Wellness Medical Care

“Normal” breathing means different things for different children. One child breathes quietly, while another makes noise with each breath. A child at rest takes slow, deep breaths, while a running child breathes quickly. Given the range of normal, it can be difficult to tell when breathing is abnormal.

You will hear several terms used to describe “abnormal breathing.” Labored breathing refers to rapid, often shallow breathing associated with increased effort to take each breath. Respiratory distress is an exaggerated form of labored breathing that is associated with not getting enough oxygen into the body.

Wheezing is a sound heard on exhalation, a high-pitched whistle. It may be associated with labored breathing or respira­tory distress, or it may not. The easiest way to understand why breathing may be labored to understand the path that air follows from the nose and mouth down to the lungs.

Air enters the airway through the nose or mouth and heads down the trachea, passing the vocal cords. It goes through the main stem bronchus into the right and left bronchi. It passes along an ever-narrowing channel of tubes, divided among the various bronchioles, eventually reaching the end of the lungs at grapelike sacks called alveoli.

There are some important general rules to know about the flow of air. First, air follows the path of least resistance. Therefore, if something is blocking one particular route, air will be less likely to flow in that direction and more likely to find an unobstructed path. Second, air is only 21 percent oxygen.

When doctors talk about “air exchange” and the importance of air, they are usually referring to oxygen. If you recognize that oxygen is a relatively small component of air, you will understand why giving extra oxygen — increasing the relative percent of oxygen being inhaled in air — can often help a child with labored breathing or respiratory distress.

The whole goal of breathing is to get oxygen into the body. The more difficult this goal is to accomplish, the harder a child will work to get it done.

The most common general cause of difficulty breathing is obstruction of the airway. What blocks the airway? Physical objects, such as accidentally swallowed toys, can do it. Mucus can block the airway, too. The mucus that complicates breathing is generally a byproduct of an infection.

Other infections can physi­cally block breathing by causing swelling within the airway. This swelling reduces the diameter of the airway, a form of obstruc­tion. And any process that causes inflammation of the airway, such as allergy or asthma, causes obstruction and difficulty breathing for the same reason.

Asthma is the most common cause of breathing difficulty among children in the United States. It is estimated that 9 million American children are asthmatic. This represents 12 percent of all children in this country, a sharp increase from the 8 percent in 1995.

Asthma is responsible for 4.6 million outpatient visits, more than 700,000 emergency room visits, and more than 200,000 hos­pitalizations among children each year.

Although asthma is typically equated with wheezing, this is not the right way to think about it. Asthma has three components: muscle hyperreactivity, mucus secretion, and inflammation. To have asthma, a child must have all three of these things going on in the lungs. In medicine, there is a saying: All that wheezes is not asthma.

Basically, when a child has asthma, this is what happens: The child is exposed to something that triggers her asthma — ciga­rette smoke, pollen, cat dander, even a virus. The irritant causes the muscles lining the medium-size airways to spasm, and the spasm causes the airway diameter to shrink.

Normally open air­ways become small — acting as if they are obstructed — and smaller airways present increased resistance to airflow. When this happens, breathing is difficult, but it is generally easier for the air o get into the lungs than it is for the air to leave. This phenome­non causes a classic wheeze on the exhale but not on the inhale.

Meanwhile, the irritant also stimulates cells lining the airway to produce mucus. This is part of the normal immune system response, but with the narrowed diameter of the airways, the mucus can cause more harm than good. Thick mucus congests the airways, narrowing their diameter even more and adding to their obstruction.

Finally, inflammation occurs in the alveolar, the smallest, most distant part of the lungs. The alveoli are the sites of air exchange, en these sacks are coated with inflammatory cells, it becomes ore difficult for oxygen to pass through them and into the bloodstream. Therefore, air exchange is reduced, and the effi­ciency of breathing is further reduced.

Because all three of these components contribute to the labored breathing of asthma, all three must be treated to resolve e problem. It is important to remember that just because a child wheezes, it does not necessarily mean that she has asthma. The converse is also true: not all children with asthma wheeze. In fact, there is a well-known variety of asthma called cough-variant asthma in which there is coughing rather than wheezing.

A child should not be called “asthmatic” after the first episode of wheezing, unless the episode was so severe that the child required hospitalization. Rather, the first episode of wheezing is usually called reactive airways disease (RAD). Typically, after three episodes of RAD, a child will earn the diagnosis of asthma.