Diagnostic Tests:

Despite the widespread incidence and seriousness of COPD, 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 COPD. In one study, nearly half of patients over age 60 who regularly smoked had COPD. Anyone who has a chronic cough, increased phlegm production, or breathing difficulty that gets worse over time should be checked for the disease.

Medical and Personal History

The doctor will request a history that evaluates the patient's risk factors. Risk factors include:

• Past and present smoking
• Exposure to industrial pollutants at work
• Family history of alpha-1 antitrypsin deficiency
• Low exercise capacity (such as trouble climbing stairs or difficulty walking for more than a certain distance)
• Past and present smoking

Physical Examination

Appearance. There are usually no changes in physical appearance in people with mild-to-moderate COPD. In advanced COPD, patients with emphysema may be wasted and thin, with normal-colored pink skin. Those with chronic bronchitis may have bluish lips and fingers, be obese, and may have swollen feet and legs. Breathing may be rapid and shallow, done through pursed lips, and it may take longer to breathe out.

The patient will be asked to cough and produce phlegm, if possible.

Chest Examination. The physician will next perform a simple examination of the chest area with a stethoscope to listen for:

• Crepitations, a noise resembling a paper bag being rumpled
• Reduced or distant breath sounds
• Signs of pulmonary hypertension
• Wheezing or gurgling sounds

Other findings may include:

• Breathlessness when the patient lies flat
• Increased pressure in the veins

Pulmonary Function Tests (Spirometry)

The best tests for diagnosing COPD and seeing how well it responds to treatment are pulmonary function tests. The gold-standard test for patients with respiratory symptoms such as shortness of breath is spirometry. Spirometry measures the volume and force of air as it is exhaled from the lungs. It measures airway obstruction, can identify COPD early, and the results are standardized so they are always consistent.

The patient is asked to breathe in and breathe out forcefully into an instrument. This is repeated several times. The force of the air is then measured. From the results, the physician determines two important values:

The forced vital capacity (FVC). FVC is the maximum volume of air that a patient can breathe out with force. It indicates lung size, elasticity, and how well the air passages open and close.

The forced expiratory volume in one second (FEV1). FEV1 is the maximum volume of air that a patient can breathe out in 1 second after breathing in fully. Airflow is considered to be limited if the forced breath out stays low over 1 second. People with COPD have a decline in FEV1 over time. FEV1 is measured as "percent of predicted:"

• Moderate COPD is an FEV1 50 - 80% of predicted.
• Severe COPD is an FEV1 30 - 50% of predicted.
• The ratio of FEV1 to FVC (FEV1/FVC) is less than 70% of normal, regardless of whether the patient has an FEV1 greater than 80% or less than 50%.

Spirometry is a painless study of air volume and flow rate in the lungs. Spirometry is frequently used to evaluate lung function in people with diseases such as asthma or cystic fibrosis.

Tests for Measuring the Ability of the Lung to Exchange Oxygen and Carbon Dioxide

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 often indicate chronic bronchitis, but not always emphysema. A blood gas analysis that shows very low oxygen levels is useful for determining which patients would benefit from oxygen therapy (see below). This procedure typically involves drawing blood from an artery in the wrist.

Pulse Oximetry Test. A safe and painless test for measuring oxygen in the blood is called pulse oximetry, which involves placing a probe on the finger or ear lobe. The probe emits two different lights. The amount of each light the blood absorbs is related to how much oxygen the red blood cells carry. This test measures only oxygen in the blood, however, and not carbon dioxide. Results should be taken together with other tests to determine the need for medication or oxygen therapy.

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 (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.

Exhaled Breath. The measurement of nitric oxide (NO) in exhaled breath can be a simple method of diagnosing COPD and monitoring the effects of treatment. In most patients with COPD, no levels are below normal. Levels above normal in a patient with COPD indicate that the person also has asthma.

Imaging Tests

Chest X-Rays. Chest x-rays are often performed, but they are not very useful for detecting early COPD. By the time an x-ray reveals COPD, the patient is already well aware of the condition. X-rays can look for growths in the lungs to rule out other diseases, however.

Clear signs of COPD on x-ray include the following:

• Abnormally large amounts of air spaces in the lung
• A flattened diaphragm
• A smaller heart (however, if the person has heart failure, the heart becomes enlarged and there may not be signs of overinflated lungs)
• Exaggerated lung inflation in upper areas
• Larger amounts of air in the lower lungs in patients with emphysema related to alpha-1 antitrypsin deficiency

Chest x-rays are rarely useful for diagnosing chronic bronchitis, although they sometimes show mild scarring and thickened airway walls.

Computed Tomography. Computed tomography (CT) scans can accurately assess the severity of COPD and may be used to determine the size of the air pockets (bullae) in the lungs.

Other Tests for COPD

Noninvasive Methods for Determining Severity. Questionnaires and short exercise tests are very useful for determining the severity of COPD.

Test for alpha-1 antitrypsin deficiency. Physicians will typically test for the enzyme alpha-1 antitrypsin in COPD patients who are nonsmokers and who develop emphysema in their 30s.

Additional Blood and Sputum Tests. Additional tests may be required if the physician suspects other medical problems. If the person has pneumonia, for instance, blood and sputum tests and cultures may be performed to determine the cause of infection.

Bronchodilator Challenge. Using a bronchodilator can usually relieve the symptoms of asthma. However, patients with COPD typically have a limited response to bronchodilation. A bronchodilator challenge test may help distinguish between the two diseases. Some patients with COPD experience limited and temporary improvement in FEV1 30 - 45 minutes after inhaling medication from a metered dose inhaler. However, their airflow remains poor.