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Pulmonary ventilation mechanics Flashcards

1
Q

What is pulmonary ventilation?

A

The flow of air into and out of the lung alveoli from the atmosphere

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2
Q

What is inspiration?

A

Breathing in

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3
Q

What is tidal inspiration?

A

Breathing in at rest

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4
Q

What muscular activities occur during tidal inspiration?

A

Diaphragm contracts

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5
Q

What happens to the diaphragm when it contracts?

A

It moves downwards and flattens

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6
Q

What happens to the lungs themselves when the diaphragm contracts?

A

Diaphragm pulls lower surfaces of lungs downwards

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7
Q

What happens to the volume and pressure of the lungs when their lower surfaces are pulled downwards?

A

Volume of lungs increases

Pressure of lungs decreases below atmospheric pressure

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8
Q

How does the pressure decrease in the lungs affect the flow of air between the lungs and the atmosphere during inspiration?

A

Air moves from higher atmospheric pressure into the lungs, which are at a lower pressure
down the pressure gradient

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9
Q

What additional muscular activities occur during forced inspiration?

A

External intercostal muscles contract

Sternocleidomastoid, scalene and pectoralis muscles contract

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10
Q

How do the sternocleidomastoid, pectoralis and scalene muscles act to move the ribs?

A

Their other attachment is stabilised

so when they contract, they act on their attachment to the ribs and move the ribs

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11
Q

What happens to the ribs when the external intercostal, scalene and pectoralis muscles contract?

A

They move upwards and outwards

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12
Q

What happens to the sternum and ribs when the sternocleidomastoid muscle contracts? How?

A

Sternum moves anteriorly and superiorly by pull of sternocleidomastoid

Ribs moves upwards and outwards by pull of sternum

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13
Q

What happens to the lungs themselves when the external intercostal, sternocleidomastoid, scalene and pectoralis muscles contract?

A

Chest wall pulls anterior and lateral surfaces of lungs upwards and outwards

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14
Q

Why do the lungs move upwards and outwards as the chest wall does so?

A

Because the lungs are attached to the chest wall by the pleura

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15
Q

What is expiration?

A

Breathing out

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16
Q

What is tidal expiration?

A

Breathing out at rest

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17
Q

What muscular activities occur during tidal expiration?

A

Diaphragm relaxes

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18
Q

What happens to the diaphragm when it relaxes?

A

It moves upwards and resumes its normal dome-shape

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19
Q

What happens to the lungs themselves when the diaphragm relaxes?

A

Lower surfaces of lungs are no longer pulled downwards

elastic recoil of lungs moves them back up

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20
Q

What happens to the volume and pressure of the lungs when the lungs recoil?

A

Volume of lungs decreases

Pressure of lungs increases above atmospheric pressure

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21
Q

How does the increase in pressure in the lungs affect air flow between the lungs and atmosphere during expiration?

A

Air moves from the higher pressure in the lungs to the lower pressure in the atmosphere
down the pressure gradient

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22
Q

What additional muscular activities during forced expiration?

A

External intercostal muscles relax

Internal intercostal and abdominal muscles contract

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23
Q

What happens to the ribs when the external intercostal muscles relax and the internal intercostal muscles contract?

A

Ribs move downwards and inwards

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24
Q

What happens to the lungs themselves when the external intercostals muscles relax and the internal intercostal muscles contract?

A

Chest wall no longer pulls anterior and lateral surfaces of lungs upwards and outwards
elastic recoil of lungs moves them back down and in

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25
What happens to the lungs themselves when the abdominal muscles contract?
Abdominal muscles push contents of abdomen upwards push diaphragm upwards compress the lungs upwards
26
What are the pressures in the pleural space?
Inspiration = -7mmHg Expiration = -3mmHg
27
Why is the pressure in the pleural space negative?
Because the parietal pleura and visceral pleura are pulled in opposite directions
28
What direction is the parietal pleura pulled in? How?
Outwards by the chest wall wanting to spring outwards
29
What direction is the visceral pleura pulled in? How?
Inwards by the elastic recoil of the lungs
30
Why does the pressure in the pleural space become more negative with inspiration?
Chest wall moves upwards and outwards pulls on parietal pleura even more increases volume of space in pleural space, decreasing pressure
31
What is meant by compliance?
The ability of the lungs to distend
32
What is the equation for compliance?
Change in lung volume ____________________ Change in pleural pressure
33
What volume and pressure changes occurs in lungs with low compliance?
Low compliance means need bigger decreases in pleural pressure to pull the lungs and increase their volume
34
What volume and pressure changes occur in lungs with high compliance?
High compliance means need smaller decreases in pleural pressure to pull the lungs and increase their volume
35
What are the factors affecting compliance of the lungs?
Elastic recoil Fibrosis
36
How does elastic recoil of lungs affect lung compliance?
Need bigger decreases in pleural pressure to pull the lungs and increase their volume therefore decreases lung compliance
37
What causes the elastic recoil of the lungs?
Elastin fibers in the lung tissue Surface tension
38
What is the biggest cause of elastic recoil of the lungs?
Surface tension
39
How does elastin in the lungs change with age?
Decrease in amount of elastin
40
What is Laplace's law?
Pressure = 2 x surface tension / radius Pressure generated by the alveolar elastic recoil
41
What is surface tension?
When water is in contact with air the water molecules at the surface are strongly bonded to each other they attempt to move closer to each other to minimise the surface area
42
Where does surface tension occur in the lungs?
Alveoli
43
How does surface tension occur in the alveoli?
Water on inner surface of alveoli
44
What are the effects of surface tension in the alveoli?
Makes the alveoli collapse | smaller ones into larger ones
45
Why would smaller alveoli collapse into larger alveoli, as opposed to them evening out?
Smaller alveoli have smaller radius than larger ones therefore have higher pressure than larger ones air moves from higher pressure to lower pressure down the pressure gradient
46
What does surfactant stand for?
Surface active agent
47
What is surfactant made up of?
Complex mixture of lipids and proteins
48
Where is surfactant found in the lungs?
Alveoli
49
What is responsible for the surfactant found in the alveoli?
Type 2 pneumocytes
50
When does surfactant production in the alveoli begin?
25-28 weeks of gestational age
51
When is the amount of surfactant in the alveoli sufficient?
35 weeks of gestational age
52
What is the effect of surfactant on surface tension?
Decreases surface tension
53
How does surfactant decrease surface tension?
Surfactant spreads over inner surface of alvoeli | separates the water molecules at the surface from each other
54
How does surfactant affect the alveoli?
Prevents the smaller ones from collapsing into the larger ones
55
How does surfactant prevent smaller alveoli from collapsing into larger alveoli?
Surfactant molecules spread over inner surface of larger alveoli more thinly, less effective surface tension decreases less pressure decreases less equivalent to that of smaller alveoli
56
How does surfactant affect lung compliance?
Reduces elastic recoil of lungs need smaller decreases in pleural pressure to pull the lungs and increase their volume therefore increases lung compliance
57
What is the cause of respiratory distress syndrome of the newborn?
Babies born prematurely before 30 weeks | have less surfactant in their alveoli, increased surface tension, alveolar collapse
58
What are the signs of respiratory distress syndrome of the newborn?
Intercostal and subcostal recession
59
Why is intercostal and subcostal recession seen with respiratory distress syndrome of the newborn?
Reduced pressure in the lungs | draws overlying attached muscles and skin inwards
60
How is respiratory distress syndrome of the newborn treated?
Surfactant replacement Oxygen Assisted ventilation If yet unborn, give glucocorticoid treatment to mother because it increases surfactant production in the foetus

Respiratory system (32 decks)

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