Overview of Cardiopulmonary Fitness
Cardiopulmonary exercise testing (CPET) is a safe, non-invasive method of checking how well your heart, lungs, and muscles are working. The test is quite special as it can highlight problems that might not be visible when you are at rest, and can provide details about what might be causing your symptoms, such as a heart condition, lung disease, or a muscle disorder. These are determined by monitoring changes in oxygen levels, carbon dioxide levels, your breathing pattern, and heart rate during the test.[1] Its ability to provide more details than regular stress tests makes it a valuable tool for doctors, allowing them to make better treatment decisions for patients with heart, lung, and metabolic diseases.
Physical exercise performance relies heavily on how well your cardiovascular system can deliver oxygen to your body tissues and get rid of waste products from metabolism. The exchange of oxygen (O2) and carbon dioxide (CO2) in your body involves a series of steps:
1. External Respiration: This involves breathing in and out. As you breathe in, oxygen enters your bloodstream and carbon dioxide, a waste product from exercising, gets expelled as you breathe out.
2. Circulation: This is the process where your blood carries oxygen and carbon dioxide around your body.
3. Internal Respiration: At this stage, your cells make use of the oxygen, producing a chemical known as ATP which helps generate energy in the body.
When it comes to exercise, making sure your airflow (Ventilation) matches your blood flow (Perfusion) is essential. In healthy individuals, exercise makes more blood flow to the top part of the lung due to the opening of more capillaries (tiny blood vessels), leading to more air moving in and out of your lungs. The perfect balance between your airflow and blood flow to exercise properly is close to a 1:1. As you exercise more, keeping this balance becomes difficult because your heart can’t meet the high demands of your muscles, creating a ventilation-perfusion mismatch. Some illnesses can cause this mismatch to happen earlier, leading to exercise tolerance. In people with heart problems, there’s less blood flow to the lungs which throws the balance off. On the other hand, in patients with lung diseases, they have problems with airflow leading to a different imbalance.[2][3]
Why do People Need Cardiopulmonary Fitness
According to the guidelines set by the American Heart Association (AHA) regarding exercise tests that involve both the heart and lungs (technically called cardiopulmonary exercise testing):
“Class 1 Indication” refers to the surest cases where this test is needed:
1) For people with heart failure who might need a heart transplant, this test helps doctors figure out how much exercise they can tolerate and if their treatment is working.
2) For people who get short of breath when they exercise but doctors aren’t sure why, this test helps in diagnosing the cause.
“Class 2a Indication” points to cases where this test could be helpful:
1) When other ways of estimating exercise capacity, like how long a person can exercise or how intense their workout is, are not reliable for various health reasons, this test can provide a more accurate measurement.
“Class 2b Indication” describes cases where this test might be useful:
1) When doctors need to evaluate how a patient responds to a treatment that should improve their ability to tolerate exercise.
2) In a cardiac rehabilitation program, where this test can help determine how intense the exercise training should be.
When a Person Should Avoid Cardiopulmonary Fitness
According to the American Heart Association’s guidelines, there are certain conditions under which a person shouldn’t undergo a CPET (a kind of stress test to examine your heart’s health):
Absolute Reasons (you definitely shouldn’t do it):
– If you’re experiencing unstable chest pain or had a heart attack in the past couple days.
– If you’re having uncontrolled irregular heartbeats that are causing symptoms or affecting blood flow.
– If you have symptoms of serious conditions affecting your aorta (the main artery in your body).
– If your heart failure is uncontrolled.
– If you recently had a blood clot or blockage in your lungs.
– If you have inflammation in the heart or its outer layer.
– If you have a severe full-body infection and are showing symptoms.
Relative Reasons (you might want to avoid depending on the severity):
– If you have moderate narrowing of your heart valves.
– If you have a disease where your heart muscle becomes abnormally thick.
– If you regularly experience irregular heartbeats.
– If your main coronary artery (supplies blood to your heart) is narrowed.
– If you’re dealing with severe lung problems or untreated severe high blood pressure in your arteries.
– If your heart’s electrical signal is greatly affected, a condition known as high degree AV block.
Equipment used for Cardiopulmonary Fitness
A metabolic cart is a scientific tool that measures how your body exchanges and uses gases during metabolism, which is the process your body uses to convert food into energy. It’s important that these tests are performed accurately, which requires sticking to some pre-established calibration standards that ensure the equipment works correctly. Even though there are different types of metabolic carts which might slightly change the calibration process, it is essential to follow the specific instructions provided by the equipment maker. In addition to this, a guideline from the American Heart Association, as stated in Balady et al.’s scientific paper, should be abided by.
Also, it is important to have emergency medical equipment close by and ready to use during a metabolic cart procedure. This equipment includes:
* A crash cart, a movable chest of drawers that contains emergency medical supplies, including a device (the cardioverter-defibrillator) that can give your heart an electric shock to help it return to its normal rhythm if needed.
* An Ambu bag and mask, a device that can be used to help you breathe.
* An oxygen hook up to deliver oxygen.
* A suction device to clear your airway if needed.
* Supplies to start an IV, a tube that can deliver medicine or fluids directly into your veins.
Who is needed to perform Cardiopulmonary Fitness?
You may come across different medical professionals during your treatment. These professionals include a clinical exercise physiologist and a supervising heart doctor (also known as a cardiologist or electrophysiologist). A clinical exercise physiologist has a master’s degree or the equivalent qualification from the American College of Sports Medicine. They are trained to understand how exercise affects our bodies, and specifically our hearts.
Your care might also involve a cardiologist or electrophysiologist. These are doctors who specialize in treating issues related to the heart and its electrical system. They supervise your treatment to ensure everything goes as planned.
In addition, there could be nursing staff involved in your care. Their involvement largely depends on the policies and protocols of the hospital or healthcare center, especially in response to adverse or unexpected events during treatment. Their main task is to look after your needs, monitor your health, and step in if any problems arise.
Preparing for Cardiopulmonary Fitness
It’s very important to pick the right exercise routine to get the most accurate results. While there are many exercise plans to choose from, doctors should create a custom plan for each patient. This plan should be designed to make the patient tired in around 8 to 12 minutes. Two of the most common types of routines are either step by step or stable work plans.
In a step by step plan, the intensity of the exercise increases gradually. This increase happens at set intervals for each minute of different parts of the exercise routine. This kind of plan is often called a ramp protocol.
How is Cardiopulmonary Fitness performed
CPET stands for Cardiopulmonary Exercise Testing. This test consists of several parameters that measure how your heart and lungs work during exercise. Here’s a simple explanation of these parameters:
Peak VO2 or Maximal Oxygen Uptake measures how much oxygen your muscles use during exercise. It represents how fit you are – the more oxygen your muscles can use, the fitter you are. The amount of oxygen your muscles can use increases as you exercise harder, up until your heart can no longer supply enough blood to your muscles, which is when we reach a plateau. It’s normal for Peak VO2 to decrease with age after 30 years old.
VO2 is calculated using the Fick equation, trying to measure cardiac output and differences in oxygen content in our arteries and veins. VO2 lower than 80% of what’s expected for your age and sex might indicate heart or lung disease, or it could mean you need to do more exercise.
Oxygen Pulse is the amount of oxygen used by your tissues every time your heart beats. A low oxygen pulse might indicate that your heart can’t pump enough blood during exercise, which could mean there’s a problem with your heart.
Your Heart Rate should increase with exercise but there’s a maximum rate based on age. If your heart rate doesn’t increase as expected, it might mean there’s a problem with your heart.
Cardiac Output is the volume of blood your heart pumps out every minute. During exercise, it can increase up to five times your resting value. If it can’t increase as expected, it might indicate a heart problem.
Ventilatory Anaerobic Threshold (VAT) is the point at which your body can’t supply enough oxygen to your muscles and starts using anaerobic (without oxygen) metabolism. A VAT lower than 40% of your Maximal Oxygen Uptake is considered abnormal and might mean you’re unfit or have a heart or lung problem.
Ventilatory Efficiency measures how efficiently your body eliminates carbon dioxide during exercise. An increased VE/VCO2 slope may indicate heart failure.
Respiratory Exchange Ratio (RER) shows how your body is using fuel during exercise. It measures the ratio of carbon dioxide eliminated relative to oxygen consumed. The higher the RER, the harder your body is working.
Oxygen Uptake Efficiency Slope (OUES) represents how efficiently your body takes up and uses oxygen during exercise. The steeper the slope, the more efficient your oxygen uptake.
Depending on these parameters, issues with the heart, lungs, muscles or a lack of fitness (deconditioning) might be found. Overweight individuals might also show specific findings on the CPET.
Possible Complications of Cardiopulmonary Fitness
The most severe health risks can include dangerous irregular heartbeats during exercise (a too-fast beating heart, quivering heartbeats, or an extremely slow heart rate), physical injuries, unstable blood pressure and heart rate, or a sudden blockage of blood supply to the heart. These situations need immediate medical attention and treatment. Other possible complications could be less serious, but still troubling, types of uneven heartbeats, fainting (including fainting caused by a sudden drop in heart rate and blood pressure), stroke, or a brief period of reduced blood flow to the brain.
What Else Should I Know About Cardiopulmonary Fitness?
There can be many health issues that make it difficult for people, both those who are generally healthy and those with other health conditions, to exercise. These issues may be well-known, but some might be less obvious. This is where testing the ability and efficiency of the heart and lungs (known as “cardiopulmonary fitness testing”) comes into play. This type of testing can help to pinpoint the root cause of why exercise might be hard for someone. It also helps doctors better predict recovery times after surgery or treatment.
This kind of test, when used alongside the other traditional tools doctors use to investigate health issues, is considered the best and most precise way to study how your heart and lungs are functioning. That’s why experts often call it the “gold standard” of these types of tests.