Chronic Obstructive Lung Disease
DescriptionAn in-depth report on the causes, diagnosis, treatment, and prevention of COPD -- emphysema and/or chronic bronchitis.
Alternative NamesAlpha-1 Antitrypsin Deficiency; Bronchitis: Chronic; Chronic Bronchitis; Chronic Obstructive Pulmonary Disease; Emphysema
In spite of the widespread incidence and seriousness of chronic obstructive lung disease, studies strongly suggest that it is underdiagnosed, especially in women. Some experts recommend that any adult smoker who complains of a daily cough should be screened for COLD. In one 2002 study, nearly half of patients over 60 who regularly smoked had COPD.
Medical and Personal History
The physician will request a history that assesses the patient's risk factors. They include past and present smoking, low exercise capacity (e.g., whether the patient has trouble climbing stairs, the distance he or she can walk), and exposure to any industrial pollutants.
Appearance. The appearance of the patients may be a clue to the condition. Bluish skin tone and swelling in the legs ("the blue bloater") suggests chronic bronchitis. Healthy skin tone but having an inflated chest ("the pink puffer") suggests emphysema.
The patient will also be asked to cough and produce sputum, if possible.
Chest Examination. The physician will next perform a simple examination of the chest area. Using a stethoscope, the physician will listen to the patient's breathing:
Pulmonary Function Tests (Spirometry)
The best tests for determining the presence and managing the response to treatment of chronic obstructive lung disease are pulmonary function tests, most often spirometry. Spirometry measures the volume and force of air as it is exhaled from the lungs. The patient is asked to breathe in and to exhale forcefully into an instrument several times. The force of the air is then monitored and measured.
Using the results, the physician determines two important values:
Calculating a ratio of FEV1 to FVC is the best method for determining the presence and severity of COLD. The severity of airway obstruction may be graded by the percentage of the patient's predicted FEV1:
Tests for Measuring the Ability of the Lung to Exchange Gases
Arterial Blood Gas. The physician may request an arterial blood gas test to determine the amount of oxygen and carbon dioxide in the blood (its saturation). Low oxygen (hypoxia) and high carbon dioxide (hypercapnia) levels are often indicative of chronic bronchitis, but not always of emphysema. A blood gas analysis that shows very low oxygen levels (measured as PO2) is useful for determining which patients would benefit from oxygen therapy. This procedure typically draws blood from an artery in the wrist, which can be painful.
Pulse Ox Test. A less painful test for measuring oxygen in the blood is called a pulse ox, which involves placing a probe on the finger or ear lobe. When blood is fully saturated with oxygen, it forms a compound called oxyhemoglobin, which gives blood its bright red color. When blood has insufficient oxygen, it turns a bluish color (called cyanosis). This test only measures oxygen in the blood, however, and not carbon dioxide, so it is not useful in determining candidates for long-term supplemental oxygen.
Carbon Monoxide Diffusing Capacity. The lung carbon monoxide diffusing capacity (DLCO) test determines how effectively gases are exchanged between the blood and airways in the lungs. Patients should not eat or exercise before the test and they should not have smoked for 24 hours. The patient inhales a mixture of carbon monoxide, helium, and oxygen and holds his or her breath for about 10 seconds. The gas levels are then analyzed from the exhaled breath. Results can help physicians differentiate emphysema from chronic bronchitis and asthma. Patients with emphysema have lower DLCO results, indicated by a reduced ability to take up oxygen. Such results are also important in helping to determine appropriate candidates for lung reduction surgery. (Carbon monoxide levels that are 20% or less than predicted values pose a very high risk for poor survival.)
Chest X-Rays. Chest x-rays are often performed, but they are not very useful for detecting early COLD. By the time an x-ray reveals the disease, the patient is well aware of the condition.
Clear signs of emphysema include the following:
X-rays are rarely useful for diagnosing chronic bronchitis, although they sometimes show a so-called dirty chest (mild scarring and thickened airway walls).
Computed Tomography. Computed tomography (CT) scans can accurately assess the severity of COLD and may be used to determine the size of the air pockets (bullae) in the lungs. This imaging technique may even be useful for assessing mild COLD.
Other Tests for Chronic Obstructive Lung Disease
Noninvasive Methods for Determining Severity. Questionnaires and short exercise tests are very useful for determining the severity of COLD.
Test for ATT. Physicians will typically test for the protective enzyme, alpha 1-antiprotease (ATT or antitrypsin), which is often deficient in COLD patients (although asthma patients may also have low levels).
Additional Blood and Sputum Tests. Additional tests may be required if the physician suspects other medical problems. If pneumonia is present, for instance, blood and sputum tests and cultures may be performed to determine the cause of infection.