Lungs – Tests for Diagnosis of COPD

COPD is short for Chronic Obstructive Pulmonary Disease. COPD includes both chronic bronchitis and emphysema. These two bring about narrowing of the air passage in the lungs and hinder the intake of oxygen and release of carbon dioxide. They cause this in their own ways and therefore a diagnosis at a deeper level is required to identify the root of the symptoms manifested.

To begin with – a preliminary test for diagnosis of COPD is done by measuring oxygen levels in the blood. This is done by measuring volume of air flowing into the lungs, and a few other parameters.

Spirometry test: This is the first of a series of tests for diagnosis of COPD and it measures the capacity of the lungs. The patient is made to breathe-in deep and breathe-out into a tube. The volume of air collected in the tube is measured.

The variables FEV1 standing for Forced expiratory volume after 1 second, FVC standing for Forced Vital Capacity, and FEF25-75 for Forced Expiratory Flow at 25%-75%, are calculated. These calculations help the physician come to conclusion about the presence or otherwise of COPD in the patient. The test is repeated several times.

Post-bronchodilator spirometry test: For this test, a bronchodilator is used. The patient uses bronchodilator to create more room in the air passages of his lungs. This is immediately followed by a normal spirometry test. Once again calculations are worked out for the physician to interpret.

This two pronged test, one, helps confirm the diagnosis of COPD, two, it gives a clue to the physician as to whether the patient’s reduced lung capacity can be increased through bronchodilators.

Lung volume test: This test involves measuring the lung capacity using body plethysmography or gas dilution. Height, weight, age, gender parameters are also included in the test. The results are compared with the average of normal people.

In body plethysmography the patient is let into an air sealed compartment. The patient is made to breathe-in and breathe-out via a tube. The tube is attached to the equipment which records pressure changes on a plethysmograph. This graph is then inferred for, for the lung capacity of the patient.

For gas dilution, the patient breathes in nitrogen gas or helium gas. The level of dilution of air in the lungs is measured to infer on the lung capacity of the patient.

Diffusion capacity test: For the test, the afflicted is made to breathe-in a small volume of carbon monoxide gas. This is immediately followed by taking of blood sample of the afflicted. The blood sample is tested for presence of carbon monoxide. The diffusion rate of the gas helps diagnose presence of emphysema.

Oximetry test: This test measures arterial blood gas (here, oxygen) as a method of diagnosis of COPD. This involves syringing out blood from the arteries which is a torture. A simple but less accurate method uses an instrument which directs a light through the afflicted person’s finger. The light received on the other side of the finger, distortions in the light help infer the amount of oxygen in the blood.

On completion of all the above tests for diagnosis of COPD, the physician will be able to conclude the presence or otherwise of COPD. The physician will direct you to further tests for chronic bronchitis and emphysema, if tested positive for COPD.