Lung Volume and Compliance Quiz
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Questions and Answers

What happens to lung compliance in interstitial pulmonary fibrosis?

  • Compliance increases, requiring less inflation pressure
  • Compliance decreases, resulting in a steeper pressure-volume curve (correct)
  • Compliance decreases, leading to a downward shift in the compliance curve (correct)
  • Compliance remains unchanged during inflation and deflation

    • Which of the following conditions is associated with increased lung compliance?

  • Restrictive lung disease
  • Pulmonary congestion
  • Emphysema (correct)
  • Asthma

    • How does the pressure-volume curve behave during inhalation compared to exhalation?

  • The curve flattens during inhalation
  • The volume at any pressure is the same in both phases
  • The curve shows hysteresis, with lower volume during inhalation (correct)
  • The curve is steeper during exhalation

    • What is the impact of a supine position on lung compliance?

    <p>Decreases compliance by shifting the curve downward and to the right</p> Signup and view all the answers

    What does an upward shift in the compliance curve indicate?

    <p>Increased lung compliance allowing for easier inflation</p> Signup and view all the answers

    During normal breathing, what factor primarily contributes to the hysteresis observed in lung compliance?

    <p>Differences between inspiratory and expiratory lung volumes</p> Signup and view all the answers

    Which measurement expresses normal pulmonary compliance?

    <p>0.1 Liter/cmH2O</p> Signup and view all the answers

    How does the pressure-volume curve of a stiffer lung differ from a more compliant lung?

    <p>It shifts to the right indicating decreased volume for the same pressure</p> Signup and view all the answers

    What role does surfactant play in small alveoli compared to large alveoli?

    <p>It lowers surface tension in small alveoli more significantly than in large alveoli.</p> Signup and view all the answers

    Which factor contributes to lung compliance in infants with IRDS?

    <p>Use of continuous positive airway pressure (CPAP) enhancing compliance.</p> Signup and view all the answers

    What characterizes hysteresis in lung compliance?

    <p>There is a difference in lung volume at the same pressure during inflation and deflation.</p> Signup and view all the answers

    What is the primary function of tubular myelin in alveoli?

    <p>To generate phospholipids for a monolayer at the air-liquid interface.</p> Signup and view all the answers

    Which intervention is effective in improving morbidity and mortality in infants with IRDS?

    <p>Administration of antenatal steroids.</p> Signup and view all the answers

    What primarily contributes to the elastic property of the lung?

    <p>Elastin and collagen fibers</p> Signup and view all the answers

    Which component contributes the most elastic force in the lungs?

    <p>Surface tension of fluid lining alveoli</p> Signup and view all the answers

    Lung compliance is defined as:

    <p>The ability of the lung to expand per unit pressure increase</p> Signup and view all the answers

    What is the total compliance value for both lungs together in a normal adult?

    <p>200 ml/cm of H2O</p> Signup and view all the answers

    Which statement about tissue elastic forces is correct?

    <p>They account for 1/3 of total lung elasticity.</p> Signup and view all the answers

    The compliance of the lungs is generally greater than that of the lungs and thoracic cage combined because:

    <p>The thoracic cage restricts lung expansion.</p> Signup and view all the answers

    What does the area contained in the hysteresis loop of a pressure-volume curve represent?

    <p>Work of breathing for the cycle</p> Signup and view all the answers

    What does a compliance value of 0.13 L/cm of H2O indicate?

    <p>The stretchability of both lungs and chest wall</p> Signup and view all the answers

    Inspiratory and expiratory compliance curves demonstrate:

    <p>Variations in the compliance with different lung volumes</p> Signup and view all the answers

    What is the primary role of surfactant in the alveoli?

    <p>To stabilize alveoli of different radii.</p> Signup and view all the answers

    How does surfactant affect lung compliance?

    <p>It increases lung compliance by reducing surface tension.</p> Signup and view all the answers

    What happens to alveoli during expiration without sufficient surfactant?

    <p>They collapse and merge into larger alveoli.</p> Signup and view all the answers

    How does surfactant prevent pulmonary edema?

    <p>By lowering the surface tension of alveoli.</p> Signup and view all the answers

    According to Laplace's Law, what effect does a smaller radius have on pressure in the alveoli?

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

    What contributes to the immune function of alveolar surfactant?

    <p>Regulating lung inflammation.</p> Signup and view all the answers

    What is the composition of surfactant?

    <p>A mixture of lipids and proteins.</p> Signup and view all the answers

    What is the effect of increased surfactant concentration in decreasing alveolar size?

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

    What role does surfactant play during the change in volume of the lungs?

    <p>It reduces surface tension, allowing for easier lung expansion.</p> Signup and view all the answers

    What does pulmonary compliance refer to?

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

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

    <p>To lower surface tension and prevent alveolar collapse</p> Signup and view all the answers

    Which factor is NOT a determinant of lung compliance?

    <p>Airway resistance</p> Signup and view all the answers

    Hysteresis in lung compliance refers to what phenomenon?

    <p>Different compliance during inflation and deflation phases</p> Signup and view all the answers

    If lung compliance is reduced, what might be the primary consequence?

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

    What shape do the pressure-volume curves of compliant lungs generally exhibit?

    <p>S-shaped</p> Signup and view all the answers

    What role do elastic fibers within the lung parenchyma play in lung compliance?

    <p>They enhance the stability of the alveoli</p> Signup and view all the answers

    Which pleural recess is considered the most dependent part of the pleural sac?

    <p>Costo-diaphragmatic recess</p> Signup and view all the answers

    During deep inspiration, which structure provides reserve space to accommodate lung expansion?

    <p>Pleural recesses</p> Signup and view all the answers

    What layers compose the pleura surrounding the lungs?

    <p>Visceral and parietal layers</p> Signup and view all the answers

    Which type of pleura covers the thoracic surface of the diaphragm?

    <p>Diaphragmatic pleura</p> Signup and view all the answers

    Which type of pleura is responsible for lining the inner surface of the ribs and sternum?

    <p>Costal pleura</p> Signup and view all the answers

    What term is used to describe the measure of expansibility and distensibility of the lungs?

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

    How does the costo-diaphragmatic recess function during full inspiration?

    <p>It allows for lung expansion.</p> Signup and view all the answers

    Which layer of pleura is inseparable from the lung tissue itself?

    <p>Visceral pleura</p> Signup and view all the answers

    What is the location of the costal pleura in relation to the thoracic cavity?

    <p>Lines the inner surface of the thorax</p> Signup and view all the answers

    Which pleural recess is situated between costal and mediastinal pleurae?

    <p>Costo-mediastinal recess</p> Signup and view all the answers

    What physiological role does the pulmonary surfactant play concerning surface tension?

    <p>Stabilizes alveoli during breathing</p> Signup and view all the answers

    In which recess of the pleura is fluid most likely to collect first when present?

    <p>Costo-diaphragmatic recess</p> Signup and view all the answers

    What role does tubular myelin play in alveoli?

    <p>It organizes surfactant phospholipids into a complex lattice.</p> Signup and view all the answers

    Which factor is most crucial for the survival of premature infants suffering from IRDS?

    <p>Administration of antenatal steroids.</p> Signup and view all the answers

    How is most surfactant managed after its initial role in reducing surface tension?

    <p>It is recycled back into type II cells via vesicles.</p> Signup and view all the answers

    What is a significant consequence of low surfactant levels in the lungs of premature infants?

    <p>Higher tendency for alveoli to collapse.</p> Signup and view all the answers

    What is the initial process for surfactant formation within the lungs?

    <p>Synthesis from precursors in the endoplasmic reticulum.</p> Signup and view all the answers

    What fraction of the total lung elasticity is represented by tissue elastic forces?

    <p>1/3</p> Signup and view all the answers

    What is the compliance value of the lungs alone per unit change in airway/alveolar pressure?

    <p>0.20 L/cm of H2O</p> Signup and view all the answers

    How much air do the lungs expand for each unit increase in transpulmonary pressure in a normal adult?

    <p>200 ml</p> Signup and view all the answers

    What primarily contributes to the elastic property of the thoracic cage?

    <p>Elastic nature of muscles, ribs, and tendons</p> Signup and view all the answers

    What does the area contained in the work of breathing loop represent?

    <p>The total work of breathing for the cycle</p> Signup and view all the answers

    What is the change in lung volume per unit change in transpulmonary pressure for the lungs and chest wall combined?

    <p>0.13 L/cm of H2O</p> Signup and view all the answers

    Which statement best describes the relationship between lung compliance and the thoracic cage?

    <p>Lung compliance is generally greater than that of the thoracic cage combined.</p> Signup and view all the answers

    Which curve is used to describe the inspiratory compliance behavior of the lungs?

    <p>Inspiratory compliance curve</p> Signup and view all the answers

    What primarily dictates the elastic forces acting within the alveoli?

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

    What does lung compliance reflect about the lungs?

    <p>The stretchability and expandability of the lungs</p> Signup and view all the answers

    Which of the following conditions is most likely to decrease lung compliance?

    <p>Interstitial pulmonary fibrosis</p> Signup and view all the answers

    What can be inferred about a lung with a compliance value of 0.05 Liter/cmH2O?

    <p>The lung is classified as having low compliance.</p> Signup and view all the answers

    Which description best fits the compliance curve of a lung affected by pulmonary congestion?

    <p>Shifts downward and to the right.</p> Signup and view all the answers

    How does an increase in transpulmonary pressure typically affect lung compliance?

    <p>Increases until a plateau is reached.</p> Signup and view all the answers

    Which factor is NOT associated with increased lung compliance?

    <p>Pulmonary fibrosis</p> Signup and view all the answers

    What does a steeper slope in the pressure-volume curve indicate about lung compliance?

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

    In which scenario would lung compliance be expected to improve?

    <p>In a healthy young adult.</p> Signup and view all the answers

    What physiological principle explains why a stiffer lung requires more inflation pressure?

    <p>Increased transpulmonary pressure.</p> Signup and view all the answers

    Which of the following reflects the impact of a supine position on lung function?

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

    In patients with emphysema, how does the pressure-volume curve typically shift?

    <p>Upward and to the left.</p> Signup and view all the answers

    What is the primary reason surfactant is important in alveoli during expiration?

    <p>It prevents collapse of alveoli due to increased pressure.</p> Signup and view all the answers

    How does the Law of Laplace relate pressure and radius in the context of alveoli?

    <p>A twofold decrease in radius results in a doubling of pressure.</p> Signup and view all the answers

    Which function of alveolar surfactant contributes to preventing pulmonary edema?

    <p>Maintaining a low surface tension to prevent fluid influx.</p> Signup and view all the answers

    What happens to the concentration of surfactant in alveoli as their size decreases?

    <p>The concentration increases to lower surface tension.</p> Signup and view all the answers

    Which of the following correctly describes the composition of surfactant?

    <p>A combination of phospholipids and proteins.</p> Signup and view all the answers

    Why does surfactant enable alveoli of different radii to remain at equilibrium?

    <p>It adjusts surface tension based on alveolar size.</p> Signup and view all the answers

    What occurs if there is a deficiency of surfactant in the alveoli?

    <p>Higher surface tension causing potential collapse.</p> Signup and view all the answers

    Which characteristic of surfactant makes it vital for lung compliance?

    <p>It reduces the centripetal force of surface tension.</p> Signup and view all the answers

    What immediate effect does surfactant have when the alveolus is compressed during expiration?

    <p>It increases the pressure in small alveoli.</p> Signup and view all the answers

    Study Notes

    Lung Volume Changes During Breathing

    • Inspiration: Thoracic cavity expands, lung volume increases, alveolar pressure decreases, pleural pressure decreases, transpulmonary pressure increases
    • Expiration: Thoracic cavity contracts, lung volume decreases, alveolar pressure increases, pleural pressure increases, transpulmonary pressure decreases

    Pulmonary Compliance

    • Compliance: Measures lung and chest recoil
    • It is the slope of the pressure-volume curve
    • During inspiration, lung volume at a given pressure is less than the volume at the same pressure during expiration (hysteresis loop)
    • Normal compliance: 0.1 Liter/cmH2O
    • Low compliance: Needs more inflation pressure
    • High compliance: Needs less inflation pressure
    • Compliance curve shifts downwards and to the right in interstitial pulmonary fibrosis and pulmonary congestion
    • Compliance curve shifts upwards and to the left in emphysema

    Factors Affecting Compliance

    • Compliance decreases (curve shifts downward and to the right): Pulmonary congestion, interstitial pulmonary fibrosis, supine position, restrictive lung disease, pneumothorax, hydrothorax, asthma
    • Compliance increases (curve shifts upward and to the left): Emphysema, old age

    Elastic Properties of Lung and Thoracic Cage

    • Lung: Tissue elastic forces (elastin and collagen fibres of lung parenchyma), elastic forces caused by surface tension of the fluid lining alveoli
    • Thoracic cage: Elastic nature of ribs, muscles and tendons

    Lung Compliance

    • Extent to which the lungs expand for each unit increase in transpulmonary pressure.
    • Total compliance of both lungs together in normal adult: 200 ml of air per cm of water transpulmonary pressure.

    Surface Tension and Alveolar Surfactant

    • Alveoli lined with fluid, creating air-water interface
    • Surface tension of water tends to collapse alveoli
    • Surfactant reduces surface tension, counteracting collapse
    • Surfactant concentration increases as alveoli shrink, stabilizing them.

    Functions of Alveolar Surfactant

    • Stabilization: Allows alveoli of different radii to remain at equilibrium
    • Prevention of collapse: Surfactant minimizes collapse during expiration
    • Prevention of pulmonary edema: Prevents fluid from entering the alveoli
    • Increases lung compliance: Reduces surface tension, making lungs more stretchable
    • Immune function: Regulates lung inflammation and promotes phagocytosis

    Surfactant and Laplace’s Law

    • Laplace’s Law: Pressure = 2T/r (pressure is proportional to surface tension and inversely proportional to radius)
    • Without surfactant, small alveoli would collapse into larger ones
    • Surfactant lowers surface tension in small alveoli, allowing them to co-exist with larger ones

    Formation and Metabolism of Surfactant

    • Surfactant components synthesized in the endoplasmic reticulum, transported through Golgi apparatus, and packaged in lamellar bodies
    • Secreted into alveoli, forming a monolayer that lowers surface tension
    • Surfactant components recycled by type II cells and alveolar macrophages

    Infant Respiratory Distress Syndrome (IRDS)

    • Premature babies often lack surfactant, leading to lung collapse
    • IRDS can be treated with antenatal steroids to enhance pulmonary maturity, continuous positive airway pressure (CPAP) and surfactant replacement therapy.

    Pleural Layers

    • Parietal Pleura: Lines the thoracic cavity, subdivided into costal, diaphragmatic, cervical, and mediastinal pleurae
    • Visceral Pleura: Closely invests the lung
    • Both layers are continuous around lung roots and pulmonary ligaments.

    Pleural Recesses

    • Spaces formed by folds of parietal pleura; act as reserve space for lung expansion
    • Costo-mediastinal recess: Between costal and mediastinal pleurae
    • Costo-diaphragmatic recess: Between lower limit of pleural sac and lower border of lung; most dependent part of pleural sac
    • Functions of Costo-diaphragmatic Recess: Allows lung expansion in full inspiration; collects fluid if pleural effusion occurs.

    Pleura

    • A closed serous sac
    • Contains two layers: Parietal and Visceral
    • Both layers are continuous around lung roots and pulmonary ligaments

    Visceral Pleura

    • Closely invests lung (except hilum and attachment of lung root) and is inseparable from it

    Parietal Pleura

    • Named according to the structures it lines
    • Subdivided into Costal, Diaphragmatic, Cervical, and Mediastinal pleurae

    Costal Pleura

    • Lines the inner surface of the sternum, ribs, costal cartilages, intercostal spaces, and sides of the vertebral bodies

    Diaphragmatic Pleura

    • Covers the thoracic surface of the diaphragm

    Cervical Pleura

    • Covers the apex of the lung and passes downwards and medially to continue with the mediastinal pleura

    Mediastinal Pleura

    • Forms the lateral boundary of the mediastinum and covers the mediastinal surface of the lungs

    Recesses of Pleura

    • Widening of the pleural cavity
    • Folds of the parietal pleura which act as reserve spaces for lungs to expand during deep inspiration

    Costo-Mediastinal Recess

    • Between costal and mediastinal pleurae

    Costo-Diaphragmatic Recess

    • Potential space between lower limit of pleural sac and lower border of corresponding lung

    Costo-Diaphragmatic Recess - Lower Limit of Pleura and Lung

    • At the mid-clavicular, mid-axillary, and scapular lines: 8th, 10th, and 12th ribs respectively
    • Lower border of lung: 6th, 8th, and 10th ribs

    Costo-Diaphragmatic Recess - Functions

    • Allows expansion of lungs in full inspiration
    • Most dependent part of the pleural sac
    • If fluid appears in the pleural sac, it will collect first in the Costo-diaphragmatic recess

    Determinants of Lung Compliance

    • Both lungs and the thoracic cage are viscoelastic structures which can be expanded (stretched)
    • The measure of expansibility/distensibility is known as compliance
    • Lung compliance: 200 ml of air per cm of water transpulmonary pressure in a normal adult
    • Tissue elastic forces represent 1/3 of total lung elasticity
    • Fluid-air surface tension elastic forces in alveoli represent 2/3 of total lung elasticity

    Pulmonary Compliance - Factors Affecting Compliance

    • Decreased compliance (curve shifted downward and to the right): Pulmonary congestion, interstitial pulmonary fibrosis, supine position, restrictive lung disease, pneumothorax, hydrothorax, asthma
    • Increased compliance (curve shifted upward and to the left): Emphysema, old age

    Surface Tension

    • In each alveolus there is an interface between air and water
    • The water molecules at the superficial layer of alveolar fluid are attracted laterally and inwardly
    • This causes the fluid layer to shrink or minimize the liquid-air interface (surface tension)
    • The alveolus tends to collapse
    • Surfactant resists the collapse of the lung

    Action of Surfactant

    • Presence of surfactant reduces surface tension
    • Surfactant content of each alveolus is relatively constant
    • When the alveolus size decreases, the alveolar surfactant concentration increases, which lowers surface tension

    Functions of Alveolar Surfactant

    • Alveolar stabilization: Enables alveoli of different radius to remain at equilibrium
    • Prevention of collapse of alveoli: Alveoli become smaller during expiration
    • Prevent pulmonary edema: Surfactant deficiency causes high surface tension of alveoli, drawing fluids from capillaries leading to pulmonary edema
    • Increases lung compliance: Reduces the centripetal force of surface tension in alveoli and increases stretch ability of lungs
    • Immune function: Regulates lung inflammation, facilitates phagocytosis

    Components of Surfactants

    • Surfactant is a lipid surface-tension-lowering agent
    • It is a mixture of dipalmitoylphosphatidylcholine (DPPC), other lipids, and proteins
    • Law of Laplace: P = 2 T/r (distending pressure equals two times the tension divided by the radius)
    • If alveoli have half the normal radius, the pressures are doubled

    Use of Surfactant

    • Prevents collapse during expiration
    • Preventions pulmonary edema

    Laplace’s Law

    • Relates pressure to (surface) tension and radius: Pressure = 2 T/r
    • Small radius = High pressure
    • Without surfactant small alveoli would empty into bigger alveoli and collapse
    • In presence of surfactant, surface tension is no longer a constant

    Formation of Surfactant

    • Components of surfactant are synthesized from precursors in the endoplasmic reticulum and transported through the Golgi apparatus by multi-vesicular bodies.
    • Components are packaged in lamellar bodies, intracellular storage granules.
    • Secretion (exocytosis) into the liquid lining of the alveolus, surfactant phospholipids are organized into a complex lattice called tubular myelin
    • Tubular myelin is believed to generate the phospholipid that provides material for a monolayer at the air-liquid interface in the alveolus, lowering surface tension

    Metabolism of Surfactant

    • Surfactant phospholipids and proteins are subsequently taken back into type II cells in the form of small vesicles
    • Transported for storage into lamellar bodies for recycling
    • Alveolar macrophages also take up some surfactant in the liquid layer.
    • Phospholipid components of surfactant remain in the alveolar lumen for few hours and taken back into type II cells and are reused 10 times before being degraded

    IRDS (Infant Respiratory Distress Syndrome)

    • Respiratory distress syndrome of the newborn/infant/hyaline membrane disease
    • Surfactant is not usually secreted into the alveoli until 6-7 months (or even later) of gestation
    • Many premature babies have little or no surfactant and their lungs have an extreme tendency to collapse
    • Improvement in morbidity and mortality in infants with IRDS by:
      • Antenatal steroids to enhance pulmonary maturity
      • Appropriate resuscitation - immediate use of continuous positive airway pressure (CPAP)

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    Test your understanding of lung volume changes during breathing and the factors affecting pulmonary compliance. This quiz covers inspiration, expiration, and the compliance curves related to different pulmonary conditions. Explore how various factors influence lung function and pressure relationships.

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