To begin the lesson, find out if any students in the class have asthma. Ask them what it feels like to have an asthma attack. To give students an idea, tell them to do the following: Pinch your nose closed, then breathe in and out through a straw. How hard is it to get fresh air into your lungs? How about getting the stale air out? Try to breathe fast, like you do when you are exercising. What does it feel like to have your body struggling for fresh air? How do you think your life would be different if you always had to worry that an asthma attack could happen, sometimes with little warning?

About 12 million Americans have asthma, which means someone you know probably has the disease. Even though it is so common, doctors don't know what causes asthma. They do know it isn't contagious. Asthma usually strikes during childhood. Half the children who get asthma outgrow it by adolescence. The other half spend their lives using medications and avoiding things that trigger attacks.

An attack happens when something irritates an asthma sufferer's respiratory system, triggering a series of events that make it difficult for the sophisticated structures within the lungs to get oxygen into the bloodstream. An asthma attack begins by striking the bronchi, the two large tubes that connect the windpipe to the lungs, and the bronchioles, the many little tubes that carry air from the bronchi deep into the lungs. In normal lungs, air from the bronchi moves into tiny air sacs called alveoli. Oxygen moves from these sacs into the bloodstream through tiny blood vessels called capillaries. At the same time, carbon dioxide is removed from the blood and exhaled from the body.

An asthma attack causes the muscles surrounding the lungs' airways to tighten. The airways can also become inflamed and swollen, making breathing much more difficult. Finally, the lungs increase production of mucus that clogs the airways even more. Asthma victims often make wheezing sounds and cough as they struggle to breathe and clear out the excess mucus. For someone with asthma, breathing out, or exhaling, is as hard as breathing in.

Scientists don't think asthma is inherited, but they suspect genes that make it easier for allergies and other environmental irritations to develop into asthma are passed on from parents to children. If neither parent has asthma, you have a 10 percent chance of developing it. If one parent has asthma, your odds increase to 25 percent. If they both have it, you have a 50 percent chance of developing the disease.

Many things bring on asthma attacks and these triggers vary from person to person. Cold winter air, cleaning solvents, dust, spicy food, aspirin, and cigarette smoke can all be triggers. Exercise and strong emotions also can cause attacks. So can viral and bacterial infections. With so many triggers, how can people with asthma live normal, active lives? Most do by inhaling medications that dilate, or open, constricted airways and stop inflammation. They also learn what their specific triggers are and try to avoid them. A cure isn't on the horizon, but people with asthma can control the disease and turn it into an inconvenience, not a barrier to a full life.

1. What other diseases affect the lungs and make it hard to breathe?

2. Would you tell your friends if you had asthma or some other disease that occasionally affected your ability to do things with them? Why?

In this activity you will create a simple model of the respiratory system. Not only will you measure the effect of narrowed airway channels, you will experience it as well.

Materials

• notebook, pen, and ruler
• construction paper, scissors, and tape
• balloons-large and round, that blow up to about 25 cm (10") in diameter
• plastic drinking straws .6 cm (1/4") in diameter, cut to 15 cm (6") lengths
• rubber bands 2.5-5 cm (1"-2") in length
• stopwatch or watch with sweep second hand
• honey dispensed from a plastic squeeze bottle with funneled spout

1. Divide into teams of four. Each team should use an inch-wide strip of construction paper and tape to make a ring 25 cm (10") in diameter. Each team member will need three balloons. Two of the balloons will be modified by inserting a 15 cm (6") length of drinking straw about 2.5 cm (1") into the opening and securing it with a small rubber band. (About eight twists will make the connection airtight and still not crimp the plastic straw.)

2. Each team member takes a turn at blowing up a plain balloon. Inflate the balloon until it just fills the paper ring, which is held by another team member. The third team member measures the time needed to inflate the balloon to the nearest second, while the fourth team member records the data. When inflation is complete, pinch the balloon shut. Reset the watch, then release the air from the balloon. Record the time it takes for the balloon to deflate completely.

3. When each team member has performed the trial with a plain balloon, repeat the entire process with one of the modified balloons. Record the times needed to inflate the balloon to 25 cm and to deflate it completely.

4. When this trial is finished, each team member takes the remaining modified balloon and squirts about 2 teaspoons of honey into the balloon through the straw. Gently squeeze the balloon so that the entire length of the straw is filled with honey. Inflate the balloon to 25 cm as before. Record the inflation and deflation times.

5. Calculate the average inflation and deflation times for the three trials performed by your team. Compare the results with those from the other teams.

Questions

1. In our model, the three balloons represent different conditions in the human respiratory system. What are they?

2. How did narrowing the passageway and adding a thick, sticky substance affect your ability to blow up the balloon?

3. How do medicines treat an asthma attack?

Ask a local doctor or school nurse to explain to your class what asthma is and demonstrate the inhalers asthma sufferers use to take their medicine. The doctor might also be able to let you try a peak-flow meter, a simple device asthmatics use to measure how well their lungs are working. If any students in your class have asthma, they can, if they want to, work with the doctor in the demonstration.

Do you suffer from allergies? Many people who don't have asthma are allergic to grass, different types of pollen, and even cat or dog hair. Go through magazines and cut out pictures of all of the things that cause you to sneeze, itch, or break out in a rash or that make it harder for you to breathe. Paste them in a notebook and compare your allergy triggers with those of your classmates. If these things caused more serious problems, like a full-blown asthma attack, how would you avoid them? Would you need to change your daily routine?