask you to pedal slowly and gently to cool down while he or she continues monitoring your vital signs.
After you have rested for several minutes, your tech will ask you to repeat one of the lung tests to determine if exercise changes the way your lungs function.
The actual time it takes to perform the test, from the time you get on the bike, through the exercise portion and recovery will be between 15 and 25 minutes. However, you will only be asked to exercise at a hard intensity for about 3 to 4 minutes.
Additional tips for a successful test:
Give your best effort and exercise for as long and hard as possible.
Keep your legs moving at the same speed for the entire test, even when it is difficult.
Avoid speaking during the test unless you have discomfort or pain.
Let the technician know if you have discomfort or pain at any point during the test.
A CPET is quite different than other stress tests you might have had in the past. Other tests use treadmills, whereas a CPET uses a stationary bicycle. This allows a wider range of people to complete an exercise stress test that may not otherwise be able to. The bicycle allows for the exercise level to be increased a little at a time, rather than in big jumps, like during a treadmill test. This steady increase makes it easier for the body to handle. A bicycle is also safer than a treadmill because you are more stable and there are fewer chances to fall. Studies also show that patients performing an exercise test on a stationary cycle have a lower risk of cardiac events (heart attack, stroke, dangerous arrhythmias) during the test.
A Cardiopulmonary Exercise Test may take 45 to 60 minutes to complete. The rest, exercise, and recovery lasts for a total of about 15-25 minutes, but you will only be exercising at high levels for 3-4 of those minutes. The rest of the time will be spent connecting and disconnecting the equipment, completing the health history, and performing the before and after exercise pulmonary tests.
Since you will be exercising, be sure to wear comfortable clothing and proper footwear for riding a bicycle. Do not wear a dress, skirt or full slip. You will be wearing EKG leads on your chest, so you should not wear one piece outfits or clothing that prevents easy access to your chest. Closed toe shoes are required for testing. Do not wear high heals, sandals or flip flops. This type of clothing and foot wear make pedaling a bicycle quite difficult. Do not eat or drink (except water) for 3 hours before your test. Exercise or physical labor should be avoided for 24 hours before your test. Bring a list of your current medications with you to your test. Your doctor’s office will tell you if you are supposed to take your medications before the test, but if you are unsure, contact your doctor. If you have any questions about your test please contact your doctor’s office and ask to speak with the MET-TEST technician. (S)he will answer any questions you might have, or direct you to the proper person who can answer your questions.