Overview of Cardiopulmonary Exercise Testing
Cardiopulmonary exercise testing, or CPET, is a type of test that isn’t used as often as it could be but it provides lots of important information about a patient’s physical health. This test provides a live look at how the heart and lungs are functioning, catching any underlying heart or lung disease that may be missed by standard tests like electrocardiograms (EKGs), echocardiography (an ultrasound of the heart), or spirometry (breathing tests).
This type of test can be especially useful if a patient seems to be more tired, out of breath, or struggling with physical activity more than these standard tests are showing. During CPET, doctors will monitor a patient’s EKG, heart rate, and the levels of oxygen they’re using and carbon dioxide they’re producing while they exercise. This information can be used to figure out how much air the patient is breathing in a minute (minute ventilation) and the maximum amount of oxygen that the patient can use (VO2 max).
By looking at all these factors, doctors can assess the overall function of the heart and lungs, and this could be used in different situations. For instance, it helps in determining surgical risks before an operation (pre-operative risk assessment), diagnosing various heart and lung diseases, assessing recovery after surgery (post-operative recovery), or simply understanding a person’s overall ability to exercise.
Anatomy and Physiology of Cardiopulmonary Exercise Testing
When doctors talk about CPET, they’re referring to a test that looks at the heart and lungs and how they work together. Think of your heart and lungs as a tightly knit team – they depend on each other to function efficiently. Breaking them down further, each lung and heart is composed of smaller parts (lung segments and heart chambers), but these parts still work closely together.
Here’s how it works in simpler terms: Deoxygenated blood, or blood that’s used up its oxygen supply, returns to your heart from all parts of your body. This blood reaches the right side of your heart and gets pushed into your lungs, where it gets refreshed with fresh oxygen. This oxygen replacement happens in tiny structures called alveoli, which is also where waste like carbon dioxide gets expelled. Now full of oxygen, the blood returns to the heart and is then pumped back out to the rest of the body again.
This system also helps supply the heart and lungs with the blood they need to function. By doing the CPET, doctors can evaluate how well this system is working both at rest and during times when it’s being pushed harder, like during exercise. It’s a great example of how the structure of our bodies directly affects how they function.
Why do People Need Cardiopulmonary Exercise Testing
Cardiopulmonary exercise testing (CPET) is a valuable tool in diagnosing a variety of conditions due to its ability to provide detailed information about how different systems in your body are functioning. Generally, we use this test for five main reasons:
1. Figuring out what’s causing exercise difficulties.
2. Evaluating functional abilities, which refers to how well you can perform various physical tasks.
3. Identifying risk levels for surgeries.
4. Helping to predict how specific diseases might develop or change.
5. Crafting custom workout plans for rehabilitation programs.
For those suffering from heart failure, whether their heart is pumping normally or not, this test can be beneficial. It can help identify if you’re having trouble exercising, a common issue with heart disease. Importantly, CPET was used for categorizing heart failure patients based on their peak oxygen usage during exercise, a significant development in cardiology.
Another significant usage is using peak oxygen usage during intense exercise to identify the cardiovascular risk that heart failure patients might face within a year. Several cardiology labs have confirmed these findings, creating algorithms to help manage heart failure patients in all stages effectively. Doctors also use this test when evaluating possible heart disease, birth defects in the heart, heart valve diseases, an enlarged heart (hypertrophic cardiomyopathy), or high blood pressure in the lungs (pulmonary hypertension).
Furthermore, CPET is also used to assess the risk level of patients before they undergo surgery, including operations for issues within and outside the chest area. For instance, the American College of Chest Physicians uses CPET data to rate the condition of lung cancer patients before surgery.
When a Person Should Avoid Cardiopulmonary Exercise Testing
Cardiopulmonary exercise testing (CPET) is a safe procedure for most people. However, there are some situations where it might not be the safest option. Here are some absolute and relative contraindications for CPET.
Absolute contraindications are reasons why you definitely should not undergo CPET:
* Active heart muscle damage
* Unmanaged heart failure
* Fainting after exercise
* Uncontrolled or untreated irregular heart rhythms
* Severe tightness in your aorta, the main artery carrying blood from your heart
* Inflammation of your heart or its lining
* A tear in your aorta, or a possibly cracking aortic aneurysm, which is a bulge in the wall of your aorta
* Untreated blood clots in your lungs or deep veins
* Flare-up or uncontrolled chronic lung disease (COPD) or asthma
* Fluid in your lungs
* Oxygen levels below 85% when not doing anything
* Severe difficulty breathing
Here are some relative contraindications – these only apply if you’re not in a stable enough state for CPET:
* Severely high pressure in the blood vessels supplying your lungs
* Untreated blockage of the main artery supplying blood to your heart
* Medium-level tightness affecting your heart valves
* Very high blood pressure (above 200/120)
* Abnormally thick heart muscle
* Second or third-degree block of the electrical system of your heart
* Unfixed electrolyte imbalances, which may affect how your cells work
* Fast or slow heartbeat symptoms
* Advanced or complicated pregnancy
* Can’t check or temporarily turn off a cardiac defibrillator because the device specialist isn’t available
Equipment used for Cardiopulmonary Exercise Testing
There are many different types of exercise monitoring systems that people can buy. These machines can measure the gases you breathe out with each breath. They also can analyze the amount of oxygen and carbon dioxide you breathe in and out in real time.
These systems can even measure the amount of air you breathe in and out by using a device called an airflow transducer. Usually, these exercises are done using a stationary bike or a motorized treadmill. It’s very important that these exercises can be repeated in the same way each time and that they are safe for the person doing them.
Both of these exercise machines can provide increased resistance, helping to measure a person’s effort over time, usually measured in watts. However, it’s been found that the maximum amount of oxygen people can use during exercise is 5% to 20% greater when they’re on a treadmill versus a stationary bike, because more muscle groups are involved in the exercise.
Among the other equipment used in these systems is a metabolic cart which includes a gas analyzer, a computer, and a screen that displays both the electrical activity of the heart (EKG analysis) as well as physiological changes as they happen during exercise.
Who is needed to perform Cardiopulmonary Exercise Testing?
Cardiopulmonary Exercise Test (CPET) is a test that collects a lot of data, so it’s considered a specialty test conducted in dedicated heart or lung testing centers. Medical technicians with expertise in heart stress testing and lung function tests are the individuals conducting the CPET. If you live in a place with lots of healthcare resources, you may find centers that offer a complete care package. This might include a check-up with a health expert, a basic heart tracing or EKG, an echocardiogram (heart ultrasound), the CPET itself, and discussions on exercise, healthy eating, and effective management of your health conditions.
Preparing for Cardiopulmonary Exercise Testing
Cardiopulmonary exercise testing, also known as CPET, is typically done at specialized healthcare centers that also perform other tests related to the heart and lungs. Before the test, the healthcare team will explain to the patient about the equipment that will be used and what type of data will be collected. If a patient has a high risk of falling, doctors will use certain equipment, like a cycle ergometer (like a stationary bicycle), to reduce this risk during the test.
How is Cardiopulmonary Exercise Testing performed
To test the maximum amount of oxygen a non-athlete person can use during intense exercise, a machine called a cycle ergometer is used. This test is done in a room with good air flow, and with equipment on hand in case of medical emergencies.
The cycle ergometer is connected to a computer which keeps track of heart activity (EKG data) and how your body is reacting to the exercise. This is done by monitoring things like how much oxygen you’re using and how much carbon dioxide you’re producing with each breath you take. The machine checks how quickly air is flowing in and out of your lungs before each breath, to make sure everything is properly calibrated.
Before the test starts, you get a chance to familiarize yourself with the equipment. They’ll also measure your resting heart rate, blood pressure, oxygen saturation (how much oxygen your blood is carrying), EKG, and gas exchange values (how much carbon dioxide you’re producing compared to how much oxygen you’re using).
When the test starts, you’ll be asked to pedal at a constant speed. As the test goes on, you’ll be asked to work harder and harder, which increases the amount of oxygen you use. There are different ways for the person conducting the test to gradually make the exercise more intense. Balke and Naughton put together some recommendations on how to do this.
Possible Complications of Cardiopulmonary Exercise Testing
The cardio-pulmonary exercise test (CPET) could, in some cases, lead to side effects like feeling tired and having trouble breathing. These side effects are usually tied to how physically fit a person is. Less common side effects can include irregular heartbeats, chest pain that feels like angina (which is a heart condition that causes discomfort or pain in your chest), and bronchospasm (which is when your airways suddenly constrict making it hard for you to breathe).
A doctor often supervises these tests in a hospital setting because people with health issues, like heart failure, could experience more of these side effects. So, it is typically safer to do these tests where immediate medical help is readily available if needed.
What Else Should I Know About Cardiopulmonary Exercise Testing?
Cardiopulmonary exercise testing (CPET) is a medical test that gathers information about how well your heart, lungs, and muscles are working. This test can help determine if you have a specific illness or health condition. Though the reasons to perform this test can be based on symptoms that are hard to measure, like feeling short of breath, the information it provides is precise and accurate, making it extremely useful to healthcare providers.
A key part of analyzing the results from a CPET is to find out if a patient reaches what’s called the ventilatory threshold during the test. This threshold is the point during exercise where your body can’t get enough oxygen to your active muscles to meet the demands they’re making. Sometimes, it’s also called the lactate or anaerobic threshold, and it typically kicks in at 50% to 60% of your maximum oxygen use.
While scientists don’t fully understand all the details yet, reaching this threshold increases the production of lactic acid in your muscles. This, in turn, causes an increase in hydrogen ions in your body, which boosts your carbon dioxide production. This chemical reaction helps balance the pH inside your cells, which can get disturbed during intense exercise.
Identifying if and when a patient reaches this ventilatory threshold can reveal important information about why a person might struggle with exercise. The response could indicate an issue with the heart and lungs or a problem with breathing function. Knowing when this threshold is reached can also be used as a starting point for developing an exercise rehabilitation program aimed at aiding recovery or improving overall fitness.
