Pulmonary Quiz 2

Question 1

A 15 year old student complaining of dyspnea was admitted to the ER. Because he appeared cyanotic, his arterial blood gases were determined. The results are: PaCO₂ = 52 mm Hg, PaO₂ = 70 mm Hg, pH = 7.3. The metabolic rate (oxygen uptake) was 250 ml/min and R = 0.8.

What is the calculated alveolar ventilation of this patient?

(a) 4322 ml/min
(b) 4568 ml/min
(c) 3319 ml/min
(d) 5650 ml/min
(e) 2200 ml/min

Answer 1

Explanation: C is correct: V_A = (VCO₂/PaCO₂) x 863. VCO₂ is not given in the question, but can be calculated from VO₂ and R, because R = VCO₂/VO₂. Therefore, VCO₂ = R x VO₂ = 0.8 x 250 = 200 ml/min. Using this and other given values in the above equation results in V_A = (200/52) x 863 = 3319 ml/min

Question 2

A patient connected to a ventilator is accidentally hyperventilated. Which of the following is the most likely outcome?

(a) Lowered PaO₂; lowered PaCO₂
(b) No change in PaCO₂; lowered PaCO₂
(c) Elevated PaO₂; lowered PaCO₂
(d) Elevated arterial PaO₂; elevated arterial PaCO₂
(e) Lowered arterial PaO₂; elevated PaCO₂

Answer 2

Explanation: C is correct: Due to definition of hyperventilation, the alveolar ventilation must have been increased to reduce PaCO2. An increased alveolar ventilation also increases PaO2 in this situation.

Question 3

A survivor of a house fire is taken to the ER. He is comatose but breathing normal. His skin color is cherry red. Carbon monoxide poisoning is suspected. Which of the following blood findings is expected?

(a) Increased arterial PCO₂
(b) Decreased arterial PCO₂
(c) Decreased hemoglobin-oxygen affinity
(d) Decreased arterial PO₂
(e) Decreased arterial O₂ concentration

Answer 3

Explanation: E is correct: CO poisoning reduces O2 concentration, but does not affect PO2 or PCO2. It also increases the affinity of unoccupied hemoglobin for O2.

Question 4

A volunteer in the physiology lab is preparing to do a maximum oxygen uptake test. His metabolic rate is measured at rest and he is found to have an oxygen uptake of 250 ml/min and a carbon dioxide output of 200 ml/min. He begins pedaling and after a few minutes his oxygen uptake is 600 ml/min and his carbon dioxide output is also 600 ml/min. If there is no change in inspired PO₂ or in his alveolar PCO₂, what change in his alveolar PO₂ may occur?

(a) Increase
(b) Decrease then go back to normal
(c) Decrease
(d) No change
(e) Decrease, then increase

Answer 4

Explanation: A is correct: P_AO₂ = PIO₂ – (P_ACO₂/R). The question suggests that PIO₂ and P_ACO₂ remain unchanged, and due to the data given R is increased from 0.8 to 1.0. Therefore, in the above equation P_ACO₂ would increase by an increased R at constant PIO₂ and P_ACO₂.

Question 5

VA/Q mismatch is partially compensated by local reflexes in the pulmonary vasculature and in the airways. Which are these reflexes?

(a) Vasoconstriction due to low arterial PO2; bronchoconstriction due to high PCO2
(b) Vasodilation due to low alveolar PCO2; bronchoconstriction due to high alveolar PCO2
(c) Vasoconstriction due to low alveolar PO2; bronchoconstriction due to low alveolar PCO2
(d) Vasodilation due to high alveolar PO2; bronchoconstriction due to low alveolar PO2

Answer 5

Hypocapnic bronchodilation & hypoxic vasoconstriction

Explanation: C is correct. Hypoxic pulmonary vasoconstriction is caused by alveolar hypoxia and not by hypoxic blood with normal alveolar PO2. The mechanism is that alveolar hypoxia inhibits a K+ channel in the vascular smooth muscle cells and depolarizes the cells. As a result voltage gated Ca++ channels are opening and the Ca++ release into the cells causes contraction of vascular muscle cells. Bronchoconstriction is mediated by Low PCO2 of airways.

Question 6

A patient in the intensive care unit is connected to a metabolic cart for measurement of basal metabolic rate. His CO₂ output is 300 ml/min. His alveolar ventilation is assumed to be 4000 ml/L. what would be his arterial PCO₂?

(a) 40 mm Hg
(b) 15 mm Hg
(c) 120 mm Hg
(d) 90 mm Hg
(e) 65 mm Hg

Answer 6

Explanation: E is correct. PaCO₂ = (VCO₂/V_A) x 863 = (300/4000) x 863 = 65 mmHg

Question 7

A patient with α Thalasemmia (Hemoglobin H) requires periodic blood transfusions. What is the type of hypoxia, characterized by low arterial oxygen content but normal saturation and normal arterial PO2?

(a) Histotoxic hypoxia
(b) Anemic hypoxia
(c) Stagnant hypoxia
(d) Arterial hypoxia (hypoxemia)

Answer 7

Explanation: B is correct: By anemia both PO2 and O2 saturation are normal, but O2 concentration is reduced.

Question 8

Which of the following situations is most likely to result in a right shift of the oxyhemoglobin dissociation curve?

(a) Low cellular phosphate concentrations
(b) Hypothermia during cold water immersion
(c) Hyperventilation induced by anxiety
(d) Anemia from iron deficiency
(e) Fever due to bacterial infection

Answer 8

Explanation: E is correct: Increase in temperature; High Body temperature reduces the O2 affinity of Hb and shifts the O2 dissociation curve to the right

Question 9

Occasionally the respiratory center of the brain receives simultaneously conflicting inputs from the peripheral and central chemoreceptors; i.e., stimulation and inhibition. Which of the following would produce such a conflicting influence on respiratory center?

(a) Angina pectoris
(b) Valsalva maneuver
(c) Arterial hypoxia
(d) Metabolic acidosis
(e) Respiratory acidosis

Answer 9

Explanation: C is correct: Hypoxemia increases ventilation through stimulation of peripheral chemoreceptors. As a result of increased ventilation PaCO2 decreases and pH increases and both inhibit ventilation through inhibition of central chemoreceptors.

Question 10

Which of the following correctly describes the type of blood flowing in the corresponding vessels?

(a) Thebesian veins carrying oxygenated blood; pulmonary artery carrying deoxygenated blood
(b) Pulmonary artery carrying oxygenated blood; bronchial artery carrying deoxygenated blood
(c) Bronchial artery carrying oxygenated blood; pulmonary artery carrying oxygenated blood
(d) Bronchial artery carrying oxygenated blood; pulmonary artery carrying deoxygenated blood.

Answer 10

Explanation: D is correct: All arteries are carrying oxygenated blood with exception of Pulmonary arteries carrying deoxygenated blood. All veins are carrying deoxygenated blood with exception of Pulmonary veins carrying oxygenated blood.

Thebesian veins draining into the left heart, along with deoxygenated blood originating from the bronchial veins draining into the pulmonary veins, contribute to normal physiologic shunting of blood

Question 11

The world’s highest summit (Mt. Everest) is 29,035 ft. and the barometric pressure is 247 mm Hg. As of 2007, 2000 climbers have reached the summit and 200 have died trying. On May 8, 1978, Reinhold Messener and Peter Habeler achieved what was thought to be impossible, the first ascent of Mt. Everest without oxygen. The inspired PO2 of these climbers at the summit would be about:

(a) 34 mm Hg
(b) 147 mm Hg
(c) 100 mm Hg
(d) 66 mm Hg
(e) 42 mm Hg

Answer 11

Explanation: E is correct: PIO₂ = FIO₂ x (PB – PH₂O) = 0.21 x (247 – 47) = 42 mmHg

Question 12

A 28 y.o. male with anemia ([Hb] = 10g/dL) is admitted to the ER complaining of chest pain. His ventilation and pulmonary gas exchange appeared to be normal. Which blood gas partial pressure and contents will be found in blood of this patient?

(a) Reduced arterial PO2 and increased arterial oxygen content
(b) Increased arterial PO2 and normal arterial oxygen content
(c) Reduced arterial PO2 and normal arterial oxygen content
(d) Normal arterial PO2 and normal arterial oxygen content
(e) Normal arterial PO2 and reduced arterial oxygen content

Answer 12

Explanation: E is correct: Arterial PO2 and arterial O2 saturation will be normal at a normal ventilation and normal pulmonary gas exchange. A Reduced Hb concentration causes a decrease in arterial O2 concentration despite of a normal PaO2.

Question 13

A patient on a ventilator is receiving supplemental oxygen and has an arterial PO₂ of 200 mmHg and a hemoglobin concentration of 20 g/dL. What would her arterial oxygen content be in ml/dL:

O₂ carried by Hb Dissolved O₂ Total O2

1. 20.1 - 0.3 -20.4
2. 25.2 - 3 - 28.2
3. 15 - 0.03 - 15.03
4. 26.8 - 0.6 - 27.4

Answer 13

Explanation: D is correct: Each g Hb binds 1.34 ml O2. Therefore, O2 bound with 20 g hemoglobin = 20 X 1.34 = 26.8ml/dL. Dissolved O2 concentration = PO2 X alpha O2 = 200 X 0.003 = 0.6 ml/dL. Total O2 concentration is the sum of the two = 27.6 ml/dL.

Question 14

Some swimmers hyperventilate prior to seeing how far they can swim underwater without surfacing for a breath. This techniques is effective in prolonging breath holding time. The main reason is that hyperventilation:

(a) Increases blood oxygen saturation so the dive can last longer
(b) Increases the time before the carotid body PO2 receptors increase their firing
(c) Increases the time before carotid and central PCO2/pH receptors increase their firing
(d) Inhibits the slow and fast pulmonary stretch receptors

Answer 14

Explanation: C is correct: Hyperventilation reduces arterial PCO2. Therefore, the person can hold his breath longer in this situation until CO2 accumulated in the body reaches a level that is able to stimulate peripheral and central chemoreceptors and force the person to breathe.

Question 15

Which of the following is most likely to increase the diffusing capacity of the lungs in health or disease?

(a) Pulmonary hypotension
(b) Tricuspid stenosis
(c) Moderate exercise
(d) Interstitial edema

Answer 15

Explanation: C is correct: Cardiac output increases during moderate exercise and causes recruitment and distension of the pulmonary vessels and thus increases the gas exchange surface area in the lungs. All other choices do the opposite and are, therefore, wrong

Question 16

A 26-year old patient has a cardiac output of 5 L/min and mean pulmonary arterial and left atrial pressures of 20 and 5 mm Hg, respectively. What is her pulmonary vascular resistance?

(a) 0.33 mm Hg/L per minute
(b) 0.25 mm Hg/L per minute
(c) 4 mm Hg/L per minute
(d) 3 mm Hg/L per minute

Answer 16

Explanation: D is correct: PVR = (Pulmonary artery pressure – Left atrial pressure) / Cardiac output = (20 – 5) / 5 = 3 mmHg/L x min

Question 17

Which of the following combinations best described the properties of central chemoreceptors and their effects on ventilation?

(a) Central chemoreceptor is H+ receptor and accounts for 20% of the total ventilatory response to altered PCO2
(b) Central chemoreceptor responds directly to changing PCO2 and accounts for 80% of the total ventilator response to altered PCO2
(c) Central chemoreceptor is H+ receptor and accounts for 80% of the total ventilatory response to altered PCO2
(d) Central chemoreceptor responds directly to changing PCO2 and accounts for 20% of the total ventilatory response to altered PCO2
(e) Central chemoreceptor is O2 receptor and accounts for 20% of ventilator response to PO2

Answer 17

Explanation: C is correct: these facts are themselves the explanations

Question 18

A person suffering from pulmonary embolism is observed to be cyanotic and to have rapid, shallow breathing. Which pulmonary receptors or reflexes caused the rapid, shallow breathing in this patient?

(a) Valsalva reflex
(b) C-fibers or typ “J” receptors
(c) Baroreceptor reflex from low blood pressure
(d) Hering Breuer reflex from hyper inflated lungs
(e) Irritant receptors

Answer 18

Explanation: B is correct: Rapid shallow breathing is produced by stimulation of pulmonary C-fibers.

Question 19

A 35 year old male was admitted to the ER with suspected overdose of heroin. He was referred to the pulmonary function lab for conducting spirometry and measurement of diffusing capacity (DL). The PCO in alveolar gas was 0.5 mm Hg and the CO uptake rate equaled 20 ml/min. What is the CO diffusing capacity of this patient in ml/min/mm Hg?

(a) 28
(b) 40
(c) 35
(d) 56
(e) 60

Answer 19

Explanation: B is correct: DL_CO = V_CO / P_ACO = 20/0.5 = 40 mmHg

Question 20

After eating two improperly processed manioc roots (cassava) a Ross student is admitted to the ER complaining of weakness, shortness of breath, dizziness. He is confused and his skin appears cherry red. The diagnosis is cyanide poisoning. What is this type of hypoxia that prevents oxygen uptake by cells?

(a) Stagnant hypoxia
(b) Anemic hypoxia
(c) Arterial hypoxia (hypoxemia)
(d) Histotoxic hypoxia

Answer 20

Explanation: D is correct: Histotoxic hypoxia occurs when Mitochondrion are unable to use O2 for production of ATP. Cyanide poisoning interferes with cytochromes function and blocks usage of oxygen for energy production.

(a) Stagnant hypoxia: decreased rate of blood flow; arterial PO2 and PCO2 are normal
(b) Anemic hypoxia: O2 concentration reduced, but arterial PO2 normal –> CO poisoning or oxidation of Hb which prevents binding causing hypoxia
(c) Arterial hypoxia (hypoxemia): O2 delivery to tissues reduced by reduction in arterial O2 saturation (5 types)

Question 21

What fraction of oxygen do climbers at the summit of Mt. Everest (PB = 247 mm Hg) need to have a normal value of 150 mm Hg for inspired PO2?

(a) 0.75 (75%)
(b) 0.50 (50%)
(c) 0.1 (10%)
(d) 0.21 (21%)
(e) 1.0 (100%)

Answer 21

Explanation: PIO₂ = FIO₂ x (P_B – PH₂O). From this equation FIO₂ = PIO2 / (P_B – PH₂O) = 150 / (247-47) = 150 / 200 = 0.75 or 75%

Question 22

During strenuous exercise, a patient’s cardiac output was measured at 12 L/min. Assuming a pulmonary capillary volume of 200 ml, what will be the estimated pulmonary capillary transit time in second?

(a) 2.0
(b) 0.75
(c) 0.5
(d) 1.5
(e) 1.0

Answer 22

Explanation: E is correct: Transit time = Volume / Flow = 200 mL / 12 L/min = 200 mL / 12000 mL / 60 sec = 1 sec

Question 23

Regional differences in ventilation perfusion ratios affect gas tensions in the pulmonary blood. Which regional gas tensions will be observed in the blood leaving the alveolar capillaries of a healthy standing individual?

O₂ tension (PO₂) CO₂ tension (PCO₂)

1) Lowest at base Highest at apex
2) Highest at base Lowest at base
3) Highest at apex Lowest at apex
4) Highest at apex Lowest at base
5) Lowest at base Lowest at base

Answer 23

Explanation: C is correct: At apex both ventilation and perfusion are lower than at the base of the lung. However, the ventilation/perfusion ratio is higher at the apex, because the increase of blood flow towards base is larger than the increase of ventilation towards base, which makes ventilation to perfusion ratio smaller at the base. However, blood PO2 and PCO2 are determined by the ventilation/perfusion ratio and the higher ratio at the apex produces a higher PO2 and a lower PCO2 at the apex.

Question 24

Which of the following circulatory parameters best characterizes the pulmonary circulation in comparison to systemic circulation?

Flow Pressure Resistance Compliance

(1) Lower-Higher-Lower-Higher
(2) Equal-Lower-Higher-Lower
(3) Lower-Lower-Lower-Higher
(4) Equal-Lower-Higher-Higher
(5) Equal-Lower-Lower-Higher

Answer 24

Explanation: 5 is correct: These are biological facts and do not require reasoning.

Question 25

A patient with emphysema and heart failure is taken to the emergency room after complaining of shortness of breath. The following values are obtained from pulmonary catheterization:

Cardiac output: 3L/min; mean pulmonary artery pressure = 40 mmHg; left atrial pressure = 30 mmHg; mean aortic pressure = 62 mmHg; mean right atrial pressure = 2 mmHg. What is the pulmonary vascular resistance of this patient in mmHg/L/min?

(a) 16.3
(b) 10
(c) 20
(d) 3.3
(e) 1.6

Answer 25

Explanation: D is correct: PVR = (Pulmonary artery pressure – Left atrial pressure) / Cardiac output = (40 – 30) / 3 = 3.3

Question 26

. Successful mountain climbers usually spend several days at each camp prior to climbing. One of the reasons for this is that acclimation to high altitude is characterized by a moderate increase in ventilation followed several days later with a larger increase in ventilation. What is the cause of this delayed increase in ventilation?

(a) A renal compensation of initial alkalosis that inhibited ventilation
(b) A delayed cerebral vasoconstriction that stimulates ventilation
(c) A delayed production of progesterone that stimulates ventilation
(d) A delayed production of lactic acid that stimulates breathing

Answer 26

Explanation: A is correct: Hypoxia increases ventilation, which results in a decreased PCO₂ and an increased pH. This increase in pH inhibits ventilation. Kidney compensates the pH change within a few days, which causes the relief of ventilatory inhibition and results in a further increase in ventilation.

Question 27

. Which process facilitates the oxygen uptake by the fetal circulation as it traverses the placenta?

(a) Lower pH of umbilical venous blood
(b) Lower affinity of fetal hemoglobin
(c) Thinner diffusion barrier
(d) A double Bohr effect

Answer 27

Explanation: D is correct: Bohr effect on the mother side causes mother hemoglobin to release O2 and Bohr effect on fetus side increases the affinity of fetus hemoglobin to bind O2 easier.

Question 28

What is the effect of transection of the glossopharyngeal nerve on the ventilatory responses to hypercapnia and hypoxia?

Responses to hypercapnia - Response to hypoxia

1. Reduced by 20% - Absent or depressed
2. Reduced by 80% - Normal
3. Normal - Increased
4. Absent - Absent

Answer 28

Explanation: B is correct: Peripheral chemoreceptors are responsible 100% for respiratory response to hypoxia and 20% for the response to changes in PCO2 or H+.

Question 29

Following a bilateral lung transplant, a patient demonstrated an impressive ability to hold his breath. Absence of which receptors is most likely responsible for the ability of this patient to hold his breath?

(a) Placebo effect
(b) Absent of input from lung mechanoreceptors (Hering Breuer)
(c) Absent of input from carotid body O2 chemoreceptors
(d) Absent of input from baroreceptors
(e) Absent of input from carotid body CO2 chemoreceptors

Answer 29

Explanation: B is correct: Slowly adapting pulmonary stretch receptors are stimulated by lung inflation and try to terminate inspiration of a large volume. If they are absent in transplant lung, a large breath can be taken and the breath can also be held for longer than normal.

Question 30

At the same PCO₂ venous blood will contain more CO₂ than arterial blood. Which of the following effects or laws is responsible for this?

(a) Bohr effect
(b) Haldane effect
(c) Starling law
(d) Hamburger effect
(e) Fick’s law

Answer 30

Explanation: B is correct: Venous blood contains less O2 than arterial blood and therefore, can bind more CO2 due to Haldane effect –> Oxygenation of blood in the lungs displaces carbon dioxide from hemoglobin which increases the removal of carbon dioxide.

Bohr effect: a decrease in the amount of oxygen associated with hemoglobin and other respiratory compounds in response to a lowered blood pH resulting from an increased concentration of carbon dioxide in the blood.

Fick’s Law essentially states that the rate of diffusion of a gas across a permeable membrane is determined by the chemical nature of the membrane itself, the surface area of the membrane, the partial pressure gradient of the gas across the membrane, and the thickness of the membrane –> V’gas = D * A * ΔP/T

Question 31

If Messener and Habeler had not hyperventilated at the summit of Mt. Everest (PB = 247 mm Hg), their arterial PCO2 would have been at sea level value of 40 mm Hg. Assuming that R = 1, what would have been their alveolar PO2?

(a) 2 mm Hg
(b) 20 mm Hg
(c) 34 mm Hg
(d) 16 mm Hg
(e) 11 mm Hg

Answer 31

Explanation: P_AO₂ = PIO₂ – (PaCO₂/R)

PIO₂ has been calculated in previous question as 42 mmHg. Therefore, P_AO₂ = 42 – (40/1) = 2 mmHg

Question 32

In which of the following chemical forms most of CO₂ is transported in the blood from the body cells to the lungs?

(a) Dissolved CO2
(b) Carbonic acid
(c) Carbamino compounds
(d) Carboxy hemoglobin
(e) Bicarbonate

Answer 32

Explanation: E is correct: More than 2/3 of the CO2 is transported in blood in form of HCO3-.

Question 33

Blood gases from a premature baby with labored breathing (intercostal retractions) and x-ray evidence of atelectasis (lung collapse) were PaO₂ = 50 mm Hg; PaCO₂ = 36 mm Hg; pH = 7.28; arterial sat. = 60%. Barometric pressure was 747 mm Hg. What is most likely the cause of low arterial oxygen saturation of this baby?

(a) Fetal hemoglobin
(b) High altitude
(c) Diffusion limitation
(d) Hypoventilation

Answer 33

Explanation: C is correct: Premature baby has surfactant deficiency. Surfactant normally prevents water accumulation in alveoli. Therefore, lung edema is likely to occur with surfactant deficiency. In addition a reduction of surface area may also result from surfactant deficiency due to an increased recoiling force of the lung. Both lung edema and surface area reduction could cause diffusion limitation and thus produce hypoxia. The other given choices cannot be the cause of hypoxia in this patient. Respiratory acidosis and hypoventilation do not exist by this patient, because PaCO2 is lower than normal. High altitude is wrong, because PB is 747 mmHg and fetal hemoglobin cannot produce hypoxia.

Question 34

Healthy people can increase their ventilation either voluntarily or in response to stimuli like hypoxia, hypercapnia, exercise, hyperthermia and acidic pH. Which of the following mechanisms is capable of producing the greatest minute ventilation?

(a) A decreased PO2 and increased PCO2
(b) Hyperthermia
(c) Voluntary effect
(d) Exercise
(e) Hypotension

Answer 34

Explanation: C is correct: Among all stimuli of breathing, the Voluntary increase of ventilation is the most powerful mechanism.

Question 35

Total Pulmonary vascular resistance (PVR) is decreased

(a) At high lung volume
(b) With decreased cardiac output
(c) By breathing low oxygen
(d) With increased pulmonary artery pressure
(e) At low lung volume

Answer 35

Explanation: D is correct: An increase in pulmonary artery pressure will cause widening of open vessels and recruitment of some pulmonary capillaries that were closed at the normal pulmonary pressure. Both mechanisms (widening and recruitment of the vessels) reduces the total pulmonary vascular resistance.

Question 36

High altitude residency sometimes result in a right heart failure (cor pulmonale). What is the cause of this type of right heart failure?

(a) Prolonged inhibition of angiotensis converting enzyme (ACE)
(b) Respiratory alkalosis resulting from increased ventilation
(c) Failure of medullary cardiac center
(d) Pulmonary hypertension caused by alveolar hypoxia
(e) Increased preload on the right ventricle

Answer 36

Explanation: D is correct: A person at high altitude becomes hypoxic (Barometric pressure is decreased causing PIO2 and PAO2 to be reduced) and alveolar hypoxia produces pulmonary vasoconstriction. The right ventricle must eject the blood against a higher pressure and in the long run it may ends up with right heart failure.

Question 37

Which of the following correctly describe the properties for transport of O₂ and CO₂?

(a) The presence of carbon dioxide decreases the P50 for O₂
(b) Equal amounts of oxygen and carbon dioxide can be carried in 100 mL of blood
(c) The presence of oxygen increases carbon dioxide content in the blood
(d) The slopes of the oxygen and carbon dioxide content curves are similar
(e) Most of the O₂ and CO₂ are transported by the red blood cell

Answer 37

Explanation: E is correct: Most of O2 is bound with hemoglobin within erythrocytes. Because of high concentration of Hb in erythrocytes, the H+ buffering capacity of Erythrocytes is high as well. High Buffering capacity augments the formation of HCO3- from CO2 in erythrocytes.