Lab 10: Respiratory Physiology
OBJECTIVES
 Define: TV, IRV, ERV, VC, RV, FRC, anatomical dead space, TLC
 Explain the mechanics of inhaling and exhaling
 Describe the effects of variation in blood carbon dioxide levels on respiratory
rate and depth
 Know the formulas for determining TV, IRV, ERV, VC, pulmonary ventilation
 (PV), alveolar ventilation (AV) and FEV1/FVC%
 Define hypo- and hyperventilation
 Explain the procedure for determining FEV1 and FEV1/FVC%
 Obtain information about PO2 and % saturation from an oxygen-hemoglobin
dissociation curve
 Draw, label and obtain information from a spirogram
 Given data, calculate oxygen carrying capacity of blood
SAFETY:
1) Put used mouthpieces and bacterial filters in biohazard bag.
2) If at any time you feel faint stop what you are doing, sit down, and put your head
down.
BACKGROUND:
The lungs can move between approximately 500 and 3000 ml of air in a single
inspiration or expiration. The volume of gas that is moved between the atmosphere and
the lungs depends on existing physiological conditions. If more oxygen is needed or
more carbon dioxide must be removed, then respiratory rate (RR) and/or tidal volume
(TV) increase, and vice versa. The respiratory rate and depth are controlled by the
respiratory center in the medulla oblongata. The major factors that affect the output of
the respiratory center are blood PCO2, pH, and PO2.
Respiratory volumes can be measured in several ways: 1) the actual amount of air
inhaled or exhaled can be measured, 2) changes in chest circumference can be measured
during breathing, or 3) air flow can be measured during breathing. Measuring the actual
volume using a wet spirometer is the most accurate method. Exhaled air displaces a
chamber within the spirometer and the volume is read from a scale or dial. Less accurate
spirometers use displacement of a small plastic ball in a column, or the revolution of a
wheel to approximate air flow.
In this lab we will use an electronic transducer that converts air flow in a tube into
electrical signals that are recorded and measured on the computer. This method is only as
accurate as the transducer’s calibration and is affected by how the flow head and tubes
are handled during measurement. You will create a spirogram like the one in your
textbook and use it to obtain values for TV, VC, IRV, and ERV.
NOTE: Students who have, or have had, asthma, epilepsy or bronchial disorders should
not be used as subjects.
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PROCEDURES:
A. Pulmonary Volumes
Equipment: computer and Labscribe software/hardware
spirometer transducer and flow head
disposable bacterial filter
disposable mouthpiece
1. Open LabScribe. From Settings, choose Load, then ahk114. Then from Settings,
choose breathing-rest-exercise. Put a new bacterial filter onto the flowhead as
demonstrated, then put the mouthpiece onto the filter.
NOTE: Always keep the plastic tubes that come out of the spirometer flow head in an
upright position. This prevents condensation of moisture in the tubes.
2. Have the subject practice breathing normally through the spirometer. The mouthpiece
opening should be inside the subject’s mouth—this prevents turbulent flow. When
she/he is comfortable with it, she/he will place the flowhead on the table for zero
calibration.
3. While the flowhead is sitting on the table, press the start button in LabScribe and wait
until the spirometer is calibrated (wait for 5 seconds after you press start). Watch for the
line to go down, then back up to the center of the window. If you don’t do this step, you
won’t be able to collect any data.
4. Have the subject pick up the flow head and breathe normally, inhaling and exhaling
through the spirometer. Don’t let them watch the screen. Type “resting” in the mark
window and press Enter. Click Autoscale for the channel 3 (top) window. Have the
subject record about 6 normal breaths, then without stopping, ask the subject to inhale as
deeply as possible, then exhale as deeply as possible, then immediately return to normal
breathing. The subject doesn’t have to inhale or exhale rapidly for this exercise, just
maximally.
errors:
1) If a vertical line appears on the screen during this recording it must be
repeated. Stop recording after about 6 normal breaths following the VC. See
diagram on board.
2) If the recording drifts up, stop recording (click Stop). Put the flow head down
on the table and recalibrate (Click Start and wait for the calibration signal on the
screen. Pick up the flow head and start breathing again.
5. Have the subject exercise until winded on the step platform. About 10 seconds before
she/he stops exercising, make sure the flow head is on the table, click the start button and
allow 5 seconds for zero calibration. Type “exercise” in the mark window and press
2
Enter. Then have the subject sit and immediately start breathing through the spirometer.
Record TV and VC as described in step 4 above.
6. The subject should remove her/his bacterial filter and mouthpiece from the spirometer
and discard them in the biohazard bag.
7. Save the file to the desktop.
8. Use the double cursor icon to insert cursors in the areas you are going to analyze.
Instructions on measuring will be covered during lab. Volumes are in the V2-V1 box in
liters (ignore any negative signs). Duration is measured from peak to peak and the value
is in the T2-T1 window in seconds.
resting TV
resting IRV
resting ERV
resting VC
duration of one resting tidal breath
exercise TV
exercise IRV
exercise ERV
exercise VC
duration of one post-exercise tidal breath
from the LabScribe data, show calculation for these values and include units:
resting RR
resting PV
resting AV (assume dead space of 125 mL for females, 150 mL for males)
exercise RR
exercise PV
exercise AV (assume dead space of 125 mL for females, 150 mL for males)
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Respiratory rate and depth are controlled by the respiratory centers in the brain stem
(pons and medulla oblongata). The inherent rate is set by a pacemaker and modified
according to the needs of the body. The main cues for altering respiratory rate and depth
are chemical ( blood carbon dioxide levels and pH) and mechanical (lung stretch). See
the textbook for details. Hyperventilation is defined as pulmonary volume above normal
and can be caused by an increased tidal volume or respiratory rate or both.
Hypoventilation is defined as pulmonary volume below normal and can be caused by a
decreased tidal volume or respiratory rate or both.
Equipment: paper bag
1. Record the subject’s resting respiratory rate and tidal volume by recording for one
minute (remember to zero calibrate the flow head first)
2. Have the subject hold the paper bag tightly over his/her mouth so that no air leaks in
or out and breathe into the bag for 2-3 minutes (stop if he/she feels faint)
3. Recalibrate, record for one minute, then stop
4. Allow the subject to return to normal RR and TV
5. Now have him/her breathe as deeply as possible for about 2 minutes (stop if
feels faint)
he/she
6. Recalibrate, record for one minute, then stop
7. Analyze the data to find TV and RR for each condition:
TV
RR
resting
after bag breathing
after hyperventilation
1. Complete these formulas:
a. VC = _____ + _____ + _____
b. based on a., TV = _____ – ( _____ + _____)
c. FRC = _____ + _____
d. TLC = _____ + _____
e. PV = _____ x _____
f. based on e., TV = _____  _____
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2. In order to inhale you have to (increase/decrease) the thoracic volume.
3. In order to exhale you have to (increase/decrease) the intra-alveolar pressure.
4. Hyperventilation is defined as a pulmonary ventilation that is
(less than/greater than/equal to) that needed to maintain normal blood CO2 levels.
5. What are the two things your body can do to increase PV?
6. Hyperventilation (increases/decreases/does not change) arterial PCO2.
Explain why?
7. Hypoventilation (increases/decreases/does not change) arterial PCO2.
Explain why?
8. Hypoventilation (increases/decreases/does not change) arterial PO2.
Explain why?
9. Hyperventilation (increases/decreases/does not change) arterial PO2.
Explain why?
10. Obtain this information from the diagrams in your textbook:
at a PO2 of:
normal % Hb saturation:
% saturation if curve is right-shifted due to
an increase in body temperature or decrease
in pH
40
60
80
100
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2. Draw a spirogram based on this data. Show one vital capacity (maximum
inhalation followed by maximum exhalation) and the resting tidal volumes. Label
both axes with variable and units. Label (on the graph): IRV, TV, ERV, RV and VC.
You will have to calculate some of the information you need from what is given below
but all of the information you need is in the chart. Use the spirogram in your textbook
as a model.
pulmonary ventilation
residual volume
respiratory rate
vital capacity
total lung capacity
functional residual capacity
5.4 L/min
0.9 L
12 / minute
3900 mL
4.8 L
1.9 L
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