an inflammation of the lining of the bronchial tubes, the airways that connect the trachea (windpipe) to the lungs. This delicate, mucus-producing lining covers and protects the respiratory system, the organs and tissues involved in breathing. When a person has bronchitis, it may be harder for air to pass in and out of the lungs than it normally would, the tissues become irritated and more mucus is produced. The most common symptom of bronchitis is a cough.
When you breathe in (inhale), small, bristly hairs near the openings of your nostrils filter out dust, pollen, and other airborne particles. Bits that slip through become attached to the mucus membrane, which has tiny, hair-like structures called cilia on its surface. But sometimes germs get through the cilia and other defense systems in the respiratory tract and can cause illness.
Bronchitis can be acute or chronic. An acute medical condition comes on quickly and can cause severe symptoms, but it lasts only a short time (no longer than a few weeks). Acute bronchitis is most often caused by one of a number of viruses that can infect the respiratory tract and attack the bronchial tubes. Infection by certain bacteria can also cause acute bronchitis. Most people have acute bronchitis at some point in their lives.
Chronic bronchitis, on the other hand, can be mild to severe and is longer lasting — from several months to years. With chronic bronchitis, the bronchial tubes continue to be inflamed (red and swollen), irritated, and produce excessive mucus over time. The most common cause of chronic bronchitis is smoking.
People who have chronic bronchitis are more susceptible to bacterial infections of the airway and lungs, like pneumonia. (In some people with chronic bronchitis, the airway becomes permanently infected with bacteria.) Pneumonia is more common among smokers and people who are exposed to secondhand smoke.

Symptoms

For the first few days, the signs and symptoms of bronchiolitis are similar to those of a common cold:

• Runny nose
• Stuffy nose
• Slight fever (not always present)

After this, there may up to one week of:

• Wheezing — breathing seems more difficult or noisy when breathing out
• Rapid or difficult breathing
• Rapid heartbeat

In otherwise healthy infants, the infection generally goes away by itself in one to two weeks. If your child was born prematurely or has underlying health problems, such as a heart or lung condition or a weakened immune system, the infection may be more severe and your child may need to be hospitalized.
Severe bronchiolitis may cause marked difficulty breathing or bluish-looking skin (cyanosis) — a sign of inadequate oxygen.

Causes:

Acute bronchitis is usually caused by viruses, and it may occur together with or following a cold or other respiratory infection. Germs such as viruses can be spread from person to person by coughing. They can also be spread if you touch your mouth, nose, or eyes after coming into contact with respiratory fluids from an infected person.
Smoking (even for a brief time) and being around tobacco smoke, chemical fumes, and other air pollutants for long periods of time puts a person at risk for developing chronic bronchitis.
Some people who seem to have repeated bouts of bronchitis — with coughing, wheezing, and shortness of breath — may actually have asthma

Diagnosis

 

The doctor will likely listen to your child's lungs with a stethoscope to check for wheezing and prolonged breathing out (exhaling). These may indicate obstructed airflow in the bronchioles. The doctor may consider specific risk factors for bronchiolitis as well.
Sometimes other tests are recommended, including:

• Chest X-ray. In severe or uncertain cases, your doctor may request that a chest X-ray be taken to visually check for any signs of pneumonia. Your doctor may also check for the presence of a foreign object, such as a peanut or small piece of plastic, that your baby or toddler may have inhaled.
• Mucus sample test. In addition, your doctor may collect a sample of mucus from your child — using a nasal pharyngeal swab or a suction catheter that's gently inserted into the nose — to test for the virus that may be causing the bronchiolitis.
• Blood tests. Occasionally, blood tests might be used to check your child's white blood cell count. An increase in white blood cells is usually a sign that your body is fighting an infection. A blood test can also determine whether the level of oxygen has decreased in your child's bloodstream. An alternative test for oxygen levels is an oximeter that fits over the finger. Oxygen is necessary to the functioning of the body's organs, including the brain.

Your doctor may also ask you about signs of dehydration, especially if your child has been refusing to drink or eat or has been vomiting. Signs of dehydration include sunken eyes, dry mouth and skin, sluggishness, and little or no urinary output.

Treatments and Pharmacology

You can treat most cases of bronchiolitis at home with self-care steps. Because viruses cause bronchiolitis, antibiotics — which are used to treat infections caused by bacteria — aren't effective against it. If your child has an associated bacterial infection, such as pneumonia, your doctor may prescribe antibiotics for that.
In more-severe cases, doctors may prescribe inhaled antiviral drugs, such as ribavirin (Rebetol). However, studies haven't found this drug to be consistently effective.
If your child has complications from bronchiolitis, a stay at the hospital may be necessary. At the hospital, your child will likely receive humidified oxygen to maintain sufficient oxygen in the blood, and perhaps fluids through a vein (intravenously) to prevent dehydration.

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