Lung Compliance and Elastic Recoil
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Questions and Answers

What is the relationship between lung compliance and elastance?

  • Compliance is inversely proportional to elastance. (correct)
  • Both are directly proportional to each other.
  • Higher elastance leads to increased compliance.
  • Elastance only affects lung compliance in saline conditions.

    • Which factor does NOT influence lung compliance?

  • Surface tension
  • Elastic fibers
  • Surfactant
  • Airway resistance (correct)

    • What phenomenon causes the tendency of alveoli to collapse?

  • Elastic recoil in the lungs.
  • The attraction between water molecules due to surface tension. (correct)
  • Increased airflow during expiration.
  • High levels of surfactant in the alveoli.

    • How do inspiration and expiration pressure-volume curves differ?

    <p>There is hysteresis due to non-linear resistance.</p> Signup and view all the answers

    Which of the following statements about lung compliance is false?

    <p>Elastance has no effect on lung compliance.</p> Signup and view all the answers

    What is lung compliance primarily a measure of?

    <p>The change in volume per unit change in pressure.</p> Signup and view all the answers

    Which physiological property is primarily associated with lung elastic recoil?

    <p>The ability to rebound during expiration.</p> Signup and view all the answers

    Which of the following conditions is likely to increase lung compliance?

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

    How is the pressure-volume curve of the lungs typically simplified?

    <p>To a single line reflecting elastic properties.</p> Signup and view all the answers

    What percentage of the work of breathing is determined by lung compliance?

    <p>65%.</p> Signup and view all the answers

    Fibrosis affects lung compliance in what manner?

    <p>Makes the lungs stiffer and less compliant.</p> Signup and view all the answers

    What does the transpulmonary pressure indicate during lung expansion?

    <p>The difference between alveolar pressure and pleural pressure.</p> Signup and view all the answers

    Which characteristic of lung compliance is most affected by diseases such as fibrosis or emphysema?

    <p>Elastic resistance.</p> Signup and view all the answers

    What is the primary effect of pulmonary surfactant on alveolar surface tension?

    <p>It acts to lower elastic recoil by reducing surface tension.</p> Signup and view all the answers

    Which condition is characterized by a lack of surfactant, increasing the work needed for lung inflation?

    <p>New-Born Respiratory Distress Syndrome (NRDS)</p> Signup and view all the answers

    What defines the relationship between pressure, surface tension, and the radius of a bubble as per the Law of LaPlace?

    <p>Pressure increases with smaller radius and higher surface tension.</p> Signup and view all the answers

    Which component of pulmonary surfactant significantly contributes to lowering surface tension?

    <p>Dipalmitoyl phosphatidylcholine (DPPC)</p> Signup and view all the answers

    How does pulmonary surfactant affect lung compliance?

    <p>It increases compliance by reducing the elastic recoil forces.</p> Signup and view all the answers

    What is the consequence of insufficient surfactant during lung inflation?

    <p>Increased opening pressure and difficulty in inflation.</p> Signup and view all the answers

    What role does lung elastance play in the context of pulmonary surfactant?

    <p>Surfactant decreases elastance, facilitating easier breathing.</p> Signup and view all the answers

    Which of the following statements regarding the pressure-volume curve is correct?

    <p>A higher slope indicates higher compliance.</p> Signup and view all the answers

    How does increased lung compliance affect elastic recoil?

    <p>It decreases the elastic recoil of the lungs.</p> Signup and view all the answers

    Which factor primarily opposes the inflation of alveoli?

    <p>Alveolar surface tension.</p> Signup and view all the answers

    What phenomenon explains the non-linear relationship of dynamic resistance during breathing?

    <p>Hysteresis.</p> Signup and view all the answers

    Which of the following correctly describes the effect of surfactant on lung compliance?

    <p>Surfactant enhances compliance by reducing surface tension.</p> Signup and view all the answers

    Which of the following phenomena describes the inability of the lungs to behave as a perfect elastic system?

    <p>Hysteresis.</p> Signup and view all the answers

    What primarily determines airway resistance in the respiratory system?

    <p>Diameter of the airway</p> Signup and view all the answers

    Which mechanism contributes to increased airway resistance during an asthma attack?

    <p>Constriction of the bronchioles</p> Signup and view all the answers

    What type of muscle contraction is responsible for bronchoconstriction?

    <p>Smooth muscle contraction by the parasympathetic nervous system</p> Signup and view all the answers

    Which of the following factors would NOT cause increased airway resistance?

    <p>Increased airway diameter</p> Signup and view all the answers

    How can airway resistance be affected by the contraction of smooth muscle?

    <p>It causes bronchoconstriction resulting in decreased airflow</p> Signup and view all the answers

    Which class of medications is used to promote bronchodilation?

    <p>Beta-agonists</p> Signup and view all the answers

    What is a common physiological outcome of airway resistance increasing?

    <p>Increased work of breathing</p> Signup and view all the answers

    Which of the following conditions can result in dynamic small airway closure?

    <p>Inadequate airway dilation</p> Signup and view all the answers

    How does increased lung compliance affect the work of breathing?

    <p>It decreases the work of breathing.</p> Signup and view all the answers

    What is the primary effect of lung fibrosis on lung compliance?

    <p>Decreases lung compliance.</p> Signup and view all the answers

    What role does elastic recoil play during expiration?

    <p>It pushes air out of the lungs.</p> Signup and view all the answers

    Which disease is associated with decreased lung compliance?

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

    What does a pressure-volume curve indicate about lung characteristics?

    <p>Both elastic and airway resistance properties.</p> Signup and view all the answers

    What is the impact of emphysema on lung compliance?

    <p>It increases lung compliance.</p> Signup and view all the answers

    How much of the work of breathing is determined by lung compliance?

    <p>65%</p> Signup and view all the answers

    What is indicated by transpulmonary pressure increasing?

    <p>Lung volume increases.</p> Signup and view all the answers

    What is the main function of pulmonary surfactant in the alveoli?

    <p>To decrease surface tension and increase compliance</p> Signup and view all the answers

    Which of the following is NOT a characteristic of pulmonary surfactant?

    <p>It has a purely hydrophobic nature</p> Signup and view all the answers

    How does a lack of pulmonary surfactant affect lung function in conditions like NRDS?

    <p>Increases the work needed for lung inflation</p> Signup and view all the answers

    According to the Law of LaPlace, what factors determine the magnitude of inward-directed pressure in a bubble?

    <p>Surface tension and the radius of the bubble</p> Signup and view all the answers

    What happens to lung compliance when surfactant levels are decreased, such as in ARDS?

    <p>Lung compliance decreases significantly</p> Signup and view all the answers

    What role do DPPC molecules play in the function of pulmonary surfactant?

    <p>They inhibit the collapse of alveoli</p> Signup and view all the answers

    In conditions like New-Born Respiratory Distress Syndrome (NRDS), the lack of surfactant primarily leads to what physiological issue?

    <p>Increased difficulty in alveolar inflation</p> Signup and view all the answers

    What is the primary composition of pulmonary surfactant?

    <p>A lipoprotein complex of lipids and proteins</p> Signup and view all the answers

    Study Notes

    Lung Compliance

    • Change in volume per unit change in pressure
    • Ability for lungs to be stretched
    • Measure of elastic resistance

    Elastic Recoil (Lung Elasticity)

    • Ability for lungs to rebound
    • Key driving force during expiration

    Pressure-Volume Characteristics

    • Lung characteristics can be simplified by examining them outside of the body
    • As transpulmonary pressure increases, lung volume increases
    • Pressure-volume curve represents both elastic and airway resistance properties of the lungs
    • This is often simplified to a single line

    Compliance and Elastic Recoil: Clinical Implications

    • Many diseases affect lung compliance and it is a useful clinical measure
    • Fibrosis results in a stiffer lung with less compliance
    • Emphysema results in increased lung compliance
    • Compliance accounts for 65% the work of breathing
      • A lung with low compliance requires more work for breathing

    Factors Affecting Lung Compliance

    • Surface tension, elastic fibres, surfactant
    • Compliance is inversely proportional to elastance
      • High compliance = less elastic recoil
      • Low compliance = more elastic recoil

    Alveolar Surface Tension

    • Water molecules are charged and attracted to each other
    • This contributes to the tendency of alveoli to collapse
    • This resists alveolar inflation

    Pulmonary Surfactant

    • Synthesised by type II alveolar cells
    • A lipoprotein complex (mixture of lipids and proteins)
    • Amphilic (both hydrophilic and hydrophobic)
    • Stabilises alveoli and increases lung compliance

    Pathophysiology

    • New-born Respiratory Distress Syndrome (NRDS) - lack of surfactant
    • Acute Respiratory Distress Syndrome (ARDS) - inactivation of surfactant

    ### Airway Resistance

    • Friction between air and airway walls
    • Primarily depends on the airway's diameter
    • Smallest bronchi have the largest total cross-sectional area, so they have the least resistance
    • Medium-sized bronchi have the highest resistance
    • Bronchoconstriction, mucus, fluid and oedema increase airway resistance

    Lung Compliance and Elastic Recoil

    • Compliance is the ability of the lungs to stretch (change in volume per unit change in pressure)
    • Elastic recoil is the ability for lungs to return to their original shape, driven by elastic fibres
    • Pressure-volume curves represent both elastic and airway resistance properties
    • Fibrosis makes lungs stiffer and less compliant
    • Emphysema increases lung compliance
    • The work of breathing is determined by lung compliance. Low compliance requires more work.

    Alveolar Surface Tension

    • Water molecules are charged, leading to a tendency for alveoli to collapse
    • This collapse is resisted by alveolar inflation
    • Pulmonary surfactant, produced by type II alveolar cells, is a lipoprotein complex
    • Surfactant is amphiphilic (hydrophilic and hydrophobic) and stabilises alveoli, increasing lung compliance.
    • In New-Born Respiratory Distress Syndrome (NRDS), there is a lack of surfactant
    • In Acute Respiratory Distress Syndrome (ARDS), surfactant is inactivated.

    ### Importance of Surfactant

    • Surfactant lowers elastic recoil due to surface tension, increasing compliance and decreasing the work of breathing.
    • Without surfactant, the opening pressure of alveoli is high, making it difficult to inflate, and the deflation stability of the lungs decreases.

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    Related Documents

    BIOM2012 Respiratory Physiology L2 PDF

    Description

    This quiz covers the fundamental concepts of lung compliance and elastic recoil, including their definitions and clinical implications. Understand how these properties affect lung function, the pressure-volume characteristics, and the impact of various diseases on lung compliance.

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