Lung Compliance and Function Quiz

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Questions and Answers

What primarily determines the elastic forces of lung tissue?

Smooth muscle fibers

Surfactant production

Connective tissue density

Elastin and collagen fibers (correct)

Which factor is NOT mentioned as affecting lung compliance?

Connective-tissue structure of lungs

Ambient air pressure (correct)

Level of surfactant production

Mobility of the thoracic cage

How does surfactant influence lung compliance?

By reducing surface tension (correct)

By enhancing elastic recoil

By increasing airway resistance

By increasing surface tension

What is the relationship between lung compliance and the work of breathing?

Lower compliance increases work of breathing Signup and view all the answers

Which condition would likely decrease lung compliance?

Lung fibrosis Signup and view all the answers

What is meant by lung compliance?

The lung's ability to stretch and expand Signup and view all the answers

What effect does increased pulmonary venous pressure have on lung compliance?

It decreases lung compliance Signup and view all the answers

Which type of cells are responsible for surfactant production?

Type II alveolar epithelial cells Signup and view all the answers

What is the primary function of surfactant in the alveoli?

To reduce surface tension of the alveolar fluid. Signup and view all the answers

How does compliance differ from elasticity in lung function?

Compliance deals with lung expansion, while elasticity concerns returning to the original shape. Signup and view all the answers

What role does surface tension play in lung function?

It can lead to alveolar collapse during exhalation if uncountered. Signup and view all the answers

What typically happens to alveoli in chronic obstructive pulmonary disease (COPD)?

Alveolar walls progressively degenerate, increasing compliance. Signup and view all the answers

What is a defining factor for the elasticity of lung tissue?

The high content of elastin proteins in the lungs. Signup and view all the answers

What condition may result from insufficient alveolar inflation?

Alveolar edema Signup and view all the answers

What can lead to atelectasis in the lungs?

Unventilated lung regions Signup and view all the answers

What primarily causes surface tension in the lungs?

Attraction between water molecules at the air-fluid interface. Signup and view all the answers

How does surfactant contribute to lung function during exhalation?

It stabilizes the alveoli to prevent collapse Signup and view all the answers

What is the typical value of Tidal Volume (TV) for an average adult?

500 mL Signup and view all the answers

What prevents the lungs from collapsing after maximum exhalation?

Residual Volume (RV) Signup and view all the answers

Which formula correctly represents Total Lung Capacity (TLC)?

TLC = TV + IRV + ERV + RV Signup and view all the answers

What does Vital Capacity (VC) measure in lung function?

Maximum air that can be exhaled after inhalation Signup and view all the answers

What condition are premature infants at risk of due to inadequate surfactant production?

Respiratory distress syndrome (RDS) Signup and view all the answers

Which of the following lung capacities represents air that can be inhaled after a normal tidal exhalation?

Inspiratory Capacity (IC) Signup and view all the answers

What is the typical value of Functional Residual Capacity (FRC)?

2,400 mL Signup and view all the answers

Which of the following statements best describes the Forced Expiratory Volume in the first second (FEV1) in obstructive lung disease?

It is reduced proportionally more than FVC, resulting in FEV1/FVC < 70%. Signup and view all the answers

Which factor does NOT influence Vital Capacity (VC)?

Altitude Signup and view all the answers

What is the primary purpose of spirometry in pulmonary function tests?

To predict the presence of pulmonary dysfunction Signup and view all the answers

How does pregnancy affect lung volume or capacity?

Unchanged or may increase by about 10% Signup and view all the answers

What characterizes anatomic dead space?

It is the volume that does not participate in gas exchange. Signup and view all the answers

Which factors decrease lung capacity in supine position?

Reduced space for lung expansion Signup and view all the answers

What happens to FEV1 and FVC in restrictive lung disease?

Both are reduced, resulting in normal or increased FEV1/FVC. Signup and view all the answers

What is the definition of anatomic dead space?

The volume of air in the conducting airways that does not reach the alveoli. Signup and view all the answers

Which condition can lead to an increase in alveolar dead space?

Pulmonary embolism blocking blood flow to alveoli. Signup and view all the answers

What is the typical volume of anatomic dead space in a healthy adult?

150 mL Signup and view all the answers

If tidal volume (TV) is 500 mL and anatomic dead space is 150 mL, what is the volume that effectively participates in gas exchange?

350 mL Signup and view all the answers

What happens to total ventilation when there is an increase in physiological dead space?

Total ventilation decreases due to less air being exchanged. Signup and view all the answers

What is the formula to calculate total ventilation if tidal volume is 500 mL and there are 15 breaths per minute?

$500 imes 15$ Signup and view all the answers

What occurs if physiological dead space is greater than anatomic dead space?

There is an imbalance of ventilation and perfusion. Signup and view all the answers

What volume represents alveolar ventilation if tidal volume is 500 mL and anatomic dead space is 150 mL, at a rate of 15 breaths per minute?

$5250$ mL/min Signup and view all the answers

Study Notes

Physical Properties of the Lungs

Compliance: Lung compliance, also known as pulmonary compliance, measures the lung's ability to stretch and expand (distensibility of elastic tissue). It's a change in lung volume per change in transpulmonary pressure (DV/DP). The lung is 100 times more distensible than a balloon. Compliance is determined by elastic forces in the lungs.
Elastic Forces: These forces have two components: (1) elastic forces of lung tissue (determined mainly by elastin and collagen fibers in the parenchyma) and (2) elastic forces from surface tension of fluid lining the alveoli.
Surface Tension: Fluid surface tension decreases lung compliance. A lung with low compliance needs more force for breathing, while a lung with high compliance requires less force.
Surfactant: Surfactant, a mixture of lipids and proteins secreted by Type II alveolar epithelial cells (about 10% of alveolar surface area), decreases surface tension in alveoli. It disrupts cohesive forces between water molecules in alveolar fluid, making it easier for alveoli to expand and stay open during inhalation and exhalation. Compressed surfactant phospholipid molecules decrease surface tension to near-zero levels at the end of exhalation.
Mobility of the Thoracic Cage: Any musculoskeletal disease decreases lung compliance.
Compliance Reduction: Compliance reduces when pulmonary venous pressure increases, or alveolar edema occurs due to insufficient alveolar inflation, or the lung remains unventilated (atelectasis), or lung diseases cause fibrosis. Conversely, in chronic obstructive pulmonary disease (e.g. emphysema), alveolar walls degenerate, increasing compliance.

Lung Volumes and Capacities

Lung Volumes: Measurements of air in the lungs at different stages of the breathing cycle.
Tidal Volume (TV): The amount of air inhaled or exhaled with each breath during normal breathing. Typical value: 500 mL for an average adult.
Expiratory Reserve Volume (ERV): The amount of air that can be exhaled after a normal tidal exhalation. Typical value: 1100 mL.
Residual Volume (RV): The amount of air remaining in the lungs after maximum exhalation, preventing lung collapse. Typical value: 1200 mL.
Lung Capacities: Combinations of two or more lung volumes, giving a broader picture of lung function.
Total Lung Capacity (TLC): The total amount of air the lungs can hold. Formula: TLC = TV + IRV + ERV + RV. Typical value: 6000 mL.
Vital Capacity (VC): The maximum amount of air exhaled after maximum inhalation. Formula: VC = IRV + TV + ERV. Typical value: 4800 mL.
Inspiratory Capacity (IC): The maximum amount of air that can be inhaled after a normal tidal exhalation. Formula: IC = TV + IRV. Typical value: 3600 mL.
Functional Residual Capacity (FRC): The amount of air remaining in the lungs after a normal tidal exhalation. Formula: FRC = ERV + RV. Typical value: 2400 mL.

Pulmonary Function Tests

Pulmonary Function Tests (PFTs): A group of tests measuring how well lungs function, assessing lung volume, capacity, flow, and efficiency of oxygen exchange between lungs and blood. Used to diagnose and monitor conditions like asthma and COPD.
Spirometry: The most common PFT, measuring how much and how quickly air can be breathed in and out.
Spirometer Goals: Predicting pulmonary dysfunction, differentiating obstructive and restrictive lung diseases, assessing disease severity and progression, evaluating treatment response, and assessing lung impairment from occupational hazards.

Measurements Obtained from Spirometer

Forced Expiratory Volume in the First Second (FEV1): The volume of air forcefully exhaled in the first second after a deep breath. Usually >70% of FVC (FEV1/FVC > 70%).
Obstructive Lung Disease: In obstructive conditions (e.g., asthma, COPD), FEV1 is reduced more than FVC, resulting in FEV1/FVC < 70%.
Restrictive Lung Disease: In restrictive conditions (e.g., fibrosis), both FEV1 and FVC are reduced, resulting in a normal or increased FEV1/FVC.

Factors Influencing Vital Capacity (VC):

Physiological: Directly proportional to height, more in males due to greater chest size and muscle power (increased surface area). Decreases with age and in supine position. Affected by strength of respiratory muscles and pregnancy (unchanged or increase by 10%).
Pathological: Disease of respiratory muscles and abdominal conditions (e.g., pain, splinting).

Dead Space

Dead Space: Air in the airways and lungs that does not participate in gas exchange.
Anatomic Dead Space: The volume of air in conducting airways (nose, mouth, trachea, bronchi). Approximately 150 mL in a healthy adult.
Alveolar Dead Space: The volume of air reaching alveoli but not participating in gas exchange due to poor perfusion. Can increase in pathological conditions.
Total Dead Space: The sum of anatomic and alveolar dead space. An increase indicates respiratory system inefficiency. In healthy individuals, physiologic dead space equals anatomic dead space.

Ventilation

Total Ventilation: Total volume of gas leaving the lungs per unit time.
Alveolar Ventilation: Volume of gas reaching the respiratory airways. Not all total ventilation reaches the alveoli. Anatomic dead space (150ml of tidal volume) is not involved in gas exchange.

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Description

Test your knowledge on lung compliance, elasticity, and the role of surfactant in lung function. This quiz covers key factors affecting lung mechanics and common respiratory conditions. Understand the implications of these concepts for respiratory health.