Question 1

Which of the following is not a primary cause of hypoxemia (low oxygen level in the blood)?&#10;A)Anatomical shunt&#10;B)Physiological shunt&#10;C)Low V&#775;/Q&#775;&#10;D)Increased dead space

Accepted Answer

Increased dead space is not a primary cause of hypoxemia. Anatomical shunt, physiological shunt, and low V̇/Q̇ are all primary causes of hypoxemia.

Question 2

In comparison with pulmonary blood flow at rest in the upright position,pulmonary blood flow when upright during exercise in normal individuals is:&#10;A)Distributed more to the bottom of the lung than to the top.&#10;B)Distributed more to the top of the lung than to the bottom.&#10;C)Distributed essentially evenly between the top and the bottom of the lung.&#10;D)Is too highly variable to be determined.

Accepted Answer

During exercise, the increased cardiac output and pulmonary arterial pressure lead to a more uniform distribution of blood flow throughout the lung, from top to bottom, compared to the resting state where gravity causes more blood flow to the bottom of the lungs.

Question 3

If the oxygen consumption is 200 mL/minute and the carbon dioxide production is 140 mL/minute,what is the respiratory quotient?&#10;A)60 mL/minute&#10;B)0.8&#10;C)0.7&#10;D)143 mL/minute

Accepted Answer

The respiratory quotient is the ratio of carbon dioxide production to oxygen consumption. In this case, the respiratory quotient is 140 mL/minute / 200 mL/minute = 0.7.

Question 4

Which of the following does not directly affect the alveolar partial pressure of oxygen? A)Arterial partial pressure of carbon dioxide (Paco₂) B)Atmospheric pressure C)Tidal volume D)Fraction of inspired oxygen E)Oxygen consumption and carbon dioxide production (R)

Accepted Answer

Tidal volume only affects the amount of air that enters and leaves the lungs, but not the partial pressure of oxygen in the alveoli.

Question 5

A twofold increase in the blood flow through a pulmonary arteriole is associated with:&#10;A)No significant change in pulmonary vascular resistance.&#10;B)A twofold increase in pulmonary vascular resistance.&#10;C)A fourfold increase in pulmonary vascular resistance.&#10;D)A 15-fold increase in pulmonary vascular resistance.

Accepted Answer

Pulmonary circulation is unique in its ability to accommodate increased blood flow with minimal changes in resistance, due to the recruitment of additional vessels and distension of existing vessels. This allows for a significant increase in blood flow without a corresponding increase in pulmonary vascular resistance.

Question 6

A patient is admitted to the hospital because of hypoxemia.While the patient breathes ambient air,the arterial partial pressure of oxygen (Pao₂)is 50 mm Hg with an oxygen saturation of 82%.When the patient breathes 100% oxygen through a non-rebreathing mask,the Pao₂ is 83 mm Hg with an oxygen saturation of 92%.The cause of this patient's hypoxemia is probably:

A)A physiological shunt.
B)Low V̇/Q̇.
C)Hypoventilation.
D)Decreased inspired oxygen.

Accepted Answer

A physiological shunt is indicated by the patient's poor response to oxygen therapy, as seen by the relatively low increase in PaO2 despite breathing 100% oxygen. This suggests a portion of the blood bypasses the lungs without gas exchange.

Question 7

When the respiratory rate is 15 breaths per minute,tidal volume is 500 mL,and anatomical dead space volume is 150 mL,what is the minute ventilation?&#10;A)2.25 L/minute&#10;B)5.25 L/minute&#10;C)7.50 L/minute&#10;D)9.75 L/minute

Accepted Answer

Minute ventilation is calculated as the respiratory rate multiplied by the tidal volume. Here, it is 15 breaths per minute * 500 mL = 7500 mL or 7.50 L/minute. The anatomical dead space volume does not affect the calculation of minute ventilation.

Question 8

An individual with early lung disease has a tidal volume of 500 mL.What is the alveolar volume if the dead space doubles and the tidal volume remains the same? (Assume that the normal ratio of dead space ventilation per minute to tidal volume [V_D/V_T] = 0.25.)

A)150 mL
B)250 mL
C)300 mL
D)400 mL

Accepted Answer

With a normal dead space to tidal volume ratio of 0.25, the dead space volume (VD) for a tidal volume (VT) of 500 mL is 125 mL (0.25 * 500 mL). If the dead space doubles, it becomes 250 mL. The alveolar volume (VA) is the portion of the tidal volume that reaches the alveoli and participates in gas exchange. It can be calculated as VA = VT - VD. With the doubled dead space, VA = 500 mL - 250 mL = 250 mL.

Question 9

When alveolar ventilation (V_A)is reduced from 5 L/minute to 2.5 L/minute,the Paco₂ changes from 40 mm Hg to: A)20 mm Hg. B)60 mm Hg. C)80 mm Hg . D)100 mm Hg. E)250 mm Hg.

Accepted Answer

Alveolar ventilation is the amount of air that reaches the alveoli and participates in gas exchange. When alveolar ventilation is reduced, there is less gas exchange occurring, leading to an increase in the partial pressure of carbon dioxide (Paco2) in the blood. This is because carbon dioxide production continues at the same rate, but the removal of carbon dioxide from the body is reduced.

According to the alveolar gas equation, Paco2 is determined by the equation Paco2 = (FiCO2 x (Patm - PH2O)) / VA, where FiCO2 is the fraction of carbon dioxide in inspired air, Patm is the atmospheric pressure, PH2O is the partial pressure of water vapor in inspired air, and VA is alveolar ventilation.

Assuming the other variables remain constant, when alveolar ventilation is reduced from 5 L/minute to 2.5 L/minute, the Paco2 should theoretically double from 40 mm Hg to 80 mm Hg.

Therefore, the best choice is C) 80 mm Hg.

Question 10

The Paco₂ decreases when: A)Alveolar ventilation and CO₂ production are increased and dead space is increased. B)Alveolar ventilation is decreased,CO₂ production is unchanged,and dead space is increased. C)Alveolar ventilation is increased and CO₂ production and dead space are decreased. D)Both alveolar ventilation and CO₂ production are decreased and dead space is increased.

Accepted Answer

Paco2 decreases when alveolar ventilation increases relative to CO2 production. Increased ventilation expels more CO2, and decreased CO2 production and dead space further reduce Paco2.

Deck 23: Ventilation