Diagnosis of Emphysema
To diagnose emphysema, the physician takes a complete patient and family medical history and performs a physical examination and diagnostic tests. The medical history includes important information about previous and current cigarette smoking and a history of symptoms. In patients who have a family history of emphysema, a blood test may be performed to detect alpha-1 antitrypsin deficiency.
During physical examination, the physician listens to the lungs with a stethoscope and looks for signs of emphysema (e.g., barrel chest, decreased breath sounds). If the medical history and physical examination suggest a diagnosis of emphysema, diagnostic tests may be performed.
Tests used to diagnose emphysema include the following:
- Blood tests (e.g., complete blood cell count [CBC], arterial blood gas [ABG])
- Imaging tests (e.g., chest x-ray, computed tomography [CT scan])
- Oximetry (noninvasive method to measure levels of oxygen in the blood)
- Pulmonary function tests (e.g., peak flow, spirometry)
Blood Tests & Emphysema Diagnosis
Blood tests can be used to rule out other conditions. For example, high levels of white blood cells may indicate infection (e.g., pneumonia). An arterial blood gas (ABG), which involves drawing blood from an artery instead of a vein, measures levels of oxygen and carbon dioxide in the blood. This test can be used to determine if oxygen therapy is needed.
Imaging Tests & Emphysema Diagnosis
In some cases, imaging tests are used to help diagnose or rule out other lung conditions (e.g., pneumonia, lung cancer) and to detect inflammation in the lungs. Chest x-rays often are performed when the medical history and physical examination suggest a diagnosis of emphysema.
Computed tomography (CT scan), also called computerized axial tomography (CAT scan), can detect inflammation in lung tissue earlier than standard chest x-rays. In CT scan, x-rays are taken from many different angles and processed through a computer to produce cross-sectional images of the lungs.
Oximetry & Emphysema Diagnosis
In oximetry, an electronic device called a pulse oximeter is attached to a part of the body (e.g., finger tip, ear lobe, forehead) and used to measure oxygen (O2) levels in the blood. Oxygenated blood is brighter red than oxygen-deprived blood, which is bluish-purple in color.
The pulse oximeter transmits beams of light through blood vessels (capillaries), measures differences in color, and calculates blood oxygen levels. The blood oxygen level then is displayed on an electronic screen as O2 saturation (O2 sat) rate. Normal rates are greater than 90 percent. Lower rates indicate a decrease in lung function.
Pulmonary Function Tests & Emphysema Diagnosis
Pulmonary function tests (PFTs) are used to measure air flow within the lungs and evaluate lung function. These tests can help to confirm a diagnosis of emphysema and determine the severity of the condition.
Pulmonary function tests include peak flow, spirometry, lung volumes, and diffusion capacity. Peak flow, also called peak expiratory flow rate (PEFR), uses a device that consists of a tube and a gauge to measure the maximum force with which a patient can exhale. Normal peak flow rates vary from person to person and low rates can indicate decreased lung function.
Spirometry measures the air capacity of the lungs. In this test, the patient inhales as deeply as possible, places a tube into the mouth that is attached to an apparatus called a spirometer (spirometry machine), and exhales as quickly and with as much force as possible. In most cases, this test is repeated three times to get an accurate measurement.
Spirometry measures a number of different values including the forced expiratory volume after one second (FEV1), the forced vital capacity (FVC), and the forced expiratory flow at 25–75 percent of maximum lung volume. If these rates are lower than expected for the patient's age, sex, height, and weight, decreased lung function is indicated.
Lung volume tests also may be performed to measure lung capacity and function. In these tests, the patient inhales and exhales into a machine that measures the total lung capacity (TLC) and residual volume following exhalation. Rates that are higher than normal can indicate emphysema.