November 1, 2008 — Pulmonologists have found that a diagnostic test for asthma--the exhaled nitric oxide test is a quick and easy way to determine whether inhaled corticosteroids (medications that reduce irritation and inflammation) will relieve a patient's chronic cough. The patient breathes into an analyzer in order to measure inflammation in the lungs' bronchial tubes. Abnormal scores indicate that the patient has asthma or possibly non-asthmatic eosinophilic bronchitis.
Coughs are one of the most common reasons patients see a doctor. For patients with chronic ones, diagnosis and treatment can be frustrating; but new, simple test could help millions crack the mystery of their persistent problem.
Registered nurse Judy Rueggs suffers from a chronic cough. "Sometimes, my patients will say to me, 'You need to see a doctor," said Rueggs.
Today's a good day for Rueggs. She's trying a new test that's helping others find relief. The exhaled nitric oxide test at the Mayo Clinic has major advantages over a more commonly used test, the methacholine challenge. "It's simpler, it's quicker, [it's] non-invasive, [and it has] no side effects," said Peter Hanh, M.D., a pulmonologist at the Mayo Clinic in Rochester, Minn.
The test measures inflammation in the lungs' bronchial tubes. An abnormal score indicates if a patient has a treatable cause of chronic cough. Pulmonologists like Dr. Hahn say the four main causes of chronic cough are post-nasal drip, acid reflux, asthma and a type of non-asthmatic bronchitis.
With just a few breaths, the new test allows doctors to find out which patients suffer from two treatable conditions, asthma and bronchitis.
"[By doing] this very simple, non-invasive test up front, we were able to find patients who were responsive to inhaled corticosteroids as a treatment for their cough," Dr. Hahn said.
Rueggs sees firsthand how this test helps her patients. "They think it's wonderful there's another test that can really zero in on their diagnosis," Rueggs said.
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 patientýs 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.
Editor's Note: This article is not intended to provide medical advice, diagnosis or treatment.