LAB 17
RESPIRATORY LUNG VOLUMES
Objective: To measure and learn the various lung volumes and to understand how they can be
used to determine respiratory function.
A. Measurement of Individual Lung Volumes
Lung volumes vary with age, sex, size and respiratory health. Keep this in mind as measure lung volumes.
Obtain a dry spirometer and use it to determine the following:
1.
First, measure your vital capacity. Inhale and exhale forcibly several times to warm up. Finally, inhale as
much as you can and then exhale as much as you can into the spirometer. Be sure the spirometer is set at zero
before you begin each time. Take the reading. Repeat this procedure two more times.
a.
Calculate your average vital capacity by adding up all three readings and dividing by three. Enter your
average vital capacity into your table.
Vital Capacity 1
Vital Capacity 2
Vital Capacity 3
TOTAL
Avg. Vital Capacity
(Total/3)
2.
Compare your vital capacity with the expected value for a person your age and size given in the vital capacity
table. Enter the expected value into Table 1.
3.
Calculate your expected VC below. Show your calculations below and enter the % in Table 1.
% Expected VC 
4.
Your value
Expected value
 100
Determine your tidal volume (TV) by breathing normally and exhaling into the zeroed spirometer. This
should be a normal exhalation, not forced. Repeat this three times, each time after setting the spirometer back
to zero. Calculate your average TV and enter it into Table 1 (TV is usually about 10% of your vital capacity).
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Tidal Volume 1
Tidal Volume 2
Tidal Volume 3
TOTAL
Avg. Tidal Volume
(Total/3)
5.
Determine your expiratory reserve volume (ERV). Do this by exhaling normally (not into the spirometer)
then, forcefully exhale as much as you can into the spirometer. Again, be sure the spirometer is set at zero
before you begin. Record the reading in Table 1 (ERV is usually about 25% of VC).
6.
Calculate your inspiratory reserve volume (IRV) by plugging the known values into the equation below.
Show your calculations below and enter the number in Table 1 (IRV is usually about 65% of VC).
Vital Capacity = TV + ERV + IRV
7.
Calculate your minute respiratory volume. Show your calculations below and enter the value in Table 1.
Respiratory rate (breaths/min)
Minute Respiratory Volume = TV  Respiratory Rate
8.
Calculate the dead space. Show your calculations below and enter the number in Table 1.
Dead Space = TV x 30%
9.
The minute respiratory volume does not take into account the volume of air wasted in the dead space. To get a
more accurate measurement of respiratory efficiency, calculate the alveolar ventilation rate (AVR) and enter
the number in Table 1.
AVR = (TV - Dead Space)  Respiratory Rate
10. Residual volume (RV) is an amount of air that remains in the lungs even after a forceful expiration. This air
helps to keep the alveoli open and prevent lung collapse. Normally it is around 1200 mL. in males and 1100 mL
in females. Keep this in mind as you calculate total lung capacity below and answer the following questions.
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11. Total lung capacity (TLC) is the sum of all lung volumes (normally around 6000 mL in males). Calculate your
TLC and enter the number in Table 1.
a.
Use your text to write a formula to determine your total lung capacity. Write the formula, show the
calculations and your lung capacity as calculated below.
TABLE 1
FORMULA
Average Vital Capacity
Expected Vital Capacity (Table 2)
% Expected VC
Average Tidal Volume
Expiratory Reserve Volume (ERV)
Inspiratory Reserve Volume (IRV)
Minute Respiratory Volume (MRV)
Dead Space
Alveolar Ventilation Rate (AVR)
Total Lung Capacity (TLC)
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DATA
TABLE 2: Normal Vital Capacity of Adults* (in cubic cm)
Age in Years
Height
(inches)
20
30
40
50
60
70
60
3885
3665
3445
3225
3005
2785
62
4154
3925
3705
3485
3265
3045
64
4410
4190
3970
3750
3530
3310
66
4675
4455
4235
4015
3795
3575
68
4940
4720
4500
4280
4060
3840
70
5206
4986
4766
4546
4326
4106
72
5471
5251
5031
4811
4591
4371
74
5736
5516
5516
5076
4856
4636
58
2989
2809
2629
2449
2269
2089
60
3198
3018
2838
2658
2478
2298
62
3403
3223
3043
2863
2683
2503
64
3612
3432
3252
3072
2892
2710
66
3822
3642
3462
3282
3102
2922
68
4031
3851
3671
3491
3311
3131
70
4270
4090
3910
3730
3550
3370
72
4449
4269
4089
3909
3729
3549
Males
Females
QUESTIONS
1.
What is vital capacity?
2.
What is the significance of vital capacity?
3.
What is the inspiratory reserve volume?
4.
What is the expiratory reserve volume?
5.
What is tidal air?
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6.
What volume of air is important in the Heimlich maneuver?
7.
What physical principle is demonstrated when performing the Heimlich maneuver? (Review Boyle’s Law)
8.
What is the difference between alveolar ventilation and minute respiratory volume?
9.
What is dead space?
B. OXYGEN-HEMOGLOBIN DISSOCIATION CURVE
QUESTIONS
1.
What is being measured on the x-axis? _________________________________________
2.
What is being measured on the y-axis? _________________________________________
3.
Based on questions 1 and 2, what does the graph show?
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4.
What is the significance of a PO2 of 100 mm Hg?
5.
What is the significance of a PO2 of 40 mm Hg?
6.
At a PO2 of 100 mm Hg. what percentage of the total hemoglobin is saturated with O2________________ ?
7.
At a PO2 of 40 mm Hg. what percentage of the total hemoglobin is saturated with O 2________________ ?
8.
What does the difference between the percentages in questions 6 and 7 represent?
9.
What does it mean to shift the curve to the right and what is the result of doing so?
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