Measuring Lung Capacity, by John Cowens

Take a deep breath – your students are going to love these science activities about the lungs

The lungs are complex organs in the respiratory system. Their role is to take in oxygen and get rid of carbon dioxide. Air enters through the nose or mouth, past the epiglottis and into the trachea. As the gas moves down the trachea, it passes the vocal cords located in the larynx until it meets the bronchi. At this point, air passes into each lung and travels through a network of narrower bronchioles until it reaches the alveoli. Each alveoli has a mesh-like covering of small blood vessels called capillaries.

Just a second
Since the oxygen concentration is high at each alveoli, it diffuses across the alveolar membrane and into the pulmonary capillary. It's at this point the hemoglobin in red blood cells has carbon dioxide bonded to it with oxygen. However, as oxygen binds to hemoglobin, carbon dioxide is released. Since the level of carbon dioxide is high in the pulmonary capillary, it leaves the blood and passes the alveolar membrane into the air sac. The exchange of gases that occurs in a fraction of a second is amazing!

As the lungs exhale, carbon dioxide exits the alveoli and leaves oxygen-enriched blood that travels to the heart. It's imperative to keep oxygen concentration high and carbon dioxide low to maintain proper gas exchange in the lungs.

Inhale, exhale
The following activities demonstrate the concept of lung capacity. The relationship between height and vital capacity will also be investigated. These activities provide experience with fundamental principles of good scientific observation such as hypothesizing, experimenting, measuring, collecting, recording data and stating a conclusion.

Materials:

• graph paper
• pen
• balloons
• measuring tape
• red and blue markers

Procedures:

1. Make a graph that you'll use to mark your volunteers' results. On the left-hand side of a piece of paper, write "circumference in inches," and starting with 1" at the bottom, write numbers by 1/2" increments all the way until you reach 12".

   You can download a copy of this graph here. PDF 12KB

2. Along the bottom of your graph, write the names of your students, their height, weight and fitness level.

3. Find out your first student's fitness level by asking how many minutes he or she exercises each day. Rate their fitness level on a scale of 0 to 10, based on the following chart:

   If a person exercises:	He/she rates:
   1 to 2 hours, 5-7 days/week	10
   1 hour, 4-5 days/week	8
   30 min., 4-5 days/week	6
   30 min., 2-3 days/week	4
   30 min., 1 day/week	2
   Never	0

   Write each student's fitness rating on your graph next to his or her name, along with his or her weight and height.

4. Determine the reserve air capacity of the student by asking him or her to breathe out normally. Then, ask him or her to blow what air is left in his or her lungs into a round balloon. Students will quickly discover that new balloons can be more difficult to inflate than a "used" balloon. Allow students to inflate their new balloon 4-5 times before measuring and recording the circumference.

5. Measure the largest circumference of the balloon with a measuring tape. Using a blue marker, place a dot on your graph where the name and the number on the left meet.

6. Now find the student's vital capacity by asking him or her to take the deepest breath he or she can, then blow every bit of air into the balloon. Again, measure the balloon's largest circumference and record the number on your graph using a red marker. Compare your results.

Vital lung capacity
Students can work in groups to help measure and record their vital lung capacity (the amount of air that can be exhaled). Students should know that this amount excludes the three pints of air that remains in the lungs. Ask them to also measure their height and then form their own hypothesis about a possible correlation between height and vital capacity.

Materials:

• Measuring Vital Capacity graph download here. PDF 8KB
• Lung Volume Bags and mouthpieces.

Procedures:

1. Divide the students into small groups. Each student should have his or her own lung volume bag, mouthpiece and graph.

2. Have each group of students measure one another's height and record it on their graph.

3. Ask each group of students to measure their vital capacity twice, using the lung volume bag and record the information on their graph.

4. Students compare their vital capacity to how much air they actually exhale during normal breathing.

5. Inform students that we breathe about a half liter (1 pint) with every breath and we breathe from 10-14 times per minute.

John Cowens teaches sixth grade at Fleming Middle School in Grants Pass, OR.