ABOUT THE TEST: By using an inexpensive test intended to diagnose asthma, doctors are now able to quickly determine if corticosteroids will be an effective treatment for chronic cough. The test measures the presence of a gas called nitric oxide when a patient exhales. During the test, the patient exhales into an analyzer. A patient with asthma or non-asthmatic bronchitis will have an abnormal reading because the patient's airway is inflamed and irritated, which is causing the cough. Both diagnoses can be effectively treated using inhaled corticosteroids.
ABOUT THE LUNGS: The lungs are located in the chest cavity, and are protected by the rib cage. The lungs are responsible for the exchange of oxygen and carbon dioxide between the body and its surrounding environment. They are made of a spongy, elastic type of tissue filled with tiny holes or bubbles, each surrounded by a fine network of tiny blood vessels. This tissue stretches and contracts as you breathe. The total surface area of the lungs is about the size of a football field.
When you breathe in, the diaphragm and intercostals or chest wall muscles contract, causing the air to travel from your nose and mouth through the windpipe (trachea), then through large and small tubes in the lungs called bronchial tubes. At the end of these tubes are groups of tiny air sacs called alveoli. They have very thin walls filled with small blood vessels called capillaries. Oxygen passes from the air sacs into the blood vessels, and carbon dioxide -- the waste byproduct from the body's metabolism -- passes from the blood into the air sacs. The carbon dioxide is then expelled into the atmosphere when you exhale.
The rate of breathing is controlled by the nervous system, specifically respiratory centers located in the brainstem, or medulla. These centers are filled with nerve cells that automatically send signals to the diaphragm and intercostals muscles, causing them to contract and relax at regular intervals.