Respiratory Mechanics: Lecture 4 Flashcards
What is the pleural space?
sack filled with intrapleural fluid
When the pleural space expands what is the sign of the pressure inside, positive or negative?
negative
What is respiratory mechanics? Definition
interrelationships among pressures inside and outside the lungs are important in ventilation (aka movement of air)
What are the 4 different pressures we need to take into consideration?
- Atmospheric (barometric) pressure
- Alveolar pressure
- Pleural pressure
- Transpulmonary pressure
What is Atmospheric pressure?
- pressure pushing down on us from in the room
- 760mmHg
What is Alveolar pressure?
- pressure inside the alveoli
What is Pleural pressure?
- pressure inside the pleural space
What is Transpulmonary pressure?
- equals the difference between the alveolar and the pleural pressure
- pressure across the visceral pleura
Will the atmospheric pressure go up or down when climbing a mountain?
- higher up lower pressure
Will the atmospheric pressure go up or down when getting to sea level?
- closer to sea level the higher the pressure
What is the intrathoracic pressure representing?
- pleural pressure
- pressure in this thoracic cavity
When we take a breath in what is happening to all these different pressures?
pleural pressure - low
transpulmonary pressure - higher
What is the recoil pressure?
- aka transpulmonary pressure
At sea level what is the atmospheric pressure?
760mmHg
If the atmospheric and alveolar pressure are equal, is there airflow?
naurrr
True or False
Atmospheric pressure will be relatively constant as long as we are walking on Earth in the same general location
True
How we move air in and out is dependent on what?
alveolar pressure
What will the alveolar pressure need to do to inspire and get air into our lungs?
- alveolar pressure must become lower than the atmospheric pressure to create a gradient, so air can go from high-pressure to low-pressure
What will the alveolar pressure need to do to expire and get air out of the lungs?
- alveolar pressure must be higher than the atmospheric pressure
What is the unit of pressure in the lungs?
cm per water
What leads to a collapsed lung?
when the pleural pressure gets compromised
What does transmural refer to?
pressure across something
What are the 2 kinds of transmural pressures?
- Transpulmonary pressure
- difference across lung wall - Transwall pressure
- difference across the chest wall
True or False
The transpulmonary pressure = alveolar pressure - pleural pressure
true
What determines pressure? In regards to air
- Volume
- size - Temperature
*temp can change volume - Number of molecules
- how many molecules are there
What is Boyle’s law?
pressure 1 volume 1 = pressure 2 volume 2
- meaning pressure and volume are highly dependent
What is Poiseuille’s Law of Flow?
the magnitude of flow is dependent on the change in pressure as a function of the resistance of the system
- aka if I want to create flow, I need to create a pressure gradient
What is the equation of Poiseuille’s law of flow?
Flow = change is pressure/resistance of flow
F = P/R
Negative flow means what?
air is moving into the lung
As flow is negative what is happening to the volume?
increases the volume of the lung
What happens to the:
- change in volume
- alveolar, and pleural pressures
during inspiration and expiration?
(i) Before inspiration
- alveolar pressure is 0
- transpulmonary pressure is equal to pleural pressure
(ii) Onset of inspiration
- alveolar pressure decreases (-1) (air goes in)
- pleural pressure decreases
- transpulmonary pressure is on recoil to catch up to pleural pressure
(iii) End of inspiration
- alveolar pressure is 0
- transpulmonary pressure is equal to pleural pressure
(iv) Onset of expiration
- alveolar pressure increases (+1) (air goes out)
- pleural pressure increases
