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?

Decreases compliance by shifting the curve downward and to the right Signup and view all the answers

What does an upward shift in the compliance curve indicate?

Increased lung compliance allowing for easier inflation Signup and view all the answers

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

Differences between inspiratory and expiratory lung volumes Signup and view all the answers

Which measurement expresses normal pulmonary compliance?

0.1 Liter/cmH2O Signup and view all the answers

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

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

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

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

Which factor contributes to lung compliance in infants with IRDS?

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

What characterizes hysteresis in lung compliance?

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

What is the primary function of tubular myelin in alveoli?

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

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

Administration of antenatal steroids. Signup and view all the answers

What primarily contributes to the elastic property of the lung?

Elastin and collagen fibers Signup and view all the answers

Which component contributes the most elastic force in the lungs?

Surface tension of fluid lining alveoli Signup and view all the answers

Lung compliance is defined as:

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

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

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

Which statement about tissue elastic forces is correct?

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

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

The thoracic cage restricts lung expansion. Signup and view all the answers

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

Work of breathing for the cycle Signup and view all the answers

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

The stretchability of both lungs and chest wall Signup and view all the answers

Inspiratory and expiratory compliance curves demonstrate:

Variations in the compliance with different lung volumes Signup and view all the answers

What is the primary role of surfactant in the alveoli?

To stabilize alveoli of different radii. Signup and view all the answers

How does surfactant affect lung compliance?

It increases lung compliance by reducing surface tension. Signup and view all the answers

What happens to alveoli during expiration without sufficient surfactant?

They collapse and merge into larger alveoli. Signup and view all the answers

How does surfactant prevent pulmonary edema?

By lowering the surface tension of alveoli. Signup and view all the answers

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

Pressure increases with smaller radius. Signup and view all the answers

What contributes to the immune function of alveolar surfactant?

Regulating lung inflammation. Signup and view all the answers

What is the composition of surfactant?

A mixture of lipids and proteins. Signup and view all the answers

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

It decreases surface tension. Signup and view all the answers

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

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

What does pulmonary compliance refer to?

The change in lung volume per unit change in pressure. Signup and view all the answers

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

To lower surface tension and prevent alveolar collapse Signup and view all the answers

Which factor is NOT a determinant of lung compliance?

Airway resistance Signup and view all the answers

Hysteresis in lung compliance refers to what phenomenon?

Different compliance during inflation and deflation phases Signup and view all the answers

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

Increased work of breathing Signup and view all the answers

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

S-shaped Signup and view all the answers

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

They enhance the stability of the alveoli Signup and view all the answers

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

Costo-diaphragmatic recess Signup and view all the answers

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

Pleural recesses Signup and view all the answers

What layers compose the pleura surrounding the lungs?

Visceral and parietal layers Signup and view all the answers

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

Diaphragmatic pleura Signup and view all the answers

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

Costal pleura Signup and view all the answers

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

Compliance Signup and view all the answers

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

It allows for lung expansion. Signup and view all the answers

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

Visceral pleura Signup and view all the answers

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

Lines the inner surface of the thorax Signup and view all the answers

Which pleural recess is situated between costal and mediastinal pleurae?

Costo-mediastinal recess Signup and view all the answers

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

Stabilizes alveoli during breathing Signup and view all the answers

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

Costo-diaphragmatic recess Signup and view all the answers

What role does tubular myelin play in alveoli?

It organizes surfactant phospholipids into a complex lattice. Signup and view all the answers

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

Administration of antenatal steroids. Signup and view all the answers

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

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

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

Higher tendency for alveoli to collapse. Signup and view all the answers

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

Synthesis from precursors in the endoplasmic reticulum. Signup and view all the answers

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

1/3 Signup and view all the answers

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

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

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

200 ml Signup and view all the answers

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

Elastic nature of muscles, ribs, and tendons Signup and view all the answers

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

The total work of breathing for the cycle 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?

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

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

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

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

Inspiratory compliance curve Signup and view all the answers

What primarily dictates the elastic forces acting within the alveoli?

Fluid surface tension Signup and view all the answers

What does lung compliance reflect about the lungs?

The stretchability and expandability of the lungs Signup and view all the answers

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

Interstitial pulmonary fibrosis Signup and view all the answers

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

The lung is classified as having low compliance. Signup and view all the answers

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

Shifts downward and to the right. Signup and view all the answers

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

Increases until a plateau is reached. Signup and view all the answers

Which factor is NOT associated with increased lung compliance?

Pulmonary fibrosis Signup and view all the answers

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

Increased compliance. Signup and view all the answers

In which scenario would lung compliance be expected to improve?

In a healthy young adult. Signup and view all the answers

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

Increased transpulmonary pressure. Signup and view all the answers

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

Decreases lung compliance. Signup and view all the answers

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

Upward and to the left. Signup and view all the answers

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

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

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

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

Which function of alveolar surfactant contributes to preventing pulmonary edema?

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

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

The concentration increases to lower surface tension. Signup and view all the answers

Which of the following correctly describes the composition of surfactant?

A combination of phospholipids and proteins. Signup and view all the answers

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

It adjusts surface tension based on alveolar size. Signup and view all the answers

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

Higher surface tension causing potential collapse. Signup and view all the answers

Which characteristic of surfactant makes it vital for lung compliance?

It reduces the centripetal force of surface tension. Signup and view all the answers

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

It increases the pressure in small alveoli. 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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Description

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.