3.1 Levitzky Ch 6
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Questions and Answers

Which gas has the fastest equilibration between alveolar partial pressure and partial pressure in blood?

  • Carbon monoxide
  • Nitrous oxide (correct)
  • Oxygen
  • None of the above

    • What factor limits the diffusion of carbon monoxide from the alveolus to the pulmonary capillary blood?

  • Rapid equilibration with the alveolar partial pressure
  • Surface area and thickness of the barrier
  • Diffusivity in the barrier (correct)
  • Chemical combination with hemoglobin

    • Why does the partial pressure of carbon monoxide in the pulmonary capillary blood not match that of the alveoli?

  • High inspired concentration of carbon monoxide
  • Chemical combination with hemoglobin (correct)
  • Rapid equilibration with the alveolar partial pressure
  • Low diffusivity in the alveolar-capillary barrier

    • Why is carbon monoxide transfer considered diffusion-limited rather than perfusion-limited?

    <p>Chemical combination with hemoglobin</p> Signup and view all the answers

    At resting cardiac outputs, how long does blood typically spend in a pulmonary capillary?

    <p>0.75 second</p> Signup and view all the answers

    What contributes to the decrease in velocity of bulk flow as air approaches the alveoli during inspiration?

    <p>Increased total cross-sectional area in distal airways</p> Signup and view all the answers

    How does oxygen primarily move through the alveoli according to its partial pressure gradient?

    <p>By diffusion</p> Signup and view all the answers

    According to Henry's law, what determines the amount of a gas absorbed by a liquid with which it does not chemically combine?

    <p>The partial pressure of the gas and its solubility in the liquid</p> Signup and view all the answers

    What determines the rate of diffusion of gas through the alveolar-capillary barrier according to Fick's law for diffusion?

    <p>Surface area, diffusivity, and barrier thickness</p> Signup and view all the answers

    How does an increase in capillaries recruited during exercise impact the surface area available for diffusion?

    <p>Increases surface area for diffusion</p> Signup and view all the answers

    What factor can increase the transfer of nitrous oxide from a particular alveolus to its pulmonary capillary?

    <p>Increasing the time blood stays in the pulmonary capillary</p> Signup and view all the answers

    At what point does oxygen transfer from alveolus to pulmonary capillary become perfusion-limited?

    <p>When the partial pressure of oxygen in the blood rises to that in the alveolus</p> Signup and view all the answers

    What happens to the partial pressure gradient across the alveolar-capillary membrane when oxygen is chemically bound to hemoglobin?

    <p>It becomes negligible</p> Signup and view all the answers

    What effect does exercise have on the time blood spends in the pulmonary capillary?

    <p>It decreases, allowing less time for gas exchange</p> Signup and view all the answers

    How does increasing cardiac output affect nitrous oxide transfer in pulmonary capillaries?

    <p>It increases nitrous oxide transfer by decreasing equilibration time</p> Signup and view all the answers

    What is the relationship between solubility and diffusion through the alveolar-capillary barrier?

    <p>Directly proportional</p> Signup and view all the answers

    According to Graham's law, what is the relative rate of diffusion of two gases inversely proportional to?

    <p>The square roots of their molecular weights</p> Signup and view all the answers

    Which factor is NOT a component that limits the movement of a gas through the alveolar-capillary barrier according to Fick's law for diffusion?

    <p>Molecular weight of the gas</p> Signup and view all the answers

    Why is the partial pressure gradient of a gas across the barrier considered a major determinant of its rate of diffusion?

    <p>It determines how gases move from mixed venous blood to pulmonary capillaries</p> Signup and view all the answers

    What is the main difference between gas movement by diffusion and gas movement through conducting airways?

    <p>Gas movement by diffusion is based on partial pressure gradients, while gas movement through conducting airways is based on differences in total pressure.</p> Signup and view all the answers

    Why does gas transfer during diffusion depend on temperature?

    <p>Temperature influences molecular movement, with higher temperatures leading to increased molecular movement.</p> Signup and view all the answers

    How does gas transfer occur in a static situation?

    <p>Gas transfer stops as equilibrium is reached, and no partial pressure differences exist for any gases.</p> Signup and view all the answers

    Why does the net movement of gas during diffusion depend on the partial pressure difference?

    <p>The area with higher partial pressure has proportionately more random 'departures', leading to a net movement towards lower partial pressure.</p> Signup and view all the answers

    How does Fick's Law describe oxygen transfer into the alveoli?

    <p>Oxygen is brought into the alveoli by bulk flow through the conducting airways.</p> Signup and view all the answers

    What contributes to the increased total oxygen transfer during exercise?

    <p>Recruitment of previously unperfused capillaries</p> Signup and view all the answers

    When might a person experience diffusion limitation of oxygen transfer?

    <p>During normal rest with an extremely abnormal alveolar-capillary barrier</p> Signup and view all the answers

    What sets the upper limit for the end-capillary blood PO2?

    <p>Low alveolar PO2</p> Signup and view all the answers

    In a normal person, why is carbon dioxide transfer typically perfusion-limited?

    <p>Normal partial pressure gradient for carbon dioxide</p> Signup and view all the answers

    What is the diffusing capacity of the lung?

    <p>The rate of gas uptake per unit pressure gradient</p> Signup and view all the answers

    What does the diffusing capacity of the lung depend on?

    <p>Both diffusing capacity of the membrane and reaction with hemoglobin</p> Signup and view all the answers

    Why is carbon monoxide most frequently used in determinations of the diffusing capacity?

    <p>Its mean pulmonary capillary partial pressure is virtually zero at nonlethal alveolar partial pressures</p> Signup and view all the answers

    What happens to the DLCO in conditions causing interstitial or alveolar fibrosis?

    <p>It decreases</p> Signup and view all the answers

    Which conditions lead to a decrease in the surface area available for diffusion?

    <p>Emphysema and tumors</p> Signup and view all the answers

    What happens to the DLCO in conditions leading to ventilation-perfusion mismatch?

    <p>It decreases</p> Signup and view all the answers

    What does DM represent in determining the diffusing capacity of the lung?

    <p>Diffusing capacity of the membrane</p> Signup and view all the answers

    The diffusing capacity of the lung is solely determined by the diffusing capacity of the membrane, DM.

    <p>False</p> Signup and view all the answers

    Carbon monoxide diffusion is considered perfusion-limited rather than diffusion-limited.

    <p>False</p> Signup and view all the answers

    The DLCO decreases in conditions associated with decreased surface area available for diffusion, such as emphysema.

    <p>True</p> Signup and view all the answers

    Ventilation-perfusion mismatch can lead to an increase in the surface area available for diffusion.

    <p>False</p> Signup and view all the answers

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