Lesson Plan

How Big is a Breath? Lung Capacity

Objectives

You will measure your lung capacity in a hands-on activity involving different scientific process skills like observing, estimating and measuring.

Time Required

30 min. for preparation, 50-80 min. to conduct actual measurements, 50 min. to gather data and discuss results.

Materials

A large, clear plastic container (such as Rubbermaid) with 2-4 liters capacity; a Pyrex measuring cup with metric measurements; water; proximity to a sink; permanent markers; rubber balloons (two or three for each student)

Introduction

This lesson is designed to complement the Wildcat Sports Center activity on the Dig Deeper CD. Smoking affects the physical performance of athletes by reducing their overall lung capacity and ability to absorb oxygen. On the CD, students looked at lung capacity indirectly by counting the number of breaths taken in a minute. In this hands-on classroom activity, students can examine their own lung capacities through direct observation and measurement.

Background Information

Cartoon of lung The lungs take in air through the bronchial tubes, which branch off like a tree into smaller and smaller tubes. Each tube ends in an alveoli, which is like a small air balloon. The average person has over 6 million alveoli, 3 million in each lung. Altogether, they can take in anywhere between 4 to 6 liters of air per breath.

But there are many different ways to measure lung capacity, or the amount of air our lungs can take in. One way is to measure the amount of air we take in during a normal breath; this is called the tidal volume. There's also the amount of air we can take in with a really deep breath; this is called the vital capacity of our lungs. What we are going to measure is the average tidal volume of our lungs.

Preparation

Place the large plastic container on a level surface.
Using the Pyrex measuring cup, pour in 200 mL of water into the container, and mark the level of the water on the outside of the container with permanent marker.
Repeat the previous step until you have poured about 4 liters of water into the container.
Make sure each of the markings for the water level is labeled: 200 mL, 400 mL, etc. Mark shorter lines halfway between each of the existing marks, approximately indicating the 100 mL level.
Pour out all but 2 liters of water. (If you are not sure you have 2 liters, pour all of the water out and then refill it with 2 liters measured by the Pyrex cup.)

Activity

Create a table on the chalkboard with 2 columns: student's name, tidal volume in liters. Write every students' name into the first column, and leave the second column blank.
Pass out 2-3 rubber balloons to each student.
Using the background information, explain what tidal volume is. Have each student take five breaths, inhaling and exhaling at a normal rate. On the last exhale, have students exhale into their balloon. (If anyone messes up by giggling or letting the air out, she can just start over.) Tie up the balloons by knotting them at the ends (or use string if knotting becomes cumbersome), and then repeat with the remaining balloons.
As each student finishes their balloons, have the student write her name in permanent marker on each of the balloons.
Each student will then submerge her balloon into the large plastic container filled with water, trying to get as much of the balloon under water as possible without putting her hands underwater as well.
Note the level that the water rises to when the balloon is submerged. Subtract 2 liters (or 2000 mL) from this amount to determine the volume of the water displaced. This is the tidal volume contained in the balloon. Round the measurement to the nearest 100 mL.
When each student has submerged and measured all of her balloons, have her calculate the average tidal volume of all three balloons, and then write her result onto the board next to her name.

Questions for Discussion

What's the average tidal volume for the entire class? How much do the smallest and largest tidal volume differ from average?
Are there any explanations for why each student has a different tidal volume lung capacity? Think about factors such as weight, height, gender, frequency of exercise, etc.