Lung Capacity Lab
The human lung is made up of elastic tissue and breathing occurs due to the contraction and
relaxation of the intercostal muscles and the diaphragm. During inhalation, the diaphragm and
intercostals muscles tighten. This drops the pressure in the lungs and allows air to enter. During
exhalation, respiratory muscles relax and air leaves the lungs as the pressure returns to normal.
There are various measurements which can be taken to obtain an understanding of how the lungs
work. These measurements may be taken with a piece of equipment called a spirometer. During
normal breathing, the average amount of air which is taken in and exhaled is called the tidal volume.
The maximum amount of air you can inhale and exhale in one breath is called the vital capacity.
However, even after as much air as possible is exhaled, there is still a small volume of air left in the
lungs. This is called the residual volume. The expiratory reserve is the volume of air you can breathe
out after normal inhalation and exhalation. The average values for male and female adults are listed
in the table below. The lung capacity values are related to several factors which include height,
gender, and fitness level.
Table 1. Average adult lung volumes measured with a spirometer. Volumes are in cm3 which
equals ml.
Male
Female
Vital Capacity
5000
4000
Expiratory Reserve
1200
1000
Tidal Volume
525
475
Procedure
Part I Breathing Rate
1. Breathe normally.
2. Have your lab partner record the number of times you inhaled in one minute.
3. Record this number here: __________________ breaths/minute.
Part II Vital Capacity
1. Cut the end off of the thumb of a rubber glove and fit it over the tube of a spirometer.
2. Inhale as much as possible and exhale all the air you can into the spirometer. After you have
exhaled as much as possible, read the scale on the side of the spirometer. This number shows your
vital capacity in Liters.
3. Record this number under the appropriate heading in Table 3.
4. Repeat this 2 more times.
5. Keep the rubber glove for part III and IV.
Part III Expiratory Reserve
1. Breathe normally.
2. After you exhale normally, force all of the remaining air in your lungs into the spirometer.
3. Record this number under the appropriate heading in Table 3.
4. Repeat this 2 more times.
Part IV Tidal Volume
1. You should now be fully aware of your normal breathing. Continue to breathe normally.
2. After inhaling a regular amount of air, exhale the amount of air you normally do into the
spirometer. Do NOT force more air out than you think is normal.
3. Record this number under the appropriate heading in Table 3.
4. Repeat this 2 more times
Part V Calculation of Expected Vital Capacity
1. Record your height in centimeters in Table 3. Multiply your height in inches by 2.54 to get your
height in centimeters.
2. Fill in your factor in Table 3 with the appropriate factor listed below.
3. Calculate your expected vital capacity by multiplying height by the factor you get in table 2 using
the following formula.
Height (cm) x Factor from table 2 = Calculated Vital Capacity
Table 2. Factor values according to gender and fitness levels.
Females
Low fitness level Medium fitness level High fitness level
20
21
22
Males
Low fitness level
25
Medium fitness level
27
High fitness level
29
My Calculated Vital Capacity is:
Table 3: Lung Volume in Liters
Trial #
Vital Capacity
1
2
3
Average
Expiratory Reserve
Tidal Volume
Conclusion Questions
(you can use the power point print out I gave you Tuesday or the book.)
1. Describe the mechanism of inhalation and exhalation.
2. Why do you think there is a residual volume of air remaining in the lungs even after you force as much out as
possible?
3. Did your experimental volumes (Table 3) match those indicated in Table 1? Give several specific reason why
there may be an error.
4. How does your experimental vital capacity (Table 3) compare with the calculated one in part V? Give a specific
reason why there might be an error.
5. How much air would you inhale and exhale in 1 minute?
6. How would an asthma attack affect the tidal volume?
7. Explain the difference between ventilation, gas exchange, and cellular respiration.