Respiratory Mechanics: Lecture 4

Question 1

What is the pleural space?

Answer 1

sack filled with intrapleural fluid

Question 2

When the pleural space expands what is the sign of the pressure inside, positive or negative?

Answer 2

negative

Question 3

What is respiratory mechanics? Definition

Answer 3

interrelationships among pressures inside and outside the lungs are important in ventilation (aka movement of air)

Question 4

What are the 4 different pressures we need to take into consideration?

Answer 4

1. Atmospheric (barometric) pressure
2. Alveolar pressure
3. Pleural pressure
4. Transpulmonary pressure

Question 5

What is Atmospheric pressure?

Answer 5

• pressure pushing down on us from in the room
• 760mmHg

Question 6

What is Alveolar pressure?

Answer 6

• pressure inside the alveoli

Question 7

What is Pleural pressure?

Answer 7

• pressure inside the pleural space

Question 8

What is Transpulmonary pressure?

Answer 8

• equals the difference between the alveolar and the pleural pressure
• pressure across the visceral pleura

Question 9

Will the atmospheric pressure go up or down when climbing a mountain?

Answer 9

• higher up lower pressure

Question 10

Will the atmospheric pressure go up or down when getting to sea level?

Answer 10

• closer to sea level the higher the pressure

Question 11

What is the intrathoracic pressure representing?

Answer 11

• pleural pressure
• pressure in this thoracic cavity

Question 12

When we take a breath in what is happening to all these different pressures?

Answer 12

pleural pressure - low
transpulmonary pressure - higher

Question 13

What is the recoil pressure?

Answer 13

• aka transpulmonary pressure

Question 14

At sea level what is the atmospheric pressure?

Answer 14

760mmHg

Question 15

If the atmospheric and alveolar pressure are equal, is there airflow?

Answer 15

naurrr

Question 16

True or False
Atmospheric pressure will be relatively constant as long as we are walking on Earth in the same general location

Answer 16

True

Question 17

How we move air in and out is dependent on what?

Answer 17

alveolar pressure

Question 18

What will the alveolar pressure need to do to inspire and get air into our lungs?

Answer 18

• alveolar pressure must become lower than the atmospheric pressure to create a gradient, so air can go from high-pressure to low-pressure

Question 19

What will the alveolar pressure need to do to expire and get air out of the lungs?

Answer 19

• alveolar pressure must be higher than the atmospheric pressure

Question 20

What is the unit of pressure in the lungs?

Answer 20

cm per water

Question 21

What leads to a collapsed lung?

Answer 21

when the pleural pressure gets compromised

Question 22

What does transmural refer to?

Answer 22

pressure across something

Question 23

What are the 2 kinds of transmural pressures?

Answer 23

1. Transpulmonary pressure
   - difference across lung wall
2. Transwall pressure
   - difference across the chest wall

Question 24

True or False
The transpulmonary pressure = alveolar pressure - pleural pressure

Answer 24

true

Question 25

What determines pressure? In regards to air

Answer 25

1. Volume - size 2. Temperature *temp can change volume 3. Number of molecules - how many molecules are there

Question 26

What is Boyle's law?

Answer 26

pressure 1 volume 1 = pressure 2 volume 2 - meaning pressure and volume are highly dependent

Question 27

What is Poiseuille's Law of Flow?

Answer 27

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

Question 28

What is the equation of Poiseuille's law of flow?

Answer 28

Flow = change is pressure/resistance of flow F = P/R

Question 29

Negative flow means what?

Answer 29

air is moving into the lung

Question 30

As flow is negative what is happening to the volume?

Answer 30

increases the volume of the lung

Question 31

What happens to the: - change in volume - alveolar, and pleural pressures during inspiration and expiration?

Answer 31

(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