wk6: respiratory mechanics

A collection of flashcards covering key terms and concepts related to pulmonary ventilation.

Definition of respiratory mechanics

The physical forces, pressures, and flow dynamics governing the movement of air into and out of the lungs.

What are the three processes of external respiration?

Pulmonary ventilation, gas exchange and gas transport.

What is external respiration

Exchange of oxygen and carbon dioxide between air and interstitial fluid.

What is internal respiration?

Exchange of oxygen and carbon dioxide between the interstitial fluid and cells

What is pulmonary ventilation (external respiration)

Air flow in and out of the lungs, driven by a pressure gradient.

What are the major mechanisms that drive pulmonary ventilation?

Atmospheric pressure, intrapulmonary or intra-alveolar pressure and intrapleural pressure.

What effect does atmospheric pressure have on pulmonary ventilation?

If the pressure of air outside the body is greater than in the lungs, air will flow in and vice versa.

What effect does intrapulmonary or intra-alveolar pressure have on pulmonary ventilation?

Governed by Boyle’s law, the pressure inside the alveoli fluctuates relative to atmospheric pressure, which drives air flow.

What does Boyle’s law propose?

Pressure and volume are inversely related at constant temperature, as volume increased, pressure decreases.

What effect does intrapleural pressure have on pulmonary ventilation?

Within the pleural cavity, air pressure is lower than atmospheric and intrapulmonary pressures, creating a suction force that keeps the lungs adhered to and expanding with the chest wall.

What occurs during gas exchange in external respiration?

Diffusion of gases between the alveolar air and blood in the capillaries.

What occurs during gas exchange in internal respiration?

Diffusion of gases between blood and tissues.

In relation to external respiration, what is gas transport?

Movement of gases between the blood in alveolar capillaries and capillaries in other tissues.

What is the pathway of gas exchnage in the respiratory system?

Air enters lungs, gases are diffused between alveoli and blood (external respiration), gases are transported in blood, then diffused through interstitial fluid, then gas is diffused between blood and tissues (internal respiration).

What is the interstitial fluid?

Fluid that fills spaces between cells.

What are the mechanisms involved in inhalation during quiet breathing?

The diaphragm and external intercostal muscles contract, leading to increased volume and decreased pressure in the thoracic cavity and lungs (Boyle’s law).

What are the mechanisms involved in exhalation during quiet breathing?

The diaphragm and external intercostal muscles relax, chest wall and lungs recoil, causing the volume inside the lungs to decrease, whilst pressure increases.

What are the four factors that affect pulmonary ventilation

Lung compliance (expandability), elasticity (recoil), surface tension of alveolar fluid and airway resistance.

What does lung compliance affect?

How much effort or force is required to deform/expand the lung.

What does lung elastance/elasticity affect?

How readily the lungs rebound after being stretched (the inverse of compliance).

How does the surface tension of alveolar fluid affect pulmonary ventilation?

Surfactant decreases the surface tension of alveolar fluid, enhancing lung compliance and decreasing elastance.

What is surfactant?

A mixture of phospholipids and proteins produced by type II alveolar cells that coat the inner surface of the alveoli.

How does airway resistance affect pulmonary ventilation?

Air flow is primarily dependent on the diameter of the bronchioles. Air flow is inversely proportional to airway resistance.

What are the four lung volumes?

Tidal, inspiratory reserve, expiratory reserve, and residual volume.

Tidal Volume (TV)

The amount of air moved in or out during a single breath.

Inspiratory Reserve Volume (IRV)

The additional air that can be inhaled after a normal inhalation.

Expiratory Reserve Volume (ERV)

The additional air that can be exhaled after a normal exhalation.

Residual Volume (RV)

The air remaining in the lungs after a maximal exhalation, which prevents lung collapse.

What are the 4 lung capacities

Inspiratory, functional residual, vital and total lung capacity

Inspiratory Capacity

The maximum volume of air that can be inspired at the end of a normal quiet expiration (tidal volume and inspiratory reserve volume).

Functional residual capacity

Volume of air in lungs at the end of normal passive expiration

Vital capacity

The maximum volume of air that can be moved out during a single breath following maximal inspiration

Total Lung Capacity (TLC)

The maximum volume of air the lungs can hold.