Diagnosis
A doctor usually can tell whether a person has a lung or airway disorder based on the medical history and physical examination. Diagnostic procedures are used to confirm the diagnosis, determine the extent and severity of the disease, and help in planning treatment.
Medical History and Physical Examination
A doctor first asks the person about symptoms.
Next, the doctor asks the person about past infections; previous exposure to chemicals; use of drugs, alcohol, and tobacco; home and work environments; travels; and recreational activities. A doctor also asks the person about whether family members have had lung or airway disease and any other diseases that may affect the lungs or airways.
During the physical examination, a doctor notes the person's weight and overall appearance. The person's general mood and feeling of well-being, which also may be affected by lung or airway disease, are also noted. A doctor may ask a person to walk around or climb a flight of stairs to see if either activity causes shortness of breath.
Assessing skin colour is important because pallor or cyanosis may indicate anaemia or poor blood flow. These findings can indicate that the skin is receiving inadequate oxygen from the blood because of lung or airway disease. Fingers are examined for evidence of clubbing.
A doctor observes the chest to determine if the breathing rate and movements are normal. By tapping (percussing) the chest, a doctor can determine if the lungs are filled with air, which is normal, or if they contain fluid, which is abnormal. Using a stethoscope, a doctor also listens to the breath sounds to determine whether airflow is normal or obstructed and whether the lungs contain fluid as a result of respiratory failure or pneumonia.
In addition to examination of the chest, a complete physical examination may be needed, because many disorders not related to the lungs first present with evidence of lung problems.
Lung Function Tests
Lung function tests evaluate how well your lungs work. The tests determine how much air your lungs can hold, how quickly you can move air in and out of your lungs, and how well your lungs add oxygen and remove carbon dioxide from your blood. The tests can diagnose lung diseases and measure the severity of lung problems.
Spirometry is the first lung function test done. It measures how much and how quickly you can move air out of your lungs. For this test, you breathe into a mouthpiece attached to a recording device (spirometer). The information collected by the spirometer may be printed out on a chart called a spirogram.
Gas diffusion tests
Gas diffusion tests measure the amount of oxygen and other gases that cross the lungs' air sacs (alveoli) per minute. These tests evaluate how well gases are being absorbed into your blood from your lungs.
Gas diffusion tests include:
- Arterial blood gases, which determine the amount of oxygen and carbon dioxide in your bloodstream.
- Carbon monoxide diffusing capacity (also called transfer factor, or TF), which measures how well your lungs transfer a small amount of carbon monoxide (CO) into the blood.
Two different methods are used for this test. If the single-breath or breath-holding method is used, you will take a breath of air containing a very small amount of carbon monoxide from a container while measurements are taken.
In the steady-state method, you will breathe air containing a very small amount of carbon monoxide from a container.
The amount of carbon monoxide in your arterial blood is then measured. Diffusing capacity provides an estimate of how well a gas is able to move from your lungs into your blood.
Lung function results are measured directly in some tests and are calculated in others. No single test can determine all of the lung function values, so more than one type of test may be done. Some of the tests may be repeated after you inhale medication that enlarges your airways.
Lung function tests are done to:
- Determine the cause of breathing problems.
- Diagnose certain lung diseases, such as asthma or chronic obstructive pulmonary disease (COPD).
- Evaluate a person's lung function before surgery.
- Monitor the lung function of a person who is regularly exposed to substances such as asbestos or radon that can damage the lungs.
- Monitor the effectiveness of treatment for lung diseases.
How It Is Done
Lung function tests are usually done in special exam rooms that have all of the lung function measuring devices. The test is usually done by a specially trained respiratory therapist or technician. For most of the lung function tests, a patient will wear a nose clip to make sure that no air passes in or out of the nose during the test. The patient is then be asked to breathe into a mouthpiece connected to a recording device.
The accuracy of the tests depends on the patient's ability to follow all of the instructions. The therapist may strongly encourage the patient to breathe deeply during some of the tests to get the best results.
The testing may take from 5 to 30 minutes, depending upon how many tests are done.
Risks
Lung function tests present little or no risk to a healthy person.
Results
Lung function tests evaluate how well your lungs work. The normal value ranges for lung function tests will be adjusted for the patient's age, height, sex, and sometimes weight and race. Results are often expressed in terms of a percentage of the expected value.