M56_MARI0000_00_SE_EX07.qxd 8/22/11 3:02 PM Page 389 7 E X E R C I S E Respiratory System Mechanics Advance Preparation/Comments 1. Demonstrate the mechanics of the lungs during respiration if a bell jar and balloon lungs are available. 2. Prior to the lab, suggest to the students that they become familiar with the exercise before coming to class. If students have a home computer, or access to a computer on campus, they can become familiar with the general operation of the simulations before coming to class. In particular, they should understand the lung volumes. 3. A short introductory presentation with the following elements is often helpful: Review the basics of respiratory anatomy, particularly the inspiratory and expiratory sequence. Reinforce the fact that there are no fibrous or muscular connections between the lungs and the thoracic wall when doing the bell jar demonstration. Students often remember this demonstration more than most others. Mention that normal inspiration requires muscle action but that normal expiration is passive. If a demonstration computer and bell jar lungs are available, compare the operation of the onscreen lungs with the balloon lungs in the bell jar. A pair of microscope slides with a thin film of water between makes an excellent demonstration of the concept of water tension. Briefly explain the idea of carbon dioxide retention in the blood during hypoventilation and its removal from the blood by hyperventilation. Review Boyle s Law. h. Remind students that the respiratory center in the brain is more sensitive to P CO2 than to P O2. Answers to Questions/Experimental Data Pre-lab Quiz in the Lab Manual 1. Expiration 2. c. inspiratory muscles relax 3. False 4. b. 500 ml 5. Vital capacity 6. False 7. aortic and carotid bodies 8. c. 7.4 0.02 9. Acids 10. False 389
M56_MARI0000_00_SE_EX07.qxd 8/22/11 3:02 PM Page 390 Activity 1: Measuring Respiratory Volumes and Calculating Capacities (pp. PEx-106 PEx-109) 6. 7485 Predict Question 1: When airway radius is decreased, will decrease proportionately. 11. 73.9% (3541/4791 100%) 12. 70% (436/621 100%) Chart 1: Respiratory Volumes and Capacities Radius (mm) Flow TV ERV IRV 5.00 7485 499 - - - - - - 5.00 7500 500 1200 3091 1200 4791 3541 5991 4.50 4920 328 787 2028 1613 3143 2303 4756 4.00 3075 205 492 1266 1908 1962 1422 3871 3.50 1800 120 288 742 2112 1150 872 3262 3.00 975 65 156 401 2244 621 436 2865 RV VC TLC 1. Residual volume is the air remaining in the airways and the lungs which prevents the alveoli from collapsing. 2. The helium dilution method is used to calculate the residual volume. 3. Prior to a cough, the respiratory rate will be regular on the spirogram. During a cough, the respiratory rate becomes irregular and there are more pronounced expiratory events. Activity 2: Comparative Spirometry (pp. PEx-109 PEx-112) Predict Question 1: The lung values that should change with emphysema include ERV, IRV, RV, FVC,, and (%). Predict Question 2: The lung values that should change with a patient suffering from an acute asthma attack include TV, ERV, IRV, RV, FVC,, and FEV1 (%). Predict Question 3: The lung values that change back when the asthma patient uses an inhaler include TV, ERV, and FEV1 (%). Predict Question 4: The lung value that should change more with moderate exercise is IRV. Chart 2: Spirometry Results Patient type TV ERV IRV Normal 500 1500 2000 1000 5000 6000 4000 80% Emphysema 500 750 2000 2750 3250 6000 1625 50% Acute Asthma Attack 300 750 2700 2250 3750 6000 1500 40% Plus Inhaler 500 1500 2800 1200 4800 6000 3840 80% Moderate Exercise 1875 1125 2000 1000 ND 6000 ND ND Heavy Exercise 3650 750 600 1000 ND 6000 ND ND RV FVC TLC (%) 390 Exercise 7
M56_MARI0000_00_SE_EX07.qxd 8/22/11 3:02 PM Page 391 1. With emphysema the lungs lose their elasticity resulting in more air remaining in the alveoli which increases the residual volume. 2. During an acute asthma attack, bronchiole smooth muscle spasms and, thus, the airways become restricted. The medication in the inhaler will partially dilate the airways, but the underlying cause for the asthma is still present. 3. The breathing rate and increase in tidal volume are more pronounced in the heavy exerciser than in the moderate exerciser. Activity 3: Effect of Surfactant and Intrapleural Pressure on Respiration (pp. PEx-112 PEx-113) Predict Question 1: Airflow will further increase with the addition of surfactant. Predict Question 2: The lung will remain collapsed with the valve closed. Chart 3: Effect of Surfactant and Intrapleural Pressure on Respiration Surfactant Intrapleural pressure left (atm) Intrapleural pressure right (atm) Airflow left Airflow right Total airflow 2 4 4 69.56 69.56 139.13 4 4 4 89.44 89.44 178.88 0 0.00 4 0.00 49.69 49.69 0 0.00 4 0.00 49.69 49.69 1. Premature infants have difficulty with normal breathing because they lack sufficient surfactant which decreases the surface tension in the alveoli. 2. The presence of air in the pleural cavity is referred to as a pneumothorax. When air is present in the pleural cavity, it can lead to the collapse of a lung, atelectasis. Exercise 7 391
M56_MARI0000_00_SE_EX07.qxd 8/22/11 3:02 PM Page 392 7 R E V I E W S H E E T EXERCISE Respiratory System Mechanics NAME LAB TIME/DATE A C T I V I T Y 1 Measuring Respiratory Volumes and Calculating Capacities 1. What would be an example of an everyday respiratory event the ERV button simulates? The ERV button simulates a forced expiration. 2. What additional skeletal muscles are utilized in an ERV activity? In forced expiration, abdominal-wall muscles and the internal intercostal muscles contract. 3. What was the (%) at the initial radius of 5.00 mm? The FEV1 (%) at a radius of 5 mm is 73.9% (3541/4791 100%). 4. What happened to the (%) as the radius of the airways decreased? How well did the results compare with your prediction? The FEV1 (%) decreased proportionally as the radius decreased. 5. Explain why the results from the experiment suggest that there is an obstructive, rather than a restrictive, pulmonary problem. The FEV1 (%) decreased proportionally as the radius decreased which is characteristic of an obstructive pulmonary problem. A C T I V I T Y 2 Comparative Spirometry 1. What lung values changed (from those of the normal patient) in the spirogram when the patient with emphysema was selected? Why did these values change as they did? How well did the results compare with your prediction? The values that change for the patient with emphysema are ERV, IRV, RV, FVC, and the FEV1 (%). These changes are due to the loss of elastic recoil. 2. Which of these two parameters changed more for the patient with emphysema, the FVC or the? The decreased significantly more than the FVC for the patient with emphysema. 3. What lung values changed (from those of the normal patient) in the spirogram when the patient experiencing an acute asthma attack was selected? Why did these values change as they did? How well did the results compare with your prediction? The values that changed for the patient with the acute asthma attack are TV, ERV, IRV, RV, FVC, and the FEV1 (%). These changes are due to the restriction of the airways. 4. How is having an acute asthma attack similar to having emphysema? How is it different? Both are similar because they are obstructive diseases characterized by increased airway resistance. It is more difficult to exhale with emphysema than with asthma. 392
M56_MARI0000_00_SE_EX07.qxd 8/22/11 3:02 PM Page 393 5. Describe the effect that the inhaler medication had on the asthmatic patient. Did all the spirogram values return to normal? Why do you think some values did not return all the way to normal? How well did the results compare with your prediction? The values that returned to normal were TV, ERV, FEV1 (%). The smooth muscles in the bronchioles didn t return to normal plus mucus still blocks the airway. 6. How much of an increase in do you think is required for it to be considered significantly improved by the medication? A significant improvement would be at least 10 15% improvement. Student answers will vary on this response. 7. With moderate aerobic exercise, which changed more from normal breathing, the ERV or the IRV? How well did the results compare with your prediction? The lung value that changed more with moderate exercise was IRV. 8. Compare the breathing rates during normal breathing, moderate exercise, and heavy exercise. The breathing rate increased with moderate and heavy exercise. A greater increase in breathing rate was seen with heavy exercise. A C T I V I T Y 3 Effect of Surfactant and Intrapleural Pressure on Respiration 1. What effect does the addition of surfactant have on the airflow? How well did the results compare with your prediction? The surfactant addition further increased airflow because the surface tension in the alveoli decreased allowing the alveoli to expand more. 2. Why does surfactant affect airflow in this manner? Surfactant serves to decrease the surface tension. 3. What effect did opening the valve have on the left lung? Why does this happen? It caused the lung to collapse because the pressure in the pleural cavity is less than the intrapulmonary pressure. Air flows from the lungs causing the collapse of the lung. 4. What effect on the collapsed lung in the left side of the glass bell jar did you observe when you closed the valve? How well did the results compare with your prediction? The lung did remain collapsed and did not reinflate after the valve was closed. 5. What emergency medical condition does opening the left valve simulate? Opening the left valve simulates a pneumothorax. 6. In the last part of this activity, you clicked the Reset button to draw the air out of the intrapleural space and return the lung to its normal resting condition. What emergency procedure would be used to achieve this result if these were the lungs in a living person? Emergency professionals will insert a chest tube to pull a partial vacuum out of the intrapleural space to return it to a value below atmospheric pressure. 7. What do you think would happen when the valve is opened if the two lungs were in a single large cavity rather than separate cavities? Both lungs would collapse if the lungs were not separated. Breathing would stop and the person would die. Review Sheet 7 393