Lesson 6: Respiratory Compliance and Airways Resistance

Question 1

what is compliance?

Answer 1

the change in lung volume for a given change in transpulmonary pressure

• stiffness of lung
• pressure required to generate lung volume changes

Question 2

why do we breath where we breathe (in terms of our breath)?

Answer 2

• we don’t breathe at a fully inflated lung with a high recoil pressure and we don’t breathe at a fully deflated lung with very little leak recoil
  THEREFORE — there is a specific lung volume (level of inflation) where it is the most efficient and easiest for us to breathe
• this is where compliance comes in
• we breath at the steepest portion of a lung volume to pressure ratio. to achieve a change in volume, it is the least amount of pressure because it is steeper

Question 3

where is the most efficient place to breathe regarding our lung volume?

Answer 3

in the middle part of our breath because we don’t breathe at the ends of our lung volumes (full/empty)
- least amount of pressure required to move air

Question 4

when is it harder to breath air in?

Answer 4

at the beginning of our breath because …..

Question 5

why in the middle of our breath is it the easiest?

Answer 5

highly compliant portion of the lung

Question 6

why is it hard to keep breathing in?

Answer 6

because the transpulmonary pressure is getting too stretched

Question 7

why do we stay in the steepest point of normal compliance when breathing?

Answer 7

most energy efficient, little effort required
- least amount of pressure change, least amount of recoil pressure, least amount of muscular work

Question 8

what does a decreased compliance lung have to do in order to get to a given lung volume?

Answer 8

they have to have larger changes in pressure

Question 9

since the formula for compliance is delta v/ delta p, decreased compliance is due to?

Answer 9

high pressure low volume

Question 10

if compliance is so bad, what can it constrict?

Answer 10

inflating your lung all the way

Question 11

what is a disease characterized by a highly compliance lung?

Answer 11

emphysema
- lose elastic recoil of the lung because blood vessels are damaged and it is over stretched

Question 12

why is having highly compliant lungs a problem?

Answer 12

it would make breathing out harder

Question 13

why does highly compliant lungs make breathing out harder?

Answer 13

has decreased recoil pressure so you will need to recruit your expiratory muscles each breath

Question 14

why do we not need muscles to move air out resting?

Answer 14

recoil pressure

Question 15

increased compliace = __________ stiffness

Answer 15

decreased

Question 16

decreased compliance = ___________ stiffness

Answer 16

increased

Question 17

what is the equation for compliance?

Answer 17

= delta V / delta P

Question 18

what is an example of something characterized by decreased compliance?

Answer 18

lung fibrosis

Question 19

what is being lost in a highly compliant lung if it is easier to breath in?

Answer 19

the recoil pressure. it will make it harder to breath out

Question 20

what gets lost when the lungs get stretched out?

Answer 20

all the alveoli capillaries get destroyed and you lose the elastic nature. easy to breath in, but you lose the recoil

Question 21

what does lungs elastic recoil refer to?

Answer 21

how readily the lungs rebound after having been stretched

Question 22

what is lungs elastic recoil responsible for?

Answer 22

lungs returning to their preinspiratory volume when inspiratory muscles relax at end of inspiration

Question 23

what is the importance of recoil pressure on expiration?

Answer 23

allows us to exhale passively
- we would need to recruit expiratory muscles to exhale

Question 24

lungs elastic recoil depends on what?

Answer 24

• highly elastic connective tissue in the lungs
• alveolar surface tension (the ability to balance out the alveolar pressure from each alveoli throughout the lung) (without this we will have a stiff lung)

Question 25

What does the lung produce that helps us regulate surface tension?

Answer 25

Surfactant

Question 26

why does babies have a hard time breathing?

Answer 26

they don't produce surfactant - they cannot regulate the tensions and pressures in the alveoli

Question 27

type ii alveolar epithelial cells reduce?

Answer 27

surface tension in alveoli to make it easier to inflate

Question 28

what is the equation of Law of Laplace?

Answer 28

P = 2T/R pressure = 2 surface tension / radius

Question 29

what are the important benefits of surfactant?

Answer 29

helps us to maintain pressures across alveoli of different sizes. Also maintains surface tension to optimize compliance - reduces work of the lungs - reduces recoil pressure of smaller alveoli more than larger alveoli

Question 30

what does the lung produce that helps us regulate surface tension?

Answer 30

surfactant

Question 31

what are the two types of alveolar epithelial cells?

Answer 31

type i: flat for gas exchange type ii: secretes surfactant

Question 32

what happens if you do not have surfactant within alveolus?

Answer 32

it can cause issues

Question 33

what is surfactant?

Answer 33

a complex mixture of lipids and proteins secreted by type 2 alveolar cells

Question 34

where does surfactant disperse?

Answer 34

between the water molecules in the fluid lining the alveoli and lowers alveolar surface tension

Question 35

what are the two key factors to maintain a healthy compliance?

Answer 35

1. the elastic nature of the lung 2. the ability to maintain alveolar pressure through the use of surfactant

Question 36

the use of surfactant helps to maintain _____ across alveoli that may or may not have different volumes.

Answer 36

pressure - all based on the law of laplace - surfactant helps regulate surface tension

Question 37

if there is not surfactant between two alveoli of different radius', the surface tension will be the same in both but the pressure will be higher in the smaller alveolus. what will happen?

Answer 37

the air goes from high to low pressure. and the smaller alveolus will collapse due to no air being in it

Question 38

if there is surfactant between two alveoli of different radius', what happens?

Answer 38

the concentration will be higher in the smaller alveolus, so it is going to uniquely change the surface tension accordingly to allow for the pressure to be maintained in both of them. so now air flow between alveolus

Question 39

true or false: surfactant helps regulate surface tension to avoid pressure differentials across alveoli (individual alveolus units)

Answer 39

true this is a key study note - with surfactant, P(a) = P(b) due to the differential effects of surfactant on surface tension in each alveolus. Therefore air will not flow from a to b and air will be equally distributed throughout the lung

Question 40

what is Purcells law?

Answer 40

flow = delta pressure / resistance

Question 41

what generate the velocity or flow of air?

Answer 41

the amount of resistance that it is overcoming

Question 42

if you have two tubes, one with lower resistance and the other with high resistance, which will have increased flow?

Answer 42

lower resistance

Question 43

does low or high airway resistance make it easy to breathe?

Answer 43

low airway resistance

Question 44

is airway resistance normally very high or very low?

Answer 44

very low

Question 45

what is airway resistance dependent on?

Answer 45

a) tube length (generally fixed) b) interactions between gas molecules (variable) c) airway radius (regulated) --> by far most important

Question 46

decreased radius is often going to need ____ pressure to overcome the increased resistance?

Answer 46

increased

Question 47

pressure generation in the lung and the airways is highly dependent on the?

Answer 47

resistance - so if you have high resistance you are going to have to create larger pressures to overcome that

Question 48

flow = ?

Answer 48

delta pressure / resistance

Question 49

resistance = ?

Answer 49

delta pressure / flow

Question 50

same pressure, but resistance is higher in one than the other. which has a higher flow?

Answer 50

the one with the lower resistance

Question 51

is airway resistance different as we branch out?

Answer 51

yes - the flows are a little bit slower - the resistance is different at the terminal bronchioles than it is at the trachea

Question 52

what are the physical factors that will affect airway resistance?

Answer 52

1. transpulmonary pressure (as recoil pressure goes up, the volume in the lung is increasing) (however airway resistance decreases on a breath by breath basis as we inspire) 3. mucous accumulation in the lung (decreases diameter so it will increase the resistance)

Question 53

why is airway resistance decreasing when we breath in?

Answer 53

because there is a very small subtle increase in airway diameter when we breathe in