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Cardiopulmonary Exercise Testing (CPX)
Cardiopulmonary exercise testing is a non-invasive and
objective method of evaluating both cardiac and pulmonary
function. It allows a very accurate assessment of possible
cardiac failure. Cardiac function is evaluated in terms of
aerobic capacity and respiratory function is evaluated by
measuring direct airflow in the lungs during exercise.
CPX may be used in all age groups to evaluate cardiac
function objectively. It may be used to evaluate the
treatment of cardiac disease, whether from myocardial
ischemia or cardiac failure. Respiratory function may be
evaluated dynamically by measuring the amount of air
entering and leaving the lungs during exercise thus
detecting exercise induced asthma as well as restrictive and
obstructive lung disease. Additional measurements can be
made which can assist in diagnosing suspected pulmonary
artery hypertension.
The patient is connected to a computerized 12-lead ECG
machine that monitors both the heart rate and rhythm. A
small mouthpiece, connected to a special machine, is placed
in the mouth and small clamp is place on the nose. The
patient is then exercised on a stationary bicycle ergometer.
The patient is then asked to pedal the ergometer against
periodically increasing resistance. Sometimes a standard
treadmill machine may be used instead and the patient is
asked to walk with an increasing incline, increasing speed,
or both. While the patient is exercising, the inhaled and
exhaled air is sampled and analyzed for oxygen consumption
and carbon dioxide production. The ECG is also analyzed for
any changes that would suggest decreased blood flow to the
heart muscle. The test is usually planned to last around 10
minutes once the exercise portion is started.
Before the Test.
In general, you should not eat or smoke for at least two
hours before the test, but follow your doctor's specific
instructions. Wear comfortable shoes or sneakers and shorts
or loose fitting clothing. Women will be asked to wear a
patient gown. When you arrive, you will be greeted by our
respiratory therapist and asked to complete a medical
history sheet and a consent form.
How is a CPX performed?
Your skin will be prepared with a mild abrasive pad and ECG
patches and wires are attached to your chest. A blood
pressure cuff will be placed on an arm, and a baseline
electrocardiogram and blood pressure are recorded. A small
mouthpiece, connected to a special machine is placed in your
mouth and a clamp is placed on your nose. After the doctor
arrives, he or she will determine at what level you should
start exercising at and you will begin pedaling on the
bicycle ergometer or walking on the treadmill. Your ECG,
blood pressure, and inhaled and exhaled air will all be
monitored and measured throughout your test as well as into
the recovery period.
If you develop any dizziness, a drop in blood pressure,
severe chest pain, severe shortness of breath, or cardiac
arrhythmias during your test, it will most likely be
stopped early. Otherwise the test will continue until
you reach an endpoint that is determined by the doctor.
What are the risks of CPX?
As with other types of exercise testing, CPX is really
quite safe. The risk of death is very low, and careful
monitoring of your blood pressure and ECG during the test,
further adds to its safety. Sometimes, however, any type
of exercise test can bring on a heart attack or cardiac
rhythm problem. These can be a result of insufficient
blood flow to the heart muscle. The staff is trained to
deal with these problems and the room in which you perform
the test is equipped with a defibrillator and emergency
medications.
After the test.
Depending on the results, you will rest until your heart
rate, blood pressure, and other vital signs return to
normal. If there are no complications, the blood pressure
cuff and electrodes are removed and you may dress and depart
the office.
Obtaining the results.
The test results will need to be analyzed by the doctor.
You will be asked to make a follow up appointment with your
doctor to discuss the results and what their significance
are to your health. Any further treatment or testing
recommendations will be made at that time.
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