Respiratory System Physiology- Critical thinking
1. What consequences would result if inflammation caused a buildup of fluid in the alveoli and interstitial spaces?
2. Premature infants with inadequate surfactant have decreased lung compliance (respiratory distress syndrome of the newborn). If surfactant is not available to administer for therapy, what can be done to inflate the lung?
3. What would be the effect of breathing through a plastic tube with a length of 20 cm and diameter of 4 cm? (Hint: Use the formula for the volume of a perfect cylinder).
4. What is the effect of exercise on PO2 at the end of a capillary in a normal region of the lung? In a region of the lung with diffusion limitation due to disease?
5. Researchers are developing blood substitutes to meet the demand for emergency transfusions. What would be the effect of artificial blood in which binding of O2 is not altered by acidity?
6. Several decades ago, removal of the carotid bodies was tried as a treatment for asthma. It was thought that it would reduce shortness of breath and airway hyper-reactivity. What would be the effect of bilateral carotid body removal on someone taking a trip to the top of a mountain (an altitude of 3000 meters)?
7. The existence of chemoreceptors in the pulmonary artery has been suggested. Hypothesize a function for peripheral chemoreceptors located on and sensing the PO2 and PCO2 of the blood in the pulmonary artery.
8. Billy’s normal alveolar ventilation rate (AVR) during mild exercise is 6.0 L/min. While at the beach on a warm summer day, he goes snorkeling. The snorkel has a volume of 50 mL. Assuming that the water is not too cold and that snorkeling is mild exercise for Billy, what would his respiratory rate have to be for him to maintain an AVR of 6.0 L/min while snorkeling? (Assume a constant tidal volume of 500 mL and an anatomic dead space of 150 mL.)
9. Mr. B. has had chronic advanced emphysema for 15 years. While hospitalized with a respiratory infection, he goes into respiratory distress. Without thinking, his nurse immediately administers pure oxygen, which causes Mr. B. to stop breathing. Why?
10. Cary hyperventilates for several minutes before diving into a swimming pool. After he enters and begins swimming underwater, he blacks out and almost drowns. What caused this to happen?
11. Why do individuals who are anemic generally not exhibit an increase in respiratory rate or tidal volume, even though their blood is not carrying enough oxygen?
12. Doris has an obstruction of her right primary bronchus. As a result, how would you expect the oxygen–hemoglobin saturation curve for her right lung to compare with that for her left?
13. Assume a normal female has a resting tidal volume of 400 mL, a respiratory rate of 13 breaths /min, and an anatomic dead space of 125 mL. When she exercises, which of the following scenarios would be most efficient for increasing her oxygen delivery to the lungs? (a) increase respiratory rate to 20 breaths /min but have no change in tidal volume (b) increase tidal volume to 550 mL but have no change in respiratory rate (c) increase tidal volume to 500 mL and respiratory rate to 15 breaths /min Which of these scenarios is most likely to occur during exercise in real life?
14. A 30-year-old computer programmer has had asthma for 15 years. When she lies down at night, she has spells of wheezing and coughing. Over the years, she has found that she can breathe better if she sleeps sitting nearly upright. Upon examination, her doctor fnds that she has an enlarged thorax. Her lungs are overinflated on X-ray. Here are the results of her examination and pulmonary function tests.
Ventilation rate: 16 breaths/min
Tidal volume: 600 mL
ERV: 1000 mL
RV: 3500 mL
Inspiratory capacity: 1800 mL
Vital capacity: 2800 mL
Functional residual capacity: 4500 mL
TLC: 6300 mL
After she is given a bronchodilator, her vital capacity increased to 3650 mL. (a) What is her minute volume? (b) Explain the change in vital capacity with bronchodilators. (c) Which other values are abnormal? Can you explain why they might be, given her history and findings?
15. A container of gas with a movable piston has a volume of 500 mL and a pressure of 60 mm Hg. The piston is moved, and the new pressure is 150 mm Hg. What is the new volume of the container?
16. You have a mixture of gases in dry air, with an atmospheric pressure of 760 mm Hg. Calculate the partial pressure of each gas if the composition of the air is: (a) 21% oxygen, 78% nitrogen, 0.3% carbon dioxide (b) 40% oxygen, 13% nitrogen, 45% carbon dioxide, 2% hydrogen (c) 10% oxygen, 15% nitrogen, 1% argon, 25% carbon dioxide
17. Li is a tiny woman, with a tidal volume of 400 mL and a respiratory rate of 12 breaths per minute at rest. What is her total pulmonary ventilation? Just before a physiology exam, her ventilation increases to 18 breaths per minute from nervousness. Now what is her total pulmonary ventilation? Assuming her anatomic dead space is 120 mL, what is her alveolar ventilation in each case?
18. You collected the following data on your classmate Neelesh:
Minute volume = 5004 mL/min
Respiratory rate = 3 breaths/15 sec
Vital capacity = 4800 mL
Expiratory reserve volume = 1000 mL
What are Neelesh’s tidal volume and inspiratory reserve volume?
19. Use the figure below to help solve this problem. A spirometer with a volume of 1 liter (V1) is filled with a mixture of oxygen and helium, with the helium concentration being 4 g/L (C1). Helium does not move from the lungs into the blood or from the blood into the lungs. A subject is told to blow out all the air he possibly can. Once he finishes that exhalation, his lung volume is V2. He then puts the spirometer tube in his mouth and breathes quietly for several breaths. At the end of that time, the helium is evenly dispersed in the spirometer and the subject’s lungs. A measurement shows the new concentration of helium is 1.9 g/L. What was the subject’s lung volume at the start of the experiment? (Hint: C1xV1 = C2xV2)
20. The graph shows one lung under two different conditions, A
and B. What does this graph show? (a) the effect of lung volume on pressure, or
(b) the effect of pressure on lung volume? In which condition does the lung
have higher compliance, or is compliance the same in the two situations?
21. Marco tries to hide at the bottom of a swimming hole by breathing in and out through two feet of garden hose, which greatly increases his anatomic dead space. What happens to the following parameters in his arterial blood, and why? (a) PCO2 (c) bicarbonate ion (b) PO2 (d) pH
22. Which person carries more oxygen in his blood? (a) one with Hb of 15 g/dL and arterial PO2 of 80 mm Hg (b) one with Hb of 12 g/dL and arterial PO2 of 100 mm Hg.
23. What would happen to each of the following parameters in a person suffering from pulmonary edema? (a) arterial PO2 (b) arterial hemoglobin saturation (c) alveolar ventilation.
24. In early research on the control of rhythmic breathing, scientists made the following observations. What hypotheses might the researchers have formulated from each observation? (a) Observation. If the brain stem is severed below the medulla, all respiratory movement ceases. (b) Observation. If the brain stem is severed above the level of the pons, ventilation is normal. (c) Observation. If the medulla is completely separated from the pons and higher brain centers, ventilation becomes irregular but a pattern of inspiration/expiration remains.
25. A hospitalized patient with severe chronic obstructive lung disease has a PCO2 of 55 mm Hg and a PO2 of 50 mm Hg. To elevate his blood oxygen, he is given pure oxygen through a nasal tube. Te patient immediately stops breathing. Explain why this might occur.
26. You are a physiologist on a space flight to a distant planet. You find intelligent humanoid creatures inhabiting the planet, and they willingly submit to your tests. Some of the data you have collected are described in the figure. The graph shows the oxygen saturation curve for the oxygen-carrying molecule in the blood of the humanoid named Bzork. Bzork’s normal alveolar PO2 is 85 mm Hg. His normal cell PO2 is 20 mm Hg, but it drops to 10 mm Hg with exercise. (a) What is the percent saturation for Bzork’s oxygen-carrying molecule in blood at the alveoli? In blood at an exercising cell? (b) Based on the graph above, what conclusions can you draw about Bzork’s oxygen requirements during normal activity and during exercise?
27. The next experiment on Bzork involves his ventilatory response to different conditions (figure). The data from that experiment are graphed before. Interpret the results of experiments A and C.
28. The alveolar epithelium is an absorptive epithelium and is able to transport ions from the fluid lining of alveoli into the interstitial space, creating an osmotic gradient for water to follow. Draw an alveolar epithelium and label apical and basolateral surfaces, the airspace, and interstitial fluid. Arrange the following proteins on the cell membrane so that the epithelium absorbs sodium and water: aquaporins, Na+ -K + -ATPase, epithelial Na+ channel (ENaC). (Remember: Na+ concentrations are higher in the ECF than in the ICF.)
29. You are given the following information on a patient.
Blood volume = 5.2 liters
Hematocrit = 47%
Hemoglobin concentration = 12 g/dL whole blood.
Total amount of oxygen carried in blood = 1015 mL.
Arterial plasma PO2 = 100 mm Hg.
You know that when plasma PO2 is 100 mm Hg, plasma contains 0.3 mL O2/dL, and that hemoglobin is 98% saturated. Each hemoglobin molecule can bind to a maximum of four molecules of oxygen.
Using this information, calculate the maximum oxygencarrying capacity of hemoglobin (100% saturated). Units will be mL O2/g Hb.
30. Adolph Fick, the nineteenth-century physiologist who derived Fick’s law of diffusion, also developed the Fick equation that relates oxygen consumption, cardiac output, and blood oxygen content: O2 consumption = cardiac output: (arterial oxygen content - venous oxgen content). A person has a cardiac output of 4.5 L/min, an arterial oxygen content of 105 mL O2/L blood, and a vena cava oxygen content of 50 mL O2/L blood. What is this person’s oxygen consumption?
31. Describe what happens to the oxygen-hemoglobin saturation curve in Figure when blood hemoglobin falls from 15 g/dL blood to 10 g/dL blood
32. Keith M., a former heavy cigarette smoker, has severe emphysema. How does this condition affect his airway resistance? How does this change in airway resistance influence Keith’s inspiratory and expiratory efforts? Describe how his respiratory muscle activity and intra-alveolar pressure changes compare to normal to accomplish a normal tidal volume. How would his spirogram compare to normal? What influence would Keith’s condition have on gas exchange in his lungs? What blood-gas abnormalities are likely to be present? Would it be appropriate to administer O2 to Keith to relieve his hypoxic condition?
33. Why is it important that airplane interiors are pressurized (that is, the pressure is maintained at sea-level atmospheric pressure even though the atmospheric pressure surrounding the plane is substantially lower)? Explain the physiological value of using O2 masks if the pressure in the airplane interior cannot be maintained.
34. If a severely anemic person has normal lungs, indicate whether each of the following factors will be normal, below normal, or above normal: (a) alveolar PO2, (b) arterial PO2, (c) percent hemoglobin saturation, (d) total O2 content of arterial blood, (e) tissue PO2, (f) total O2 transferred from blood to tissues
35. Would hypercapnia accompany the hypoxia produced in each of the following situations? Why or why not? a. cyanide poisoning b. pulmonary edema c. restrictive lung disease d. high altitude e. severe anemia f. congestive heart failure g. obstructive lung disease
36. Based on what you know about the control of respiration, explain why it is dangerous to voluntarily hyperventilate to lower the arterial PCO2 before going underwater. The purpose of the hyperventilation is to stay under longer before PCO2 rises above normal and drives the swimmer to surface for a breath of air.
37. If a person whose alveolar–capillary membranes are thickened by disease has an alveolar PO2 of 100 mm Hg and an alveolar PCO2 of 40 mm Hg, which of the following values of systemic arterial blood gases are most likely to exist?
a. PO2 = 105 mm Hg, PCO2 = 35 mm Hg
b. PO2 = 100 mm Hg, PCO2 = 40 mm Hg
c. PO2 5 80 mm Hg, PCO2 = 45 mm Hg
If the person is administered 100% O2, will the arterial PO2 increase, decrease, or remain the same? Will the arterial PCO2 increase, decrease, or remain the same?
38. Why would enlarged tonsils or adenoids cause obstructive sleep apnea (OSA)?
39. Long-term smokers often develop a chronic cough. a. What purpose does the smokers’ cough serve? b. Why are nonsmokers less likely to develop a chronic cough?
40. Professional singers who need to hold a long note while singing must exert a great deal of control over their breathing. What muscle(s) needs/need conditioning to acquire better control over their breathing?
41. Why would someone who nearly drowned have a blue tint to his or her skin?
42. Billy’s normal alveolar ventilation rate (AVR) during mild exercise is 6.0 l/min. While at the beach on a warm summer day, he goes snorkeling. The snorkel has a volume of 50 ml. Assuming that the water is not too cold and that snorkeling is mild exercise for Billy, what would his respiratory rate have to be for him to maintain an AVR of 6.0 l/min while snorkeling? (Assume a constant tidal volume of 500 ml and an anatomic dead space of 150 ml.)
43. Mr. B. has had chronic advanced emphysema for 15 years. While hospitalized with a respiratory infection, he goes into respiratory distress. Without thinking, his nurse immediately administers pure oxygen, which causes Mr. B. to stop breathing. Why?
44. Cary hyperventilates for several minutes before diving into a swimming pool. After he enters and begins swimming underwater, he blacks out and almost drowns. What caused this to happen?
45. Why do individuals who are anemic generally not exhibit an increase in respiratory rate or tidal volume, even though their blood is not carrying enough oxygen?
46. Doris has an obstruction of her right primary bronchus. As a result, how would you expect the oxygen–hemoglobin saturation curve for her right lung to compare with that for her left?
47. A person’s vital capacity is measured while standing and while lying down. What difference, if any, in the measurement do you predict and why?
48. Ima Diver wanted to do some underwater exploration. Instead of buying expensive SCUBA equipment, she obtained a long hose and an innertube. She attached one end of the hose to the innertube so that the end was always out of the water, and she inserted the other end of the hose in her mouth and went diving. What happened to her alveolar ventilation and why? How can she compensate for this change? How does diving affect lung compliance and the work of ventilation?
49. The bacteria that cause gangrene (Clostridium perfringens) are anaerobic microorganisms that do not thrive in the presence of oxygen. Hyperbaric oxygenation (HBO) treatment places a person in a chamber containing oxygen at three to four times normal atmospheric pressure. Explain how HBO helps treat gangrene.
50. One technique for artificial respiration is mouth-to-mouth resuscitation. The rescuer takes a deep breath, blows air into the patient’s mouth, and then lets air flow out. The process is repeated. Explain the following: (1) Why do the patient’s lungs expand? (2) Why does air move out of the patient’s lungs? (3) What effect do the Po2 and the Pco2 of the rescuer’s air have on the victim?
51. The left phrenic nerve supplies the left side of the diaphragm, and the right phrenic nerve supplies the right side. Damage to the left phrenic nerve results in paralysis of the left side of the diaphragm. During inspiration, does the left side of the diaphragm move superiorly, move inferiorly, or stay in place?
52. Suppose that the thoracic wall is punctured at the end of a normal expiration, producing a pneumothorax. Does the thoracic wall move inward, move outward, or not move at all?
53. During normal, quiet respiration, when does the maximum rate of diffusion of oxygen in the pulmonary capillaries occur? When does the maximum rate of diffusion of carbon dioxide occur?
54. Experimental evidence suggests that the overuse of erythropoietin (EPO; see chapter 19) reduces athletic performance. What side effects of EPO abuse reduce exercise stamina?
55. Predict what would happen to tidal volume if (a) the vagus nerves were cut, (b) the phrenic nerves were cut, or (c) the intercostal nerves were cut.
56. You and your physiology instructor are trapped in an overturned ship. To escape, you must swim under water a long distance. You tell your instructor it would be a good idea to hyperventilate before making the escape attempt. Your instructor calmly replies, “What good would that do, since your pulmonary capillaries are already 100% saturated with oxygen?” What should you do and why?
57. Ima Anxious was hysterical and hyperventilating, so a doctor made her breathe into a paper bag. An especially astute student said to the doctor, “When Ima was hyperventilating, she was reducing blood carbon dioxide levels; when she breathed into the paper bag, carbon dioxide was trapped in the bag, and she was rebreathing it, thus causing blood carbon dioxide levels to increase. As Ima’s blood carbon dioxide levels increased, her urge to breathe should have increased. Instead, she began to breathe more slowly. Please explain.” How do you think the doctor responded? (Hint: Recall that the effect of decreased blood carbon dioxide on the vasomotor center results in vasodilation and a sudden decrease in blood pressure.)