Lesson 4: Respiratory Mechanics

Question 1

the interrelationship among pressure between what is important in ventilation?

Answer 1

interrelationships among pressure inside and outside the lungs are important in ventilation

Question 2

what are the four different pressure considerations important in ventilation?

Answer 2

• atmospheric (barometric) pressure
• alveolar pressure
• pleural pressure
• transpulmonary pressure

Question 3

what drives air in and out of the lungs, ad also drives gas exchange?

Answer 3

the difference in pressures and the changes in the pressures that changes lung volume

Question 4

what is respiratory mechanics by definition?

Answer 4

interrelationships among pressures inside and outside the lungs that are critical to generate ventilation or movement of air

Question 5

what is atmospheric pressure?

Answer 5

the pressure pushing down on us just in the room
- roughly 760millometres of mercury at sea level (mmHg)

Question 6

*** as we climb a mountain, does atmospheric pressure go up or down?

Answer 6

it goes down

Question 7

what is alveolar pressure?

Answer 7

the pressure inside the alveoli
- the pressure changes depending on what part of respiration you are on

Question 8

what is pleural pressure?

Answer 8

the pressure in the pleural space

Question 9

when we take a little breath in to relax, what is the pleural pressure like compared to the atmosphere?

Answer 9

it is lower
- negative pressure because we are pulling it open

Question 10

what is pleural pressure generally considered?

Answer 10

the intrathoracic pressure representing the pressure in the thoracic cavity (they are typically very close in pressures)

Question 11

what is transpulmonary pressure?

Answer 11

the difference between the alveolar and pleural pressure
- the pressure across the visceral pleura

Question 12

when we take a little breath in to relax, what is the transpulmonary pressure like compared to the atmosphere?

Answer 12

gets bigger

Question 13

what is another name for the transpulmonary pressure?

Answer 13

the recoil pressure

Question 14

what do we have to create when we want to move something like air or fluid?

Answer 14

a pressure gradients

Question 15

the larger the gradient in pressure, the ________ the air is going to move in and out

Answer 15

faster

Question 16

atmospheric pressure diminishes with ____________ altitude as the layer of air above Earth’s surface decreases in thickness

Answer 16

increasing

Question 17

when we talk about pressures, what are we talking about it in relation to?

Answer 17

atmospheric pressure

(ex. We can 0 atmospheric pressure so pleural is -2 from atmospheric) ( used to say pleaural is 758 when atmosphere is 760)

Question 18

what is another name for alveolar pressure?

Answer 18

intrapulmonary pressure

Question 19

when there is no pressure gradient to move along, is there still air flow?

Answer 19

no there is not
- we depend on pressure to move air in and out

Question 20

what is cmH20 a unit of?

Answer 20

pressure

Question 21

how can we measure pleural pressure considering we cannot stick a prob without rupture?

Answer 21

we can estimate by looking at other metrics such as the esophagus because pleural pressure closely approximates the intrathoracic pressure

Question 22

what does transmural pressure mean?

Answer 22

pressure across something

Question 23

what are the two types of transmural pressures?

Answer 23

1. transpulmonary: the difference across the lung wall
2. trans wall pressure: the difference across the chest wall

• we only care about #1

Question 24

what is the equation for the transpulmonary pressure?

Answer 24

alveolar pressure - pleural pressure = transpulmonary pressure

Question 25

what does transpulmonary pressure represent?

Answer 25

the recoil of the lung

Question 26

our alveoli want to collapse but what avoids it?

Answer 26

the pleural pressure

Question 27

when we take a breath in, what happens to our pleural pressure? what about alveolar pressure?

Answer 27

pleural pressure = drops heavily alveolar pressure = drops to a lesser extent transpulmonary pressure = large increase

Question 28

what determines pressure in regards to air?

Answer 28

1. volume (size of "container") 2. temperature: constant for breathing 3. number of molecules #1 is key when we are talking about respiratory

Question 29

what does Boyle's Law state?

Answer 29

P1V1=P2V2 (pressure and volume) - pressure and volume are highly dependent

Question 30

what do we need to do in order to make air move?

Answer 30

pressures need to change

Question 31

what do ventilators do?

Answer 31

they take air and push air in. they create the pressure gradient from the outside

Question 32

what is Poiseuilles Law of Flow?

Answer 32

the magnitude of flow is dependent on the change in pressure as a function o the resistance of the system F = delta P/R essentially: if I want flow, I need a pressure gradient

Question 33

negative flow means?

Answer 33

air is moving into the lung (inspiration)

Question 34

which pressure, during inspiration, pulls the alveoli open such that the alveolar pressure drops a bit?

Answer 34

when we create a negative pleural pressure

Question 35

we change the intrathoracic pressure in inspiration such that?

Answer 35

it drops the alveolar pressure to pull air in

Question 36

review changes in lung volume and alveolar and pleural pressures during inspiration and expiration

Answer 36

wed january 15 lecture