For a listing of medications to stop and the length of time to stop before having any of the following tests - click here.
Common Tests
Spirometry
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.
Flow-Volume Loops
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.
Pulse Oximetry
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.
Bronchial Challenge
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.
Cardiopulmonary Services of Hammond-Henry Hospital
600 North College Avenue
Phone: (309) 944-9169
Email Cardiopulmonary at brucemace@hammondhenry.com