Mechanics of Pulmonary Ventilation Flashcards
What is Boyles law?
Pressure varies inversely with volume
Why is Boyles law applicable to breathing?
Volume changes within the thoracic cavity create a pressure difference between inside pressure and atmospheric pressure, causing air to flow down it [gradient] in or out of the body
When is inside pressure = to outside pressure?
When there is no breathing. 760mmHg in the lung and outside
How do you get air into the lungs?
Decrease pressure and Increase volume
-greater volume= more space = decrease pressure = air flow in
What allows the increase of volume within the thoracic cavity?
The external intercostal muscles and the Diaphragm
How does the increase in volume in the thoracic cavity happen?
Diaphragm: accounts for 75% of the volume increase
-muscle contracts to pull down the diaphragm
External intercostal muscle: Muscle contracts allowing the thoracic wall (ribs) to expand up and out
How do you get air out of the lungs?
Decrease volume and increase pressure
-decrease volume=less air space=increases pressure =air flows out
What allows the decrease in volume in the thoracic cavity?
Relaxing of the external intercostal muscles and the diaphragm
How does the decrease in volume in the thoracic cavity happen?
Diaphragm gets pulled back up, external intercostal muscle stop contracting
How does inhalation during exercise differ from inhalation at rest?
The more forceful the inhalation causes the diaphragm to pull deeper, creating more volume space
-everything else is the same
How does exhalation during exercise differ from exhalation at rest?
Internal intercostal muscles contract causing the thoracic wall (ribs) to contract down and in (opposite to external intercostal muscles)
Oblique muscles contract
Rectus abdominus contracts (6pack)
-when contracts, causes the organs underneath to shift a little helping to push the diaphragm back up
Do the lungs fully deflate?
Never no matter how hard you exhale
Why don’t the lungs fully deflate?
Due to the intrapleural pressure in the intratpleural space
-757mmHg
Why is having intraleural pressure advantageous?
Lungs don’t collapse even at the end of expiration
Allows for easy expansion of the lung, and there is no resistance against inflation
What happens during a pneumothorax?
When interleura pressure and intrapulmonary pressure become the same pressure by the lung tissue springing back into the chest cavity (causing collapse) and the thoracic wall springing outward
What are the 2 ways in which you can get a pneumothorax?
- Hole in visceral pleura: Gas will flow from high to low until pressures are the same . Causing the lung to collapse
- Hole through chest wall/periatal pleura: Air goes from the environment into the body
- in both cases the intrapleural space goes from only having fluid to having fluid and air
What is lung compliance?
Change in lung volume which is due to change in lung pressure
-how much pressure needed to fill the lung
What is compliance?
The stretchability of the lung
-More compliant the lung, the easier it is to stretch and increase volume during inhalation
What 2 factors influence the compliance of the lung?
Elastic tissue components of the lung
Surface tension inside the alveoli
Why does having too much elastin (elastic tissue) a bad thing?
If you have too much elastin it will become harder for the lung to expand enough, decreasing the compliance
What is surface tension?
Force that develops at the surface of a liquid due to the attraction between water molecules
What is surfactant?
Protein+ phospholipids that make a thin layer over the liquid in the alveoli.
What does surfactant do?
Prevents H2O molecules from sticking together
Prevents lung collapse
Increases compliance
Which group of people dose not having enough surfactant affect?
Premies
-dont have fully developed lungs and can not make enough surfactant to have a normal compliant lung
