Computer
Oxygen and Aerobic Metabolism
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Oxygen plays a key role in aerobic cellular metabolism, facilitating the conversion of glucose,
protein, and lipids into usable energy. For every 6 molecules of oxygen used in the breakdown of
glucose, 6 molecules of carbon dioxide are produced, along with water and adenosine
triphosphate (ATP), according to the following equation:
C6H12O6 + 6O2 → 6CO2 + 6 H2O + energy (heat or ATP)
The average person uses 200–250 mL of O2 per minute at rest. This may increase to 2–3 L per
minute during heavy exercise and to twice that amount in highly trained athletes. The increase of
oxygen consumption is proportional to the amount of work performed up to a maximum level
which is dependent on conditioning. At the start of exercise, anaerobic metabolism is used
briefly, but this quickly changes to aerobic metabolism as blood flow to muscles increases.
As O2 is consumed and CO2 produced by muscle cells (and other cells), a pressure gradient is
created between the cells, the interstitial fluid, and the bloodstream. A marked lowering of O2 in
interstitial fluid as it is used up by cells leads to O2 diffusion from the bloodstream. While
dissolved O2 provides an immediate supply to replenish the interstitial fluid and cells, the
majority of O2 is carried on hemoglobin molecules. Oxyhemoglobin dissociates more readily as
the oxygen concentration is lowered (and CO2 concentration increased), rapidly replenishing the
supply of dissolved O2. CO2 diffuses from active cells (where it is produced in high
concentration) to the interstitial fluid and bloodstream, where it is transported to the lungs mainly
as bicarbonate. In the lungs, the opposite is true. O2 follows a pressure gradient from the alveoli
into the bloodstream, and CO2 from the bloodstream into the alveoli.
In this experiment, you will measure tidal volumes and oxygen concentrations of deeply inhaled
and exhaled air at rest and after exercise. You will use these measurements to calculate the
resulting differences in oxygen consumption.
Important: Do not attempt this experiment if you have pulmonary or musculoskeletal problems
that might be aggravated by exercise.
OBJECTIVES
In this experiment, you will

Obtain graphical representation of tidal volume and change in O2 concentration with
breathing at rest and after exercise.
 Calculate oxygen consumption at rest and after exercise.
 Correlate your findings with clinical situations.
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MATERIALS
LabQuest
Spirometer
O2 Sensor
Vernier CO2-O2 Tee
disposable bacterial filter
nose clip
4 cm (¾ in.) PVC pipe
PROCEDURE
Part I Oxygen utilization at rest
1. Assemble the apparatus (see Figure 1).
a. Make sure that the PVC pipes are inserted
into both ends of the CO2-O2 Tee.
b. Insert the O2 Gas Sensor into the vertical
opening of the CO2-O2 Tee. Identify the
side of the Spirometer head marked “Inlet”
and insert the CO2-O2 Tee (smaller diameter
end) into it.
c. Insert the bacterial filter (smaller diameter
side) into the larger opening end of the CO2O2 Tee. Caution: Do not puncture the filter
material inside the bacterial filter.
2. Press the silver power button on the front top left side of the LabQuest to turn it on. Connect
the Spirometer into Ch1 (on the top right side) on the labpro and the O2 sensor into CH2
using the white square plugs.
3. Hold the apparatus in one or both hands and brace your arm(s) against a solid surface, such
as a table To zero the spirometer use the stylus to tap ‘Sensors’ and then then tap ‘Zero’ from
the dropdown menu. Tap ‘CH 1: Spirometer’ to finish zeroing. Do not zero the O2 Sensor.
Note: The Spirometer must be held straight up and down during data collection (see
Figure 1).
4. Collect inhalation and exhalation data.
a. Put on the nose clip or use your free hand to hold
your nose shut.
b. Use the stylus to tap the green collect button on the
lower left of the screen to begin data collection.
c. Taking deep breaths begin data collection with an
inhalation and continue to breathe in and out. Each
respiratory cycle should last 4–6 s (2–3 s per
inhalation and 2–3 s per exhalation). Continue
breathing in this fashion for the duration of the
experiment. After 40 s tap collect again to stop data
collection.
Figure 2
5. Use the stylus to tap ‘Analyze’ at the top of the screen and then ‘Delta’ from the dropdown
menu. Tap ‘Graph 1’ to select the volume graph. Place the stylus on the second peak of the
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volume graph. Tap and drag down to the valley that follows it. Enter the y value displayed
in the lower left corner of the graph to the nearest 0.1 L as Breath 1 Pre-exercise Tidal
Volume in Table 1.
7. Repeat Step 5 for a total of 3 breaths, entering the y values for each breath in Table 1. Press
OK to return to the main graphs.
8. Tap ‘Analyze’ then “Delta’ then ‘Graph 2’ to look at the gas vs. time graph. Place the stylus
on the second peak of the graph. Tap and drag down to the valley that follows it. Enter the y
value displayed in the lower left corner of the graph to the nearest 0.01 % as Pre-exercise
∆O2 Concentration in Table 1.
9. Repeat Step 8 for a total of 3 breaths, entering the y values for each breath in Table 1. When
you are finished tap OK to exit Delta Analysis mode.
Part II Oxygen utilization during exercise
10. Begin running in place for 2 minutes, moving arms as well as legs.
11. At the end of two minutes, pick up the apparatus in one or both hands. Brace your arm(s)
against a solid surface, such as a table, and zero the spirometer again by tapping ‘Sensors’
then ‘Zero’ then ‘CH1 : Spirometer.’ Do not zero the O2 Sensor. Note: The Spirometer must
be held straight up and down during data collection (see Figure 1).
12. Collect inhalation and exhalation data.
a. Put on the nose clip or use your free hand to hold your nose.
b. Tap collect to begin data collection.
c. Taking deep breaths begin data collection with an inhalation and continue to breathe in
and out. Each respiratory cycle should last 4–6 s (2–3 s per inhalation and 2–3 s per
exhalation). Continue breathing in this fashion for the duration of the experiment. After 40
s tap collect again to end data collection.
VERY IMPORTANT: Discard the disposable bacterial filter into the biohazard bin
in the lab and replace with a fresh one between each student usage. Note: If you
are continuing this lab over 2 or 3 different lab periods, please store your filter in a
plastic bag with your name on it for reuse and place it into the bin provided on the
lab cart. Discard filter in Biohazard bin on final lab day.
14. Use the stylus to tap ‘Analyze’ at the top of the screen and then ‘Delta’ from the drop down
menu. Tap ‘Graph 1’ to select the volume vs. time graph. Place the stylus on the second peak
of the graph. Tap and drag down to the valley that follows it. Enter the y value displayed in
the lower left corner of the graph to the nearest 0.1 L as Breath 1 Post-exercise Tidal Volume
in Table 1.
15. Repeat Step 14 for a total of 3 breaths, entering the y values for each breath in Table 1.
When finished press OK to return to the home screen.
17. Use the stylus to tap ‘Analyze’ at the top of the screen and then ‘Delta’ from the drop down
menu. Tap ‘Graph 2’ to bring up the Oxygen Gas vs. Time graph. Place the stylus on the
second peak graph. Tap and drag down to the valley that follows it. Enter the y value
displayed in the lower left corner of the graph to the nearest 0.01% as Post-exercise ∆O2
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Concentration in Table 1.
18. Repeat Step 17 for a total of 3 breaths, entering the y values for each breath in Table 1.
19. Compute the average value for each of the parameters measured using a calculator and enter
those values in Table 1.
To save the data:
a. Insert a USB drive or SD card into the top of the LabQuest.
b.
On the home screen use the stylus to tap ‘File’ at the top of the screen and select
‘Export’ from the drop down menu.
c.
Tap on the picture of USB or SD to enter the devices’ files.
d.
Tap on ‘Untitled’ and use the on screen keyboard to change the name of your file.
e.
Tap OK to finish saving. This file is now saved as a .txt file and can later be
copied into excel.
When finished:
a) Shut down the LabQuest by holding down the silver power button. If you did not want to
save your data tap ‘Discard’ to complete the shutdown. Disconnect the spirometer and O2
sensor and return the LabQuest to its box on the cart.
b) Place all equipment besides the LabQuest into the ANP storage bins. Please use the
Velcro power chord tie wraps on all of the devices to roll up the chords before placing
them in the storage bins. Discard all used disposable filters and mouthpieces in the
Biohazard containers in the lab.
DATA
Table 1
Tidal volume (L)
Breath
Pre-exercise
Post-exercise
∆O2 Concentration (%)
Pre-exercise
Post-exercise
1
2
3
4
Average
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DATA ANALYSIS
1. Compare the tidal volumes of the 4 breaths you analyzed both at rest and post-exercise. Is it
important for this experiment that resting and post-exercise tidal volumes be similar?
2. Inhaled oxygen should have the same concentration at rest and post-exercise (approximately
21%), yet the peak oxygen concentration values in the post-exercise run never achieve this
value. What aspect of the experimental design accounts for this finding?
3. Use the average values for Tidal Volume and ∆O2 Concentration (%) from Table 1 to
calculate the average O2 consumed pre- and post-exercise per breath and over the combined 4
breaths:
∆O2 Concentration (%)  Tidal Volume (L) = O2 consumed per breath
O2 consumed per breath  4 breaths = O2 consumed over that time interval
4. CO2 was not measured. What would you expect the volume of exhaled CO2 to be in this
experiment at rest and after exercise?
EXTENSIONS
1. Oxygen consumption with exercise is directly proportional to the muscle mass being used.
Demonstrate this principle by performing this experiment exercising with your legs only
and/or with your arms only.
2. Perform this experiment after exercising for varying lengths of time (1 minute or 5 minutes).
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