Respiratory 13 Flashcards
What forces can affect resistance in airways?
- Inertia of the respiratory system (negligible)
* Friction
What is responsible for 80% of the total airway resistance?
The resistance to airflow that enters the airway
When is airflow resistance sensitive to changes in radius?
When flow is not laminar
What do the different kinds of flow depend on?
the different size of the airways
What are the three types of flows?
- Laminar flow
- Transitional flow
- Turbulent flow
Which airways have laminar flows?
Small airways
How does gas flow in laminar flow?
Gas particles move in a linear fashion
Where does Transitional flow occur?
In larger airways in the bronchial tree
What is the resistance like in transitional flow?
The resistance increases
Where does Turbulent flow occur?
In the larger airways
What kind of airflow occurs in the bronchial tree?
Transitional airflow
Where is Turbulent flow found?
Large airways like the trachea and the larynx
What is the velocity of air in the large airways (trachea, larynx, pharynx)?
It has the highest velocity
What is the correlation between radius and velocity in the airways?
Where the airways are large the velocity is fast
Which airways have the highest resistance to airflow?
The smallest airways
What airflow occurs in small airways?
Laminar flow
Which law is required for laminar flow?
Poiseuille’s law
What is resistance to airflow highly sensitive to?
Changes in airway radius
What does Poiseuille’s law state the viscosity of gas is proportional to?
The length of the tube and is inversely proportional; to the radius raised to the fourth power
What happens if you reduce the radius of an airway?
You dramatically increase the resistance
Where in the respiratory system is the resistance highes?
Medium sized bronchi
Where is resistance the smallest in the airways?
In the respiratory zone
Why is the overall resistance in the terminal bronchioles low?
Because the resistance of the bronchioles is in parallel and is simply the sum of the individual resistances
Which airways play a greater role in determining airflow resistance?
The small airways
What are small airways easily occluded by?
- Smooth muscle contractions
- Edema occurring in the walls of the alveoli and bronchioles
- Mucus collecting in the lumens of bronchioles
