Biology 12
Name: __________________________
Lung Capacities
Spirometry is the diagnostic technique used to measure respiratory volumes. In this exercise, we
will compare predicted vital capacities with measured vital capacities.
Vital capacity (VC) is a reliable diagnostic indicator of one’s pulmonary stratus. To maintain
normal homeostasis, a person’s vital capacity should be at least 80% of the predicted value
(based upon gender, height, and age). Healthy individuals that exercise regularly may have vital
capacities near or even greater than their predicted value. Individuals that smoke, have asthma
or some COPD will have reduced vital capacities.
Predicting Vital Capacity
Use the following equations to predict you and your lab partners’ vital capacity:
Where:
Males:
VC = 0.052(H) – 0.022(A) – 3.6
Females:
VC = 0.041(H) – 0.018(A) – 2.69
VC = vital capacity in liters (L)
H = height in centimeters (cm)
A = age in years (yrs)
Determine your predicted VC using the proper formula and record this information in Table 1.
Measuring Vital Capacity
In this portion of the lab, we will be measuring VC using a simple, handheld spirometer. Follow
the instructions carefully and record your data in Table 1.
Before you begin, think about the relationship between actual and predicted vital capacities with
regard to one’s overall health and fitness. Form a hypothesis about your vital capacity by
selecting one of the following choices:
-
My actual VC will be less than 80% of my predicted VC
My actual VC will be between 80% and 100% of my predicted VC
My actual VC will be greater than 100% of my predicted VC
Hypothesis:
Rationale:
Procedure:
1. Obtain a handheld spirometer and disposable mouthpiece.
2. Set the spirometer dial to the zero mark before each trial.
3. While standing, breathe in and out normally for two to three times, and then exhale as
much as you can. Then, inhale as much as you possible can. It is important that you strain
to inhale as much air as physically possible. Then, quickly insert the spirometer with
mouthpiece, and exhale as forcibly as you can for as long as you can. Record your results
in Table 1 and repeat the exercise two more times.
4. Determine your actual VC expressed as a percent of your predicted.
Table 1. Measured and Predicted Vital Capacities
Subject
Trial 1 Trial 2 Trial 3
Average
VC
Predicted
VC
% Pre VC
Avg VC x 100
Pre VC
Analysis:
1. Did your results agree or disagree with your hypothesis? Why or why not?
2. If your actual values differ from your predicted values, what are some possible explanations for this?
3. How were the results for your lab partners?
4. Explain the following terms & how they relate to one another: tidal volume, inspiratory reserve
volume, expiratory reserve volume, and vital capacity.
Conclusion: Please include a conclusion in your formal lab write-up.