1
Lung Capacity
Respiratory System
Name: _________________________
Date: ___________ Period: _____
Objective:
Demonstrate and explain lung capacity.
Key Terms:
Expiration Expiratory reserve volume Inspiration
Inspiratory reserve volume Residual volume Respiration
Respirometer Spirometer Tidal volume
Vital capacity
Background Information:
Inspiration, breathing in, and expiration, breathing out, occur because of a pressure gradient.
Clinically, the term respiration includes one inspiration plus one expiration.
The amount of air taken in or expelled during normal breathing is called the tidal volume.
When a very deep breath is taken, the volume of inhaled air is known as the inspiratory reserve
volume. When a normal breath is taken in and then forcibly expelled it is known as the expiratory
reserve volume. The vital capacity is the maximum amount of air that can be exhaled after taking the
deepest breath possible. Residual volume is the amount of air left in lungs even after maximal
expiration.
Human lung capacity can be measure in several ways. One way is by using a piece of
laboratory equipment called a respirometer or spirometer. A less accurate (but very sanitary) method
to measure lung capacity is by using a balloon.
Procedure A: VITAL CAPACITY
1. Blow up the balloon several times to stretch it before beginning to take measurements.
2. Take as deep a breath as possible: exhale as much air as possible into the balloon; pinch the
balloon closed to prevent air from escaping.
3. Measure and record the circumference of the balloon.
4. Repeat this procedure four more times; record each circumference.
5. Calculate and record the average.
Procedure B: EXPIRATORY RESERVE
1. Inhale and exhale normally.
2. During exhalation, exhale all the air left in your lungs into the balloon; pinch the balloon
closed to prevent air from escaping.
3. Measure and record the circumference of the balloon.
4. Repeat this procedure four more times; record each circumference.
5. Calculate and record the average.
Procedure C: TIDAL VOLUME
1. Take in a normal breath; exhale into the balloon only as much air as you would normally
exhale. Do not force the air.
2. Pinch the balloon closed to prevent air from escaping.
3. Measure and record the circumference of the balloon.
4. Repeat this procedure four more times; record each circumference.
5. Calculate and record the average.
