Chronic Obstructive Pulmonary Disease (COPD) (cont.)

COPD usually is first diagnosed on the basis of a medical history which discloses many of the symptoms of COPD and a physical examination which discloses signs of COPD. Other tests to diagnose COPD include chest X-ray, computerized tomography (CAT or CT scan) of the chest, tests of lung function (pulmonary function tests) and the measurement of carbon dioxide and oxygen levels in the blood.

COPD is often suspected in chronic smokers who develop shortness of breath with or without exertion, have chronic persistent cough with sputum production, and frequent infections of the lungs such as bronchitis or pneumonia. Sometimes COPD is first diagnosed after a patient develops a respiratory illness necessitating hospitalization. In reality, COPD should be suspected in all chronic smokers because often they will only develop symptoms after significant lung damage occurs. Some physical findings of COPD include enlarged chest cavity and wheezing. Faint and distant breath sounds are heard when listening to the chest with a stethoscope. Air is trapped in the lungs from the patient's inability to empty their lungs with exhalation. This extra air dampens the sounds heard and results in the overinflated chest cavity.

In patients affected predominantly with emphysema, the chest X-ray may show an enlarged chest cavity and decreased lung markings reflecting destruction of lung tissue and enlargement of air-spaces.

In patients with predominantly chronic bronchitis, the chest X-ray may show increased lung markings which represent the thickened, inflamed and scarred airways. Computerized tomography (CT or CAT scan) of the chest is a specialized X-ray that can accurately demonstrate the abnormal lung tissue and airways in COPD.

Chest X-rays and CT scans of the chest also are useful in excluding lung infections (pneumonia) and cancers. CT scan of the chest usually is not necessary for the routine diagnosis and management of COPD, but can be helpful in evaluating the extent of emphysematous change as well as detecting early lung cancers.

The most commonly used pulmonary function test is spirometry, a test which quantitates the amount of airway obstruction. During spirometry, the patient takes a full breath and then exhales fast and forcefully into a tube connected to a machine that measures the volume of expired air. The FEV1 (the volume of air expired in 1 second) is a reliable and useful measure of airflow obstruction. This is compared to the total amount of air blown out of the lungs, the forced vital capacity (FVC). The ratio of the FEV1 to the FVC is usually 70%. When obstruction is present, this ratio is reduced; the lower the RATIO, the greater the airway obstruction. The FEV1 can be determined again after treatment with bronchodilators. Improvement in FEV1 after bronchodilator treatment means that airway obstruction is reversible. Demonstrating improvement in FEV1 also helps doctors select the proper bronchodilators for patients. Measurements of FEV1 and FVC can be repeated over time to determine how rapidly airway obstruction is progressing.

Oxygen and carbon dioxide levels can be measured in samples of blood obtained from an artery, but this requires inserting a needle into an artery. A less invasive method to measure oxygen levels in the blood is called pulse oximetry. Pulse oximetry works on the principle that the degree of redness of hemoglobin (the protein in blood that carries oxygen) is proportional to the amount of oxygen, that is, the more oxygen there is in blood, the redder the blood. A probe (oximeter) is placed around a fingertip. On one side of the finger the probe shines a light. Some of the light is transmitted through the fingertip, and the transmitted light is measured on the opposite side of the finger by the probe. Depending on the redness of the blood within the fingertip (that is, the amount of oxygen in the blood) different shades of red are transmitted through the fingertip. Thus, by measuring these differences in the red light, it is possible to determine the amount of oxygen in the blood.

Another very effective and simple test used to monitor COPD is called the six minute walking test (6MWT). The patient is asked to walk on a level surface at their own pace for six minutes. There is a very prescribed script that is utilized when performing this test. The patient is informed about the time left to complete the test, but no encouragement is offered. The patient may stop and rest at any time during the study. The distance traveled is measured and is a very accurate index of the state of health and effectiveness of therapy.

Source: MedicineNet.com
http://www.medicinenet.com/chronic_obstructive_pulmonary_disease_copd/article.htm