Lung Mechanics and Respiratory Physiology Quiz

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Questions and Answers

Which of the following best describes the alveolar pressure (PA) at rest?

-5 cmH2O (relative)

755 mmHg (absolute)

760 mmHg (absolute) (correct)

0 mmHg (relative)

What is the main muscle of ventilation?

External intercostals

Internal intercostals

Diaphragm (correct)

Scalenes and SCM

Which muscles are considered accessory muscles of inspiration?

Scalenes and SCM (correct)

Internal intercostals

External intercostals

Abdominal muscles

What is the definition of airway resistance?

The impedance to airflow due to friction and turbulence Signup and view all the answers

Which muscles are considered passive at rest during expiration?

Internal intercostals Signup and view all the answers

What is the pleural pressure at rest, relative to barometric pressure?

-5 cmH2O (relative) Signup and view all the answers

What keeps the lung adhered to the chest wall?

Negative pleural pressure Signup and view all the answers

What causes the lung to collapse inward?

Elastic recoil Signup and view all the answers

What does a pneumothorax cause in the intrapleural space?

Positive pleural pressure Signup and view all the answers

In which condition does emphysema cause a change in compliance?

Increases lung compliance Signup and view all the answers

What leads to a reduced functional residual capacity (FRC) in fibrosis?

Decreased lung compliance Signup and view all the answers

What is responsible for reducing surface tension in the lung?

Surfactant produced by type 1 alveolar cells Signup and view all the answers

What is compliance a measure of?

Change in volume for a change in pressure Signup and view all the answers

What is the role of surfactant in the lungs?

It reduces the surface tension in the lungs Signup and view all the answers

Why are the compliance curves different during expiration and inspiration?

Difference in surface tension Signup and view all the answers

What reduces as lung volume increases, leading to lower compliance at the beginning of expiration?

Elastic recoil pressure Signup and view all the answers

How does lung volume affect surface tension?

Increasing lung volume increases surface tension Signup and view all the answers

According to Poiseuille's law, what has the biggest effect on airway resistance?

Changes in vessel radius Signup and view all the answers

What eliminates the air-fluid interface and significantly reduces surface tension?

Saline filled lung Signup and view all the answers

What factor contributes to increased airway resistance in healthy individuals?

Airway mucus and inflammation Signup and view all the answers

Why is compliance greater in saline inflated lungs?

Elimination of air-fluid interface Signup and view all the answers

Which neurohumoral factor decreases airway resistance by increasing diameter?

Sympathetic nerve stimulation Signup and view all the answers

What is responsible for decreasing surface tension as lung volume increases?

Surfactant Signup and view all the answers

What causes an increase in airway resistance and bronchoconstriction?

Histamine and thromboxane A2 Signup and view all the answers

What contributes to airway resistance across the lung according to Poiseuille's law?

Changes in vessel radius Signup and view all the answers

How does total cross-sectional area change as we progress deeper into the lung?

It increases at each individual tube Signup and view all the answers

What happens to intrapleural pressure during inspiration?

It becomes more negative Signup and view all the answers

What is the role of alveolar pressure (PA) at rest?

It remains zero throughout the breathing cycle Signup and view all the answers

How does elastic recoil pressure change at higher lung volumes?

It increases at higher lung volumes Signup and view all the answers

What happens to alveolar pressure during expiration?

It becomes highly positive to keep the lung open at lower volumes and lower elastic recoil pressures Signup and view all the answers

Study Notes

Respiratory System

Alveolar pressure (PA) at rest is approximately equal to atmospheric pressure.
The main muscle of ventilation is the diaphragm.
Accessory muscles of inspiration include sternocleidomastoid, scalene, and intercostal muscles.

Airway Resistance and Pressure

Airway resistance is the opposition to airflow in the lungs.
Pleural pressure at rest is negative, approximately -5 cmH2O relative to barometric pressure.
The lung is kept adhered to the chest wall by the negative pleural pressure.
A pneumothorax causes air to enter the intrapleural space, leading to lung collapse.
Pleural pressure becomes positive during expiration.

Lung Compliance and Surface Tension

Compliance is a measure of the lung's ability to stretch and expand.
Surfactant reduces surface tension in the lung, allowing for easier expansion.
Compliance curves are different during expiration and inspiration due to changes in surfactant activity.
As lung volume increases, surface tension decreases, leading to increased compliance.

Factors Affecting Airway Resistance and Lung Function

According to Poiseuille's law, airway resistance is most affected by radius, with smaller radii resulting in higher resistance.
Increased airway resistance is contributed to by factors such as bronchoconstriction and decreased diameter.
Neurohumoral factors, such as acetylcholine, increase airway resistance by constricting airways.
Saline-inflated lungs have greater compliance due to the elimination of the air-fluid interface and reduced surface tension.

Changes in Pressure and Volume

During inspiration, intrapleural pressure becomes more negative, and alveolar pressure decreases.
Elastic recoil pressure increases at higher lung volumes, contributing to decreased compliance.
During expiration, alveolar pressure increases, and intrapleural pressure becomes less negative.
Passive muscles during expiration include the diaphragm and intercostal muscles, which relax to allow lung recoil.

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Description

Test your knowledge about static and dynamic lung mechanics and respiratory physiology with this quiz based on resources by Paul McDonough, PhD, Costanzo, L. Physiology, and Cloutier, M. Respiratory Physiology. Learn about pressure gradients, airway resistance, flow limitation, and dynamic airway compression.