Figure 1. A schematic diagram of the human respiratory system.

Introduction to Respiration In this experiment, you will investigate various aspects of normal breathing, hyperventilation, rebreathing the effect of changing airway resistance and ways in which to measure lung function. Background Cells in your body consume oxygen and produce carbon dioxide. These gases are exchanged between cells and blood through your lungs. Breathing movements pump air in and out of the lungs, where close contact between air and blood occurs, allowing interchange of oxygen and carbon dioxide between them. The lungs of vertebrates are blind sacs ; that is, there is one way in and out. To fill the lungs, breathing must be tidal rather than continuous. The internal structure of the lungs consists of a series of branching tubes that carry air to the alveoli (Figure 1). Alveoli, sometimes called air sacs, are tiny thin-walled, highly vascularized structures where respiratory gas exchange occurs. In the alveoli and throughout the body, the gases diffuse down their concentration gradients. This is usually expressed in terms of the partial pressures of the gases (PO2, PCO2) so that comparisons can be made easily between the concentrations of the gases in the atmosphere and in the body. This comparison is possible because the concentration of dissolved gas is proportional to the partial pressure of the gas, which is referred to as Henry's Law. Figure 1. A schematic diagram of the human respiratory system. The principal muscle activity in quiet breathing is rhythmic contraction of the diaphragm, a dome-shaped sheet of muscle that separates the thorax from the abdomen (Figure 2). During quiet inhalation, contraction of the diaphragm increases the volume of the chest, the intrathoracic pressure falls, and air flows into the lungs from the atmosphere down this pressure gradient. In quiet breathing, exhalation is Last updated on 1-Feb-18 Version: 5.0 Page 1 of 11

mainly passive. The diaphragm relaxes and the elastic recoil of the lungs raises intrathoracic gas pressure above atmospheric. Rib movements also occur in quiet breathing through the activity of the intercostal muscles, however the movements are small and thus contribute relatively little to respiration under these conditions. In forceful breathing, rib movements are obvious, and the volume enclosed by the ribcage changes to a greater extent. In addition, other muscles are recruited. The sternomastoid muscles of the neck assist in raising the sternum in forceful inhalation. During exhalation, abdominal muscles raise the pressure in the abdomen and push the relaxed diaphragm up, providing a powerful expiratory force. Figure 2. Diaphragmatic positions and changes in lung volume at the ends of inspiration and expiration. Breathing movements are unusual in that they are under dual control from the central nervous system. Breathing can be made voluntarily in the same way as arm and leg movements. However, if no conscious attention is focused on breathing, rhythmic muscle contractions occur spontaneously. Spontaneous breathing is controlled by the respiratory center in the medulla of the brain. The respiratory center ensures that gaseous exchange at the lung matches the requirements of the body. In times of increased demand, the rate and depth of breathing are increased to bring more fresh air into the lungs. The respiratory center has chemoreceptors that are sensitive to the partial pressure of carbon dioxide (PCO2) and ph of the cerebrospinal fluid. The respiratory center and the medullary cardiovascular center lie in close proximity in the medulla, and inspiratory neurons have an inhibitory effect on the vagal cardiac neurons of the heart. The normal variation in heart rate during respiration is referred to as respiratory sinus arrhythmia. Required Equipment LabChart software PowerLab Data Acquisition Unit Respiratory Belt Finger Pulse Transducer Medium-sized paper bag Reading material! Last updated on 1-Feb-18 Version: 5.0 Page 2 of 11

Procedure Equipment Setup (This will be done by your Lecturer) Make sure the PowerLab is turned off and the USB cable is connected to the computer. Connect the Respiratory Belt to Input 1 on the front panel of the PowerLab (Figure 3). The AD Instruments hardware needs to be connected and turned on before you open the settings file. Attach the Respiratory Belt around the volunteer s upper abdomen with the writing facing outward. It can be worn over a thin T-shirt. If the volunteer is wearing heavy clothing, such as a sweater, it needs to be removed. Refer to Figure 3 for proper placement. Check that the Respiratory Belt is properly connected to the volunteer and the PowerLab before proceeding. Turn on the PowerLab. Exercise 1: Normal Respiration Figure 3. Equipment Setup for PowerLab 26T In this exercise, you will investigate the characteristics of normal respiration and the ability to hold your breath after inhalation (inspiration) and exhalation (expiration). 1. Launch LabChart and open the settings file Breathing Settings. This has been provided to the lecturer. Have the volunteer sit in a relaxed position facing away from the monitor. Have the volunteer read to avoid conscious control of respiration. Select Input Amplifier from the Channel 1 Channel Function pop-up menu. Have the volunteer take deep, strong breaths. Observe the signal (Figure 4) and adjust the range in the dialog so that the maximum respiration occupies about one half to two-thirds of the full scale. Last updated on 1-Feb-18 Version: 5.0 Page 3 of 11

Figure 4. Input Amplifier Dialog Start recording. Have the volunteer breathe rapidly for five seconds and then breathe slowly. Examine the rate in Channel 2, and Autoscale. If the rate is not displayed properly, select Cyclic Measurements in the Channel 2 Channel Function pop-up menu. Make sure the event markers are detecting the peaks (Figure 5). Change the Detection Adjustment, if necessary by changing the minimum peak height value. Figure 5. Cyclic Measurements Dialog If the rate still is not displayed properly, repeat the procedure above. Also, make sure the volunteer is relaxed and is not consciously controlling their breathing. Note: If you change volunteers at any time during this experiment, you will need to determine the range again. When ready, Start recording. Add a comment with the volunteer s name and baseline. Have the volunteer breathe normally, and record for two to three minutes. Prepare a comment with inhale, hold. Tell the volunteer to take a deep breath and hold it for as long as possible, and add the comment immediately. Prepare a comment with breathe and when the volunteer begins to breathe again, add the comment. Last updated on 1-Feb-18 Version: 5.0 Page 4 of 11

Continue recording until a normal breathing pattern resumes. Stop recording, and save your data. Do not close the file. Exercise 2: Hyperventilation In this exercise, you will examine the effect of hyperventilation on the respiratory pattern and investigate the length of time the breath can be held. The volunteer may become dizzy while hyperventilating. If this occurs, stop the procedure, but record the respiratory response. If the volunteer feels unwell, have them breathe expired air by breathing into a paper bag for a short period. 1. Using the same file, Start recording. Add a comment with Exercise 2. 2. Record the volunteer s normal breathing for two to three minutes. Make sure the volunteer is still relaxed and facing away from the monitor. Prepare a comment with hyperventilate. 3. Have the volunteer hyperventilate by breathing as quickly and as deeply as possible for 30-45 seconds. Immediately add the comment. 4. Prepare a comment with breathe. After the 30-45 seconds (or as long as the volunteer is able to hyperventilate), add the comment and tell the volunteer to breathe normally. 5. Have the volunteer breathe normally for at least two minutes. Prepare another comment with hyperventilate. Repeat step 3 (ie hyperventilate for 30-45 seconds) 6. Prepare a comment with inhale, hold, and as soon as the thirty seconds of hyperventilation is complete, have the volunteer take a deep breath and hold it in for as long as possible. Immediately add the comment. 7. Prepare another comment with breathe, and add the comment when the volunteer breathes normally. Record for 30 seconds. Stop recording, and save your data. Do not close the file. Exercise 3: The Effect of Rebreathing In this exercise, you will investigate the effect of rebreathing on respiratory patterns. You will need the paper bag for this exercise. 1. Using the same file, Start recording. Add a comment with exercise 3. 2. Record the volunteer s normal breathing for two to three minutes. Make sure the volunteer is still relaxed and facing away from the monitor. 3. Add a comment with rebreathing, and immediately ask the volunteer to breathe into the paper bag. The volunteer should place the paper bag over their nose and mouth, forming a seal to stop air escaping to the atmosphere. Have the volunteer rebreathe for one minute. 4. Prepare a comment with breathe. After one minute, add the comment and tell the volunteer to remove the paper bag and breathe normally. 5. Continue recording for one minute. Save your data, and close the file. Exercise 4: Effect of increased airway resistance In this exercise, you will demonstrate the effects of bronchial obstructions, such as asthma, by making modifications to your equipment. Last updated on 1-Feb-18 Version: 5.0 Page 5 of 11

1. Your volunteer will need to place the nose clip over their nose. This will ensure that air is only being inhaled via the mouth. When this has been placed on your volunteer allow 2 minutes for them to adjust to breathing with this equipment on before doing any measurements. 2. Once they have adjusted to breathing with the nose clip add the comment breathe with nose clip. Record this breathing for 2 minutes. 3. Remove the mouthpiece and cover the end with medical tape which has a 1-2cm hole. This can be done with a sharpened pencil to make a one hole in the tape one centimeter in diameter. 4. Ask the volunteer to breath through this mouthpiece (with the nose clip) for 1-2 minutes (Or as long as they are comfortable). Add the comment breathe with restricted airway 4. Save your data. Do not close the file Exercise 5: Pulmonary Function Tests This exercise has been done for you and can be viewed by loading the mp4 movie Pulmonary Function Tests. In this video you will see how Vital Capacity / Forced Vital Capacity, Tidal Volume, FEV1 and Peak Flows are measured. The name of this file is Lab 2 Part 3.mp4. Analysis Exercise 1: Normal Respiration 1. Examine the data in the Chart View. Autoscale, if necessary. 2. Drag the Marker to the large peak following the comment inhale, hold. Move the Waveform Cursor to the start of the first breath afterwards, also preceded by a comment (Figure 7). Record the duration the breath was held, as shown in the Rate/Time display. Record the value in Table 1 of the Data Notebook. Last updated on 1-Feb-18 Version: 5.0 Page 6 of 11

Figure 7. Sample Data 3. Drag the Marker to the large peak following the comment exhale, hold. Move the Waveform Cursor to the start of the first breath afterwards. Record the duration the breath was held, as shown in the Rate/Time display. 4. Record the value in Table 1 of the Data Notebook. Exercise 2: Hyperventilation 1. Examine the data in the Chart View, and Autoscale, if necessary. 2. Use the data trace to determine the respiratory rate before and during hyperventilation. You can count the number of breathes per unit time to calculate the breathing rate before and during respiration. Record these values in Table 1 of the Data Notebook. 3. Use the Marker and Waveform Cursor as in the Analysis for Exercise 1 to determine the duration the breath was held following hyperventilation. 4. Record the value in Table 1 of the Data Notebook. Exercise 3: The Effect of Rebreathing 1. Examine the data in the Chart View, and Autoscale, if necessary. What is the effect of rebreathing on rate and depth of breathing and record the effects of rebreathing on the rate and depth of breathing in Table 2 2. Use the Marker and Waveform Cursor as in the Analysis for Exercise 1 to determine the depth of duration. (This is the height of the wave form) Last updated on 1-Feb-18 Version: 5.0 Page 7 of 11

Exercise 4: Effect of increased airway resistance 1. Examine the data in the Chart View, and Autoscale, if necessary. What is the effect of increased airway resistance on rate and depth of breathing and record the effects of rebreathing on the rate and depth of breathing in Table 2. 2. Use the Marker and Waveform Cursor as in the Analysis for Exercise 1 to determine the depth of duration. (This is the height of the wave form). Data Notebook Table 1. Normal Breathing and Hyperventilation Normal Breathing Respiratory Rate (BPM) Duration of Breath-holding (s) Hyperventilation Table 2. Effect of Rebreathing and Restricted Airway Normal Breathing Respiratory Rate (BPM) Respiratory Depth Rebreathing Restricted Airway Study Questions 1. In quiet breathing, muscular effort is required in inspiration, and expiration is largely passive, due to elastic recoiling of the lung. Do you see any differences in the rates of inspiration and expiration that may account for this? (Hint: How long did inspiration take and how long did expiration take) (4 marks) Last updated on 1-Feb-18 Version: 5.0 Page 8 of 11

2. The elastic recoil or compliance of the lungs are important properties of lung tissue. Describe what would happen if the lungs lost their recoil and became stiffer. If the lungs were to lose their elastic recoil how would you expel air from the lungs? (3 marks) 3. Can you explain in words what FEV1 is? FEV1 is used to diagnose airway diseases like asthma. What happens to FEV1 in someone with chronic asthma? What causes these changes? (6 marks) Last updated on 1-Feb-18 Version: 5.0 Page 9 of 11

4. Rebreathing from a closed bag results in increasing levels of CO2 in the blood. Did the depth and/or rate increase during rebreathing compared to normal breathing? Can you explain how increased levels of CO2 increases depth and rate of breathing? Your answer should include the central and peripheral chemoreceptors (8 marks) 5. Restricting the airway produced changes in the rate and depth of breathing. Can you explain why in a restricted airway the depth and rate of breathing increases? Your answer should include a discussion on factors that affect ventilation and gas exchange as well as central and peripheral chemoreceptors (8 marks) Last updated on 1-Feb-18 Version: 5.0 Page 10 of 11

6. Can you explain why you are able to breathe hold for longer after hyperventilating vs following normal breathing? Your answer should include a discussion on the levels of CO2 and what stimulates breathing (6 marks) Last updated on 1-Feb-18 Version: 5.0 Page 11 of 11