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SBI 3U
Ms. Girvan
Name: ___________________________
Date: ____________________
Lab Investigation – Measuring Lung Volume
Introduction:
Lung volume varies among individuals and depends on many factors, such as sex, body
size, physical fitness, and lifestyle behaviours such as smoking. One indicator of physical
fitness is the maximum amount of oxygen that the body uses during strenuous activity.
You can use an instrument called a spirometer to measure the amount of air that you
breathe during normal breathing or during forced inhalation and exhalation
The wet spirometer is a water filled reservoir used for determining various lung
volumes. The subject breathes through a flexible tube attached to a “bell” which floats
in the reservoir. When air is blown into the tube, the bell raises in the reservoir – the
amount of bell movement corresponds to the volume of gas inhaled or exhaled. A
calibrated scale attached to the
bell measures the volume of air exchanged.
During the experiment the subject should be seated with their back straight and their
eyes closed. Be careful not to change positions during the investigation and the subject
should not watch the experimenter or the spirometer during a trial. Normal values
cannot be determined if the subject is excited or has just completed some physical
activity. Block the nose by pinching; as well, always form a tight seal around the mouth
piece
You should become familiar with the scale of the instrument before you begin.
Pre-Lab Questions:
1. What medical purposes could be served by measuring respiratory volumes?
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2. What variables might affect the measurement of respiratory volumes in a single
individual? Does this investigation control for those variables?
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Safety Precautions:
It is very important for hygienic reasons to use a new mouthpiece for each student.
Write your name on it as soon as you have one and hang onto it until you are satisfied
that you have successfully completed the investigation.
Material and Apparatus:
Wet spirometer
Disposable Mouth Piece
Water
**The wet spirometer is designed to measure the volume of air that is forced into it. Do
not inhale through the mouthpiece of the spirometer at any time. **
Procedure:
 Part A – Measuring Tidal Volume (TV)
Tidal volume is the amount of air exhaled or inhaled during normal, quiet breathing.
1. The subject should sit by the spirometer, breathing quietly and normally for about
one minute before using the spirometer.
2. After inhaling a normal breath the student places the mouthpiece between the lips
and exhales in a normal, unforced way into the spirometer.
3. Record the volume in the table. Repeat the procedure three times; making sure that
the pointer is reset to zero before each reading.
4. Determine the average Tidal Volume of your three determinations.
 Part B – Measuring Expiratory Reserve Volume (ERV)
Expiratory reserve volume is the amount of air that can be forcibly breathed out after normal
expiration.
1. The students sits, breathing normally for a minute or so, then after a normal,
unforced exhalation puts the mouthpiece between the lips, and forcible exhales all
additional air possible.
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2. Again, record the results of 3 trials, resetting the spirometer pointer to zero after
each. Determine the average of the three trials.
 Part C – Measuring Inspiratory Reserve Volume (IRV)
Inspiratory reserve volume is the amount of air that can be inhaled after a normal, unforced
inhalation.
1. Inhale as deeply as you can, and then exhale normally into the spirometer. Do not
force the exhalation. Record this value as your inspiratory capacity.
2. To calculate your inspiratory reserve volume, subtract your tidal volume from your
inspiratory capacity. Record this value as your inspiratory reserve volume.
3. Again, record the results of 3 trials, resetting the spirometer pointer to zero after
each. Determine the average of the three trials.
 Part D – Measuring Vital Capacity (VC)
Vital Capacity is the maximum amount of air that can be forcible exhaled immediately following
a maximal inhalation.
1. The student, sitting, slowly and deeply breathes in and out for a while, and then
breathes in as deeply as possible, places the spirometer mouthpiece in position, and
exhales as forcibly as possible. Repeat three times and record the results in the table.
Observations:
LUNG
VOLUMES
TIDAL
VOLUME
EXPIRATORY
RESERVE
INSPIRATORY
CAPACITY
INSPIRATORY
RESERVE
TRIAL 1
mL
TRIAL 2
mL
TRIAL 3
mL
AVERAGE
mL
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VITAL
CAPACITY
Calculations:
Vital Capacity can also be determined by adding the previously measured lung volumes:
VC = IRV + ERV + TV
Total Lung Volume
The total lung volume is determined by adding the vital capacity and the residual volume.
Residual Volume (RV)
Residual Volume is the air within the lungs that remains after forcible exhalation. It cannot be
measured with the spirometer. For an average, healthy individual make the residual volume is
about 1200mL.
Complete the following calculations:
I. Vital Capacity (VC) = TV + IRV + ERV
=
=
II. Total Lung Volume = VC + Residual Volume
=
=
(note: use measured VC)
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Discussion:
Here are a number of topics to discuss:
1. Define any lung volume terms discussed in the lab.
2. Compare the spirometer results to the calculations and explain any differences.
3. Compare IRV to ERV values and explain why there is a difference between the two.
4. Discuss how lung volumes would differ between each of the following cases:
i. athlete vs. non-athlete
ii. smoker vs. non-smoker
iii. large vs. small person
It is necessary to show evidence of outside research in your lab report.
Outline of Formal Lab Report:
1. Abstract
2. Introduction
3. Materials/Apparatus
4. Procedure (refer to the lab handout)
5. Observations (lead in sentence, table filled in with reasonable numbers, title below
table)
6. Calculations (work and formula shown)
7. Error Analysis
8. Discussion
9. Conclusion
10. References (must be used properly in discussion and listed)
**A rubric will be provided to you that outlines the marking scheme. **