Control
of Human Respiration
Control
of Human Respiration
The disease of asthma is becoming epidemic in urban areas. The Breathing Easy WebQuest introduces this respiratory disorder's history and treatment. The following investigations will help complete your understanding of asthma by explaining the operation of your respiratory system and the absorption of O2 and release of CO2.
Your respiratory system allows you to obtain oxygen, eliminate carbon dioxide, and regulate the blood's pH level. The process of taking in air is known as inspiration, while the process of blowing out air is called expiration. A respiratory cycle consists of one inspiration and one expiration. The rate at which your body performs a respiratory cycle is dependent upon the levels of oxygen and carbon dioxide in your blood.
You will monitor the respiratory patterns of one member of your group under different conditions. A respiration belt will be strapped around the test subject and connected to a computer-interfaced Gas Pressure Sensor. Each respiratory cycle will be recorded by the computer, allowing you to calculate a respiratory rate for comparison at different conditions.
OBJECTIVES
In this experiment, you will
- use a computer to monitor the respiratory rate of an individual.
- evaluate the effect of holding of breath on the respiratory cycle.
- evaluate the effect of rebreathing of air on the respiratory cycle.
Figure 1
MATERIALS
Power Macintosh or Windows PC
Vernier Respiration Monitor Belt
Vernier computer interface
plastic produce bag 30 X 40 cm (12" X 16")
Logger Pro
small paper grocery bag
Vernier Gas Pressure Sensor
PROCEDURE
Figure 2
1. Prepare the computer for data collection by opening the Experiment 26 folder from the Biology with Computers folder of Logger Pro. Then open the experiment file that matches the probe you are using. There are two graphs displayed and two Meter windows. The top graph's vertical axis has pressure scaled from 96 to 110 kPa. The horizontal axis has time scaled from 0 to 180 seconds. The data rate is set to take five samples per second. The Meter window to the right displays live pressure readings from the sensor. The lower graph's vertical axis has respiration rate scaled from 0 to 20 breaths/minute. The horizontal axis has time scaled from 0 to 180 seconds. The Meter window to the right displays the calculated respiration rate when data is being collected.
2. If your Gas Pressure Sensor has a blue plastic valve on it, place the valve in the position shown in Figure 2.
3. Select one member of the group as the test subject. Wrap the Respiration Monitor Belt snugly around the test subject's chest. Press the Velcro strips together at the back. Position the belt on the test subject so that the belt's air bladder is resting over the base of the rib cage and in alignment with the elbows as shown in Figure 3.
Figure 3
4. Attach the Respiration Monitor Belt to the Gas Pressure Sensor. There are two rubber tubes connected to the bladder. One tube has a white Luer-lock connector at the end and the other tube has a bulb pump attached. Connect the Luer-lock connector to the stem on the Gas Pressure Sensor with a gentle half turn.
5. Have the test subject sit upright in a chair. Close the shut-off screw of the bulb pump by turning it clockwise as far as it will go. Pump air into the bladder by squeezing on the bulb pump. Fill the bladder as full as possible without being uncomfortable for the test subject.
6. The pressure reading displayed in the Meter window should increase about 6 kPa above the initial pressure reading (e.g., at sea level, the pressure would increase from about 100 to 106 kPa). At this pressure, the belt and bladder should press firmly against the test subject's diaphragm. Pressures will vary, depending upon how tightly the belt was initially wrapped around the test subject.
7. As the test subject breathes in and out normally, the displayed pressure alternately increases and decreases over a range of about 2 &endash; 3 kPa. If the range is less than 1 kPa, it may be necessary to pump more air into the bladder. Note: If you still do not have an adequate range, you may need to tighten the belt.
8. Instruct the test subject to breathe normally. Start collecting data by clicking . When data has been collected for 60 seconds, have the test subject hold his or her breath for 30 to 45 seconds. The test subject should breathe normally for the remainder of the data collection once breath has been released.
9. Examine the respiration rates recorded in the bottom graph by clicking the Examine button, . As you move the mouse pointer from point to point on the graph the data values are displayed in the examine window. Determine the respiration rate before and after the test subject's breath was held and record the values in Table 1.
10. Prepare the computer for data collection by opening the Experiment 26B folder from the Biology with Computers folder of Logger Pro. Then open the experiment file that matches the probe you are using. The vertical axis has pressure scaled from 98 to 112 kPa. The horizontal axis has time scaled from 0 to 300 seconds. The data rate is set to take five samples per second. The Meter window to the right displays live pressure readings from the sensor.
11. Place a small paper bag into a plastic produce bag. Have the test subject cover his or her mouth with the bags, tight enough to create an air-tight seal. The test subject should breathe normally into the bags throughout the course of the data collection process.
12. Click to begin data collection. Again, the test subject should be sitting and facing away from the computer screen. Collect respiration data for the full 300 seconds while breathing into the sack. Important: Anyone prone to dizziness or nausea should not be tested in this section of the experiment. If the test subject experiences dizziness, nausea, or a headache during data collection, testing should be stopped immediately.
13. Once you have finished collecting data in Step 12, calculate the maximum height of the respiration waveforms for the intervals of 0 to 30 seconds, 120 to 150 seconds, and 240 to 270 seconds:
a. Move the mouse pointer to the beginning of the section you are examining. Hold down the mouse button. Drag the pointer to the end of the section and release the mouse button.b. Click the Statistics button, to determine the statistics for the selected data.
c. Subtract the minimum pressure value from the maximum value (in kPa).
d. Record this value for each section as the wave amplitude in Table 2.
Table 1
1. Did the respiratory rate of the test subject change after holding his or her breath? If so, describe how it changed.2. What is different about the size (amplitude) or shape (frequency) of the respiratory waveforms following the release of the test subject's breath? Explain.
3. What would be the significance of an increase in the amplitude and frequency of the waveform while the test subject was breathing into the bag?
4. How did the respiratory waveforms change while the test subject was breathing into the bag? How would you interpret this result?
5. Explain how you think carbon dioxide affects your breathing.
The process of breathing accomplishes two important tasks for the body. During inhalation, oxygen-rich air is brought into your lungs. During exhalation, air depleted in oxygen and rich in carbon dioxide is forced out. Oxygen is then transported to the cells where it is used in the process of respiration, yielding carbon dioxide as a product.
6 CO2 + 6 H2O + energyGas exchange takes place in the lungs at the membrane between the alveoli and the pulmonary capillaries. It is here that oxygen diffuses into the bloodstream and carbon dioxide diffuses out. Under normal circumstances, there is an equilibrium between the oxygen and carbon dioxide levels in the blood. Several mechanisms are involved in maintaining this balance. One such mechanism involves chemoreceptors. These specialized cells respond to changes in carbon dioxide, oxygen and H+ concentrations and influence the body's ventilation patterns to maintain the proper balance of blood gases.
In this experiment, you will determine what factors affect how long you can hold your breath. You will be tested under two different conditions. The first condition is normal breathing. The second condition is immediately following hyperventilation. Hyperventilation is when your breathing rate is greater than what is necessary for proper exchange of oxygen and carbon dioxide. This will be achieved by a period of rapid breathing prior to holding your breath.
OBJECTIVES
Figure 1
MATERIALS
ring stand
Vernier computer interface
test tube clamp
Logger Pro
bread bag
Vernier O2 Gas Sensor
PROCEDURE
1. Secure the O2 Gas Sensor using a test tube clamp and ringstand as shown in Figure 1. The plastic bread bag should already be taped to the sensor.
2. Connect the O2 Gas Sensor to the Vernier computer interface.
3. Prepare the computer for data collection by opening the file in the Experiment 30 folder of Biology with Computers. The vertical axis has Oxygen concentration scaled from 12 to 22%. The horizontal axis has time scaled from 0 to 120 seconds. The data rate is set to 1 sample/second.
4. When you begin collecting data, it is important that data collection begins at the same point the subject begins to hold his breath.
a. Have the subject take a deep breath and hold it. Immediately click to begin data collection. The subject should hold his breath as long as possible.b. When the subject can no longer hold his breath, he should blow his breath into the bread bag and twist the open end shut. This should result in the bread bag filled with the air the subject was holding in his lungs. Allow data collection to proceed for the full 120 seconds.
c. When data collection has finished, open the bread bag and pull it back over the sensor exposing the sensor to room air. Leave the bag in that position until you are prepared to collect data again.
d. Click the Examine button. The cursor will become a vertical line. As you move the mouse pointer across the screen, the oxygen and time values corresponding to its position will be displayed in the box at the upper-left corner of the graph. Scroll across the data to determine how long the subject held his breath. Record the time in Table 1. Determine the maximum and minimum oxygen concentrations and record them in Table 1. To remove the examine box, click the upper-right corner of the box.
5. Move your data to a stored run. To do this, choose Store Latest Run from the Data menu.
6. Collect data following mild hyperventilation.
a. Pull the bread bag back down off of the sensor in preparation for data collection.b. Have the subject take 10 quick deep breaths, forcefully blowing out all air after each breath. The subject should then take an 11th breath and hold it. Immediately click to begin data collection. The subject should hold his breath as long as possible.
c. When the subject can no longer hold his breath, he should blow his breath into the bread bag and twist the open end shut. This should result in the bread bag filled with the air the subject was holding in his lungs. Allow data collection to proceed for the full 120 seconds.
d. When data collection has finished, open the bread bag and pull it back over the sensor exposing the sensor to room air.
e. Click the Examine button. The cursor will become a vertical line. As you move the mouse pointer across the screen, the oxygen and time values corresponding to its position will be displayed in the box at the upper-left corner of the graph. Scroll across the data to determine how long the subject held his breath. Record the time in Table 1. Determine the maximum and minimum oxygen concentrations and record them in Table 1. To remove the examine box, click the upper-right corner of the box.
7. Both runs should now be displayed on the same graph. Use the displayed graph and the data in Table 1 to answer the questions below.
DATA
(%) (%) (%)
QUESTIONS
1. Did the oxygen concentration change as you expected? If not, explain how it was different.
2. Did the amount of time you held your breath change after hyperventilation (taking the 10 quick breaths)? If so, did the time increase or decrease? Explain.
3. After hyperventilation, was the resulting concentration of oxygen in your exhaled breath higher or lower than in the first attempt? How much did it change? What do you contribute this to?
4. On the first trial, what do you believe forced you to start breathing again?
5. On the second trial, what do you believe forced you to start breathing again?
6. Based on your answers to questions 4 and 5, does the concentration of oxygen or carbon dioxide have a greater influence on how long one can hold his breath?