Diagnosis of Chronic Obstructive Pulmonary Disease (COPD)

Spirometry

Based upon a positive patient history and physical examination, the health care provider can develop a strong suspicion that the patient's signs and symptoms are most likely due to chronic obstructive pulmonary disease (COPD). Confirming the diagnosis of COPD, however, requires spirometry - a test that is performed to evaluate and measure lung function. This is a non-inavasive test that uses a device called a spirometer to measure the amount of air that is blown out of the lungs. During the test, the patient is asked to take a deep breath and then quickly blow it out into a mouthpiece that is attached to the spirometer until all of the air has been expelled from the lungs.

The following parameters of lung function are measured with spirometry:

• Forced Expiration Volume in One Second (FEV1) - This is a measure of the amount of air that can be expelled from the lungs in one second.
• Forced Vital Capacity (FVC) - This is a measure of the total amount of air that can be expelled from the lungs in a single breath.
• The FEV1/FVC ratio - This number is calculated by dividing the FEV1 by the FVC.

When testing patients with suspected COPD by spirometry, doctors can compare the patient's spirometry results to the predicted normal values for healthy people of a similar age, height, and gender. In general, airway obstruction is considered to be present if:

• The FEV1/FEC ratio is less that 0.7
• The FEV1 is less than 80% of the predicted normal value

Based on the results of spirometry measurements, people with COPD can be classified into one of the following three categories:

• Mild obstruction - if the FEV1 is between 65% and 79% of the predicted normal value

• Moderate obstruction - if the FEV1 is between 40% and 59% of the predicted normal value

• Severe obstruction - if the FEV1 is less than 40% of the predicted normal value