Medical Health Encyclopedia

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.)

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Imaging Tests

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.

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Clear signs of emphysema include the following:

• A flattened diaphragm.
• Exaggerated lung inflation in upper areas.
• Abnormally large amounts of air spaces in the lung.
• A smaller heart. (If heart failure is present, however, the heart size becomes normal and signs of overinflated lungs are not present.)
• A1AD-related emphysema patients show larger amounts of air in the lower lungs.