Gaseous Exchange and Perfusion II
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Questions and Answers

What does a normal ventilation-perfusion (V/Q) ratio indicate?

  • Both alveolar ventilation and blood flow are normal. (correct)
  • There is no blood flow to the alveolus.
  • Alveolar ventilation is high while blood flow is low.
  • Alveolar ventilation is low relative to blood flow.

    • What happens when alveolar ventilation (VA) is zero while perfusion (Q) is present?

  • The ventilation-perfusion ratio becomes normal.
  • The ventilation-perfusion ratio is zero. (correct)
  • There is excessive gas exchange in the alveolus.
  • The ventilation-perfusion ratio approaches infinity.

    • What is the likely cause of a zero ventilation-perfusion ratio?

  • Blockage of the airway preventing airflow. (correct)
  • Adequate blood flow with normal ventilation.
  • Normal airway function with low blood flow.
  • Excessive blood flow with normal ventilation.

    • What effect does a pulmonary embolism have on the ventilation-perfusion ratio?

    <p>It stops blood flow while maintaining ventilation.</p> Signup and view all the answers

    What happens to gas exchange when the V/Q ratio is at infinity?

    <p>There is no blood flow to exchange gases.</p> Signup and view all the answers

    Which of the following describes the effect of a blocked airway on gas exchange?

    <p>Leads to zero ventilation and zero gas exchange.</p> Signup and view all the answers

    Which condition is associated with a V/Q ratio approaching zero?

    <p>Blocked airways with normal perfusion.</p> Signup and view all the answers

    What does it indicate when both the V/Q ratio is zero and is at infinity?

    <p>There is no gas exchange taking place.</p> Signup and view all the answers

    What is the primary mission of the academic program described in the document?

    <p>To promote higher standards in medical education and health care</p> Signup and view all the answers

    Which of the following values is NOT mentioned in the document?

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

    What type of shunt is defined as a right-to-left shunt?

    <p>Blood flows from the right side to the left side of the heart</p> Signup and view all the answers

    What is the effect of physiological dead space on pulmonary gas exchange?

    <p>It leads to wasted ventilation and impaired gas exchange</p> Signup and view all the answers

    In the context of the College of Medicine, who is identified as the block coordinator?

    <p>Dr. Shahina Khan</p> Signup and view all the answers

    Which department is Dr. Arif Mohyudin associated with?

    <p>Department of Biomedical Sciences</p> Signup and view all the answers

    What year is noted for the academic block mentioned in the document?

    <p>2022-2023</p> Signup and view all the answers

    Which key theme is addressed in the Gas Exchange and Perfusion II block?

    <p>Defining right-to-left shunt and physiological dead space</p> Signup and view all the answers

    What two main factors determine the PO₂ and PCO₂ in the alveoli?

    <p>Rate of alveolar ventilation and rate of transfer of oxygen and carbon dioxide</p> Signup and view all the answers

    Which statement best describes the ventilation-perfusion ratio?

    <p>It measures the efficiency of gas exchange within the lungs.</p> Signup and view all the answers

    What happens when blood flows through areas of the lungs with little or no ventilation?

    <p>Blood flows but there is poor oxygenation</p> Signup and view all the answers

    Which condition describes having good ventilation but no blood flow?

    <p>Ventilation-perfusion mismatch</p> Signup and view all the answers

    Which is NOT a factor that affects gas diffusion through the respiratory membrane?

    <p>Surface area of the membrane</p> Signup and view all the answers

    What is indicated by a high ventilation-perfusion ratio?

    <p>Poor blood flow or inadequate perfusion</p> Signup and view all the answers

    Which of the following best describes perfusion?

    <p>The circulation of blood through lung tissues</p> Signup and view all the answers

    Which scenario best represents abnormal lung function?

    <p>Good ventilation accompanied by minimal blood flow</p> Signup and view all the answers

    What is the fraction of venous blood passing through pulmonary capillaries that does not become oxygenated called?

    <p>Physiologic shunt</p> Signup and view all the answers

    What percentage of the cardiac output normally flows through bronchial vessels and does not participate in gas exchange?

    <p>2%</p> Signup and view all the answers

    Which of the following statements is true regarding shunted blood?

    <p>Shunted blood results from low oxygen levels in the alveolus.</p> Signup and view all the answers

    What happens to arterial blood when 2% of the cardiac output shunts through bronchial vessels?

    <p>It decreases in oxygen concentration.</p> Signup and view all the answers

    How is the total amount of shunted blood quantified per minute referred to?

    <p>Physiologic shunt</p> Signup and view all the answers

    What effect does an increase in physiologic shunt have on oxygenation of blood?

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

    Under normal conditions, what percentage of the cardiac output is dedicated to oxygen exchange in the pulmonary capillaries?

    <p>98%</p> Signup and view all the answers

    What is the clinical significance of the term 'hypoxia' in relation to shunted blood?

    <p>It indicates a lack of oxygen in the blood.</p> Signup and view all the answers

    What happens to the saturation of hemoglobin when the partial pressure (PO2) decreases from 100 to 90?

    <p>The saturation remains relatively high at about 60%</p> Signup and view all the answers

    How much oxygen is transported in 100 ml of blood that contains 15 grams of hemoglobin?

    <p>20.1 ml of oxygen</p> Signup and view all the answers

    Which hemoglobin variant is found in adults?

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

    What is the primary benefit of the oxygen saturation curve?

    <p>It demonstrates the loading of oxygen to hemoglobin at low PO2 levels.</p> Signup and view all the answers

    During exercise, how does the body's demand for oxygen change?

    <p>The body increases oxygen extraction and delivery to tissues.</p> Signup and view all the answers

    At what saturation level does venous blood typically rest?

    <p>70%</p> Signup and view all the answers

    What is the likely effect of a shift in the oxygen saturation curve for maternal blood?

    <p>Reduced oxygen loading to the fetal circulation</p> Signup and view all the answers

    What saturation is typically associated with arterial blood?

    <p>20 ml</p> Signup and view all the answers

    What is the definition of anatomical dead space?

    <p>The area where air is not oxygenated, such as the trachea.</p> Signup and view all the answers

    What contributes to physiological dead space?

    <p>Wasted ventilation of alveoli combined with anatomical dead space.</p> Signup and view all the answers

    What happens to ventilation in smokers with chronic obstructive lung disease?

    <p>Ventilation is wasted due to alveolar wall destruction and obstruction.</p> Signup and view all the answers

    Which condition results in a VA/Q ratio approaching zero?

    <p>Severe obstruction in small bronchioles.</p> Signup and view all the answers

    Why does chronic obstructive lung disease exhibit both physiological shunt and physiological dead space?

    <p>Due to the combination of damaged alveolar walls and unventilated bronchioles.</p> Signup and view all the answers

    What occurs when alveolar ventilation (Va) equals zero and blood flow (Q) equals one?

    <p>The VA/Q ratio is zero, indicating no effective ventilation.</p> Signup and view all the answers

    What is a major consequence of the destruction of alveolar walls in chronic obstructive lung disease?

    <p>Enlargement of individual alveoli without intact exchange membranes.</p> Signup and view all the answers

    What does physiological dead space encompass?

    <p>Anatomical dead space and unutilized alveolar ventilation.</p> Signup and view all the answers

    Study Notes

    Gas Exchange & Perfusion II Lecture Notes

    • Writer/Reviewer Information:
      • Zainab Adel Alali
      • Zahraa Albarraqi
      • The notes were reviewed by the same team.
      • Notes are numbered 221-222-223

    Academic Year, Title, and CRN

    • Academic Year: 2022-2023
    • Title: Gaseous Exchange and Perfusion II
    • CRN: 15571 (Males) 15583 (Females)
    • Block: 1.3
    • Subject/Discipline: Physiology
    • Expert: Dr. Arif Mohyuddin
    • Block Coordinator: Dr. Shahina Khan

    Vision

    • To become a model in community engagement through excellence and international recognition in medical education, research, and health care.

    Mission

    • To promote higher standards in medical education, health care, research, and community health services

    Values

    • Islamic values
    • Excellence
    • Creativity
    • Compassion
    • Leadership
    • Responsiveness to Community

    Learning Question 2

    • Define right-to-left shunt & physiological dead space (wasted ventilation).
    • What effect does either have on pulmonary gas exchange?

    Effect of Ventilation-Perfusion Ratio on Alveolar Gas Concentration

    • Two factors determine PO₂ and PCO₂ in alveoli:
      • Rate of alveolar ventilation.
      • Rate of transfer of oxygen/carbon dioxide through the respiratory membrane.

    Effect of Ventilation-Perfusion Ratio on Alveolar Gas Concentration Continued

    • Normally, different areas of the lungs are ventilated/perfused.
    • Some areas might be well-ventilated but have little or no blood flow.
    • Other areas can have good blood flow but little or no ventilation.
    • Normal lung function depends on adequate ventilation & perfusion.
    • This issue appears under various conditions:
      • Good ventilation but no perfusion
      • Minimal or no ventilation and perfused well

    Effect of Ventilation-Perfusion Ratio on Alveolar Gas Concentration Continued

    • Ventilation-perfusion (V/Q) ratio is a quantitative concept
    • It helps to understand respiratory exchange in cases of imbalance between alveolar ventilation and blood flow.
    • When the ventilation and perfusion in the alveolus is normal, the V/Q is also normal.
    • When ventilation in alveoli is zero and perfusion is present the V/Q is zero.
    • When perfusion of the alveoli is zero and ventilation is present then V/Q is infinity.

    Effect of Ventilation-Perfusion Ratio on Alveolar Gas Concentration Continued

    • At either zero or infinity ratio, there is no gas exchange through the respiratory membrane in the affected alveoli.
    • This explains the significance of the V/Q ratio.
    • The respiratory consequences of these extremes will be explained later.

    Concept of Physiological Shunt (When VA/Q is Below Normal)

    • VA/Q diagram explains the normal PO2 and PCO2.

    Normal PO2-PCO2, VA/Q Diagram

    • 3 different points in the VA/Q diagram (V = 0, V/Q = Normal, and V/Q equals infinity) are explained with PO2 and PCO2 values

    V/Q Ratio

    • V/Q ratio = 0 (No Ventilation): fresh air does not enter the alveoli.
    • Gas levels match venous blood (PO2 = 40 mmHg, PCO2 = 45 mmHg)
    • V/Q ratio = ∞ (No Perfusion): Blood flow to the alveoli is absent.
    • Gas levels match inspired air (PO2 = 149 mmHg, PCO2 = 0 mmHg)
    • Normal Alveolar Air: PO2 = 104 mmHg, PCO2 = 40 mmHg

    "Physiologic Shunt"

    • When VA/Q is below normal, there's insufficient ventilation to fully oxygenate blood flowing through alveolar capillaries.
    • A portion of venous blood passing through the pulmonary capillaries doesn't become oxygenated.
    • This fraction is called shunted blood.
    • Shunted blood leads to less oxygen in the blood (hypoxia).
    • Some additional blood flow exists through bronchial vessels rather than through alveolar capillaries, normally about 2% of cardiac output (unoxygenated, shunted blood).

    "Physiologic Dead Space"

    • Explains the concept when VA/Q is above normal.
    • Air in the alveoli isn't exchanged due to insufficient blood flow to carry the oxygen. This air is considered 'wasted.'
    • This is due to inadequate blood flow to carry the oxygen.
    • The sum of these two types of wasted ventilation is called physiological dead space.

    "Physiologic Dead Space" Continued

    • When physiological dead space is substantial, much of the work of ventilation is wasted.
    • This is because much of the inhaled air does not reach the blood.

    Abnormal VA/Q in Chronic Obstructive Lung Disease

    • Smokers often develop bronchial obstruction, eventually leading to severe alveolar air trapping and emphysema.
    • Emphysema damages alveolar walls.
    • Obstruction of small bronchioles results in zero V/Q ratio.
    • Destruction of alveolar walls results in V/Q being greater than normal.
    • These conditions severely decrease the lungs' effectiveness, reducing it sometimes to less than a tenth of normal effectiveness, impairing gas exchange.

    Learning Question 3

    • Describe the relationship between alveolar gas exchange and the arterial blood gas values PCO2 and PO2

    Normal Values

    • Includes data for Alveoli, Arterial Blood, and Mixed Venous Blood. The data is displayed in a table format.
      • PA O2 (mmHg), SaO2
      • PA CO2 (mmHg)
      • HCO3 mE/L
      • pH (Values for different types of blood are displayed)

    Normal PO2-PCO2, VA/Q Diagram

    • Illustrative graph shows relationship of PO₂ in blood and percent hemoglobin saturation.

    Oxyhemoglobin Dissociation Curve

    • Describes the S-shaped oxyhemoglobin dissociation curve.
    • Explains how hemoglobin binds and releases oxygen based on partial pressure.
    • Describes the association and dissociation processes.
    • Saturation values of hemoglobin as PO₂ changes (e.g. 50%, 97%). The graph plots percent hemoglobin saturation vs PO₂ of blood (mm Hg).

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    Gas Exchange & Perfusion II 2024-2025 Lecture Notes PDF

    Description

    This quiz covers key concepts from the Gaseous Exchange and Perfusion II lecture notes, focusing on definitions and physiological implications. Understand important terms such as right-to-left shunt and physiological dead space. Enhance your understanding of gas exchange principles in physiology.

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