For a listing of medications to stop and the length of time to stop before having any of the following tests - click here.
Spirometry is a measurement of forced expiration. The patient inhales maximally, filling his or her lungs to Total Lung Capacity, and then exhales forcefully into a device called a spirometer. The spirometer measures volume and time, and from this several important parameters may be calculated:
- FVC (Forced Vital Capacity) - the maximum amount of air able to be exhaled on a single breath
- FEV1 (Forced Expired Volume in 1 Second) - the amount of air exhaled in the first second
- FEV1/FVC - the percentage of the FVC exhaled in the first second
The last quantity (FEV1
/FVC) is particularly helpful in characterizing airways obstruction.
Spirometry after Bronchodilator
Spirometry, repeated after the administration of a bronchodilator (most often albuterol [Ventolin, Proventil]). Generally, an increase of more than 10% in either FVC or FEV1 is considered a positive response.
The same general test as spirometry, except the data collected are plotted in a different way, showing flow vs. volume. The patterns thus revealed may indicate the site and nature of any airways obstruction.
Single Breath Diffusing Capacity
The single breath diffusing capacity, or DLCO, is a measure of the ability of the lungs to diffuse oxygen into, and carbon dioxide from, the bloodstream. The test is performed by having the patient complete the following steps:
- expire all the way to Residual Volume
- inspire all the way to Total Lung Capacity,breathing from a supply of test gas
- hold breath for ten seconds
- expire forcefully
The concentrations of certain gases present in the "test gas" is measured prior to the test. The initial portion of the final expirate is discarded, and a portion of the remainder is analyzed. Generally, the difference between the concentrations present before the breathhold and after the breathhold indicates the amount of gas that diffuses through the lungs and into the bloodstream.
Body Plethysmographic Lung Volumes
This test measures the same things as does Helium Dilution Lung Volumes, but in a very different way. The patient sits in a clear rigid chamber, breathing through a valve. At some point in the breathing cycle, the valve is closed for a few seconds and the patient is asked to pant (although no breathing will occur since the valve is closed). Each time the patient tries to pant out, the gas in the lungs is decompressed slightly and the gas in the box surrounding the patient is compressed slightly. When the patient tries to pant in, the opposite occurs. By measuring the pressure changes in the lungs and in the box, the amount of gas in the patient's lungs may be calculated.
This test estimates the amount of oxygen in the arterial blood by shining a light through a fingertip. Because blood that holds a lot of oxygen is a different color than less oxygenated blood (oxygenated blood is bright red, otherwise it is purple), the device is able to estimate the blood's oxygen content.
Less Common Tests
Arterial Blood Gas Analysis
This test measures the amounts of oxygen and carbon dioxide and the pH of an arterial blood sample. Most often the blood sample is obtained in the laboratory via either the radial artery (near the wrist) or the brachial artery (near the inside of the elbow). A blood gas analyzer measures and reports the pO2
(the amount of oxygen present), the pCO2
(the amount of carbon dioxide), and the pH of the blood.
In a Bronchial Challenge, a patient performs repeated spirometry tests following inhalation of a medication. At Hammond-Henry we use Aridol. Aridol is an indirect challenge test for asthma. The Aridol lung function test helps doctors more accurately determine the severity of a patient's airways inflammation. The 15-25 minute test uses powdered mannitol, which the patient inhales in increasing doses. In asthmatic patients, this causes the airways to narrow and contract, which is detected by measuring the amount of air a person can exhale in one second. The smaller the dose required to cause contraction, the more severe the patient's asthma.
Frequently Asked Questions
How do I get Complete Pulmonary Function (CPFT) Test or a Spirometry?
You should ask your doctor to order it for you. The equipment to perform test is very simple, it looks likes a phone booth.
How will l know if my spirometry test results are normal?
Normal values for a CPFT vary, depending on your age, height, gender and race. Your numbers will be higher in comparison to others if you are younger, taller and a male. Also Caucasians have higher numbers than African Americans or Asians. Therefore, the numbers are presented as a percentage of the average expected in someone of your age, height, gender and race. This is called percent predicted.
What should I do if my numbers are abnormal?
You should talk to your doctor. There are many possible reasons for an abnormal test result, and your doctor may want to order more tests to find the reason. If you smoke, stop smoking. Stopping smoking is the single most important intervention you can make to improve lung and overall health.
If my test numbers are abnormal, is there anything I can do to make them better?
You should talk to your doctor. What you can do to make your lungs better will depend on why your numbers are abnormal. Obviously, if you smoke, stop smoking. It is important to preserve the lung function you have. Certain medication may help to improve your lung function, depending on the cause of the problem. Although there is no current cure for COPD, many drugs can partially improve airflow obstruction and associated symptoms of COPD.
If my numbers are abnormal, what else should I do to preserve my health?
Stop smoking. Eat a healthy diet. Exercise regularly, even if only moderately, under the direction of your doctor. Talk to your doctor about whether you should have the influenza vaccine every fall, the pneumococcal vaccine every five years, routine bronchodilators, maintenance inhaled corticosteroids,or antibiotics for acute worsening of symptoms. Ask if Pulmonary Rehab might be appropriate for you.
Hammond-Henry Hospital Cardiopulmonary Services
600 North College Avenue
Geneseo, IL 61254