Lung Function in Asthma


The airways of asthmatics are much more sensitive and reactive than the airways of people who do not have asthma. They tend to become irritated very easily. In a child who has asthma, the functions of the airways and the mucus glands become hyperactive. During an asthma episode, three events take place in the airways. Together, they cause the airways to get smaller. Therefore, it becomes more difficult to get air in and out of the lungs. If severe, the symptoms may lead to severe shortness of breath and low levels of oxygen in the blood.

First, the muscles around the airways tighten. This squeezes the airways partly closed. Second, the lining of the airway swells. This makes the walls of the airway take up more space and leaves less room for air to pass through. Third, the mucus glands in the airways work harder and produce extra mucus. This extra mucus blocks or plugs the airways. The airway swelling and mucus secretion are part of airway inflammation which causes irritation.

When the airways narrow, more work must go into breathing to push air through the lungs. This is an asthma episode. Wheezing is the sound caused by air being forced through narrowed air tubes and around the extra mucus. When someone has an asthma episode, they wheeze. The sticky mucus, which the airway glands make when asthma symptoms increase, is very irritating and often causes persistent coughing.

The struggle to breathe and coughing are a lot of extra work for the child. During an asthma episode, muscles not normally needed for quiet breathing may be needed to help move air in and out. A child may be seen using neck and shoulder muscles and the muscles attached to the ribs to help breathe during the episode. You will notice your child taking longer to get each breath out. This extra work causes symptoms such as sweating, fatigue, and irritability.