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I've got hypertension > Lecture 14 > Flashcards

Lecture 14 Flashcards

1
Q

Explain the process of inspiration

A

this is an active process, it requires the active involvement of diaphragm and external intercostal muscles

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2
Q

Explain the process of expiration

A

this is a passive process at rest, due to the elastic recoiling which pulls the thorax inwards and relaxed diaphragm inwards

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3
Q

What does subatmospheric mean?

A

less than atmospheric

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4
Q

What is the equation for transpulmonary pressure?

A

P(alv) - P(ip)

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5
Q

What happens when the diaphragm and inspiratory intercostals contract?

A

The thorax expands and so the P(ip) becomes more subatmospheric (less than atmospheric pressure). This increases P(tp) because P(tp) = P(alv) - P(ip).

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6
Q

As the transpulmonary pressure increases, the ________ increases which means that the ________ increase in size. What does this mean for the pressure?

A

volume
alveoli
this means the pressure inside the alveoli (Palv) goes down to be less than atmospheric pressure

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7
Q

When the pressure inside the lungs is less than the pressure outside the lungs, what happens?

A

air flows from the atmosphere into the lungs

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8
Q

Describe the events during expiration

A

The diaphragm stops contracting and intercostals (if exercising) contract so the diaphragm domes back to its original position.
This means that the chest wall recoils inward. P(ip) moves back toward preinspiration value. The transpulmonary pressure moves back toward the preinspiration value. The lungs recoil towards preinspiration size. The lung is collapsing so the air in the alveoli becomes compressed. P(alv) becomes greater than P(atm) and due to the pressure gradient, the air flow out of the lungs

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9
Q

At the end of expiration, there is no air flow between the __________ and the ________

A

atmosphere

lungs

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10
Q

When we start inspiring, the ________ pressure becomes more __________ which means __________ pressure has become more positive. This allows the lungs to _________ so the _________ pressure goes down. This is creating a pressure gradient and because alveolar pressure is less than _________ pressure, air flows _______ the lungs

A 
intrapleural
negative 
transpulmonary
expand
alveolar
atmospheric 
into
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11
Q

Why is the intrapleural pressure made more negative during inspiration?

A

There are inspiratory muscles trying to expand the chest outwards and the lung is trying to collapse

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12
Q

At the end of inspiration, the pressure between the __________ and the _________ is stabilised so _______ air is flowing in or out.

A

alveoli
atmosphere
no

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13
Q

During expiration, the diaphragm goes back so there is no more inspiratory muscle force so it is only the lung elastic force trying to collapse the lung so the __________ pressure starts to increase which creates a gradient between alveoli and __________ so air is flowing ________

A

alveolar
atmosphere
outwards

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14
Q

If Patm=0 mmHg and Palv = 4 mmHg, then
1. Transpulmonary pressure is -4 mmHg
2. It is the end of the normal expiration and there is no
airflow
3. Transpulmonary pressure is +4 mmHg
4. Air is flowing out of the lung
5. It is the end of the normal inspiration and there is no air flow

A
  1. Air is flowing out of the lung
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15
Q

What are the two determinants of lung volume?

A
  • Difference in the pressure between the inside and outside of the lung (transpulmonary pressure (Ptp or PL ))
  • Stretchability of the lungs (compliance) – how much the lungs expand for a given change in Ptp
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16
Q

What is the work of breathing?

A

this is the work that your respiratory system needs to do to maintain breathing

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17
Q

The work of breathing is the air done to do what two things?

A
  1. overcome the elastic properties (stiffness) of the lung (how hard it is to expand the lungs)
  2. overcome the airway resistance (how hard it is to move air in and out)
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18
Q

What two things affect the stiffness of the lungs?

A
  • compliance

- surfactant

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19
Q

Define compliance

A

magnitude of the change in the lung volume (ΔVL) produced by the given change in the transpulmonary
pressure (ΔPtp)

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20
Q

What is the equation for compliance?

A

CL=ΔVL ⁄ΔPtp

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21
Q

What are the two compliance curves?

A
  • inspiratory

- expiratory

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22
Q

What are the two axes of the compliance curve?

A

x: intrapleural pressure
y: lung volume

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23
Q

A more negative intrapleural pressure means what for the transpulmonary pressure?

A

it is more positive

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24
Q

Why is the compliance curve not linear?

A

Because inspiration requires more energy due to the contraction of the diaphragm and maybe intercostals. Since you are expending energy, you need more energy to expand the lungs. This means that it is more like x^2
Expiration is passive so it requires less energy than inspiration so the curve is like sqroot(x)

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25
Q

Low ________ = “stiff lungs” means Need to do more _______ to expand. Give an example of a condition where this occurs

A

compliance
work
fibrosis

26
Q

As well as the stiffness, what is another factor that determines how hard it is to expand the lungs?

A

the surface tension

27
Q

Describe the surface tension in the alveolar?

A

Inside the alveoli, the alveolar wall is lined by water molecules. These water molecules always try to bond together. This tries to collapse the alveoli ie. it prevents the alveoli from expanding so therefore we need to overcome this force to expand the lungs.

28
Q

What do we use to overcome the surface tension in the alveoli?

A

surfactant

29
Q

What is the purpose of surfactant?

A

it reduces the surface tension in alveoli and makes it easier for them to expand

30
Q

Where is surfactant released from?

A

alveolar type 2 cells

31
Q

What is the major constituent in surfactant?

A

phospholipids

32
Q

How does surfactant reduce surface tension?

A
  • it reduces the attractive forces between fluid molecules lining the alveoli
  • this means the surface tension in the alveoli is reduces and it is easier to increase lung size
33
Q

How does surfactant affect compliance?

A

Surfactant lowers surface tension and reduces the attractive forces between fluid molecules lining the alveoli. This means that the surface tension in the alveoli is reduced and it is therefore easier to increase lung size ie. there is increased compliance

34
Q

Lack of surfactant/failure to produce surfactant results in what?

A

stiff lungs

35
Q

What is respiratory distress syndrome and who gets it?

A

This is when surfactant is absent in premature infants

36
Q

How do we treat respiratory distress syndrome?

A

assisted ventilation and administration of natural or synthetic surfactant given through the infant trachea

37
Q

Which alveolar are most likely to collapse and are therefore most likely to need surfactant?

A

smaller ones

38
Q

Surfactant:
A. lowers surface tension at the fluid-gas interface of the alveoli
B. stabilizes the smaller alveoli, thereby preventing them from collapsing due to high pressure.
C. is a mixture of both lipids and protein, but its major component is protein.
D. All of A, B and C are correct.
E. Only A and B are correct.

A

E. Only A and B are correct.

39
Q

What is the purpose of sighing?

A

When we are sitting, we sigh to activate the type 2 alveolar cells to release surfactant so the lung breathing patter goes back to normal

40
Q

As well as doing work to overcome the elastic properties of the lung, we need to do work to overcome the _________ __________

A

airway resistance

41
Q

Air flow is mainly in a __________ flow during quiet breathing

A

laminar

42
Q

Resistance to air flow is determined by Poiseuille’s Law. What does this state?

A

R = 8nl/πr^4

43
Q

R is inversely proportional to what?

A

r^4

44
Q

What is a condition that affects the viscosity?

A

cystic fibrosis (because the mucus become thicker)

45
Q

_____________ and __________ is important elements in airways resistance

A

bronchoconstriction

bronchodilation

46
Q

What is a condition where the resistance is increased?

Explain this

A

asthma

this is when there is bronchoconstriction which decreases the radius of the bronchi and this increases the resistance

47
Q

How can we treat people with asthma?

A

with broncodilators

48
Q

Where is the main area of airway resistance?

A

in the bronchi

49
Q

Most of the resistance to airflow arises in the first 6 _________ of the airway

A

generations

50
Q

Resistance is strongly dependent on the radius. Why is it then that the bronchi are the main area of airway resistance even though they have a larger radius than the bronchioles?

A

Because as we go down our respiratory system, the airflow becomes lesser and lesser (less flow, less resistance)
and also because the airway down to our respiratory bronchioles to the alveoli are arranged in parallel which reduces the resistance

51
Q

What are two factors affecting airway resistance in normal conditions?

A
  • lung volume

- radial traction

52
Q

Explain lung volume as a factor affecting the airway resistance in normal conditions

A

The volume increases during expiration (due to an increase in transpulmonary pressure), the airway radius becomes larger and so the resistance becomes lower and so the lung expands.

53
Q

Explain radial traction as a factor affecting the airway resistance in normal conditions

A

Each alveoli are attached to each other so when an alveoli expands, this results in the pulling of other alveoli. This means that the expansion of one alveoli results in the expansion of other alveoli. This increases the radius and decreases the resistance

54
Q

What are diseases where the airway resistance is affected?

A
  • asthma
  • chronic obstructive pulmonary disease (COPD)
    eg. emphysema, chronic bronchitis
55
Q

What is chronic obstructive pulmonary disease (COPD)?

A

This is when all the alveoli starts to lose their wall and become a single alveolar structure so there is not enough surface for the gas exchange to take place but it also increases the resistance because they a large space and therefore can’t expand

56
Q

Describe the pressure volume loop which can be use to describe the wok of breathing

A

the work to overcome the elastic resistance is the work required to expand the lung
the work to overcome the non-elastic resistance of the lung is the work required to move air in and out due to airway resistance

57
Q

Fibrosis reduces the _________ of the lung. How does this affect the pressure volume loop?

A

compliance

More work to overcome elastic resistance (0ABCD, yellow) because you have to do more work to stretch the lung
The pressure/volume curve shifts to the right
(Similar work to overcome non-elastic resistance)

58
Q

Describe emphysema

A

The alveoli walls fuse together to form one alveoli so it loses its elasticity. It is too flaccid.

59
Q

Describe the effect of obstructive lung disease on the pressure/volume curve

A

Similar work to overcome elastic resistance (0ABCD) ie. similar work to expand the lung
• More work to overcome non-elastic resistance, inspiration (AECB) ie. spend more energy pushing the lung back to its original position
• More work to overcome non-elastic resistance, expiration (ABCF) A more positive expiratory pressure is required (DF0 area), expiration becomes active process
• A more negative intra pleural pressure (Pip) required to move the same amount of air (inspiratory flow rates, 0AECD area)

60
Q

Which of the following statements are correct regarding airway resistance?
(i). Airflow velocity decreases as the size of the airways become smaller, hence the highest resistance is seen in the respiratory bronchioles.
(ii) Air way resistance is inversely related to the fourth power of the radius (r4).
(iii). In healthy individuals, inspiration reduces the airway resistance due to an increase in the transpulmonary pressure (Ptp).
(iv). Asthma increases airway resistance.
A. (i), (iii) and (iv) are correct. B. (ii), (iii), (iv) are correct.
C. (i), (ii) and (iv) are correct. D. only (ii) and (iii) are correct.
E. all of the above are correct.

A

B. (ii), (iii), (iv) are correct.

I've got hypertension (47 decks)

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