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Respiratory Physiology > Ventilation and Compliance > Flashcards

Ventilation and Compliance Flashcards

1
Q

What is the anatomical dead space defined as?

A

Volume of gas occupied in conducting airways that isn’t exchanged

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2
Q

What is the anatomical dead space volume?

A

Around 150ml

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3
Q

What volume of air is usually inhaled and exhaled per breath at rest (tidal volume)?

A

Around 500ml each way

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4
Q

What is the expiratory reserve volume (ERV) defined as?

A

How much air you can force out after a normal exhalation

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5
Q

What is the average expiratory reserve volume?

A

1100ml

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6
Q

What is the inspiratory reserve volume defined as?

A

The maximum you can breathe in NOT lung capacity

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7
Q

What is the volume of the IRV

A

3000ml

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8
Q

What is the inspiratory capacity?

A

The inspiratory reserve + a normal inhaled breath

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9
Q

What is the value of the inspiratory capacity?

A

3500ml

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10
Q

What is the vital capacity?

A

The max volume of air you can shift in one breath

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11
Q

What two other volumes is the vital capacity defined by and what does it equal?

A

Inspiratory capacity + expiratory reserve volume = 4600ml

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12
Q

What is functional residual capacity?

A

Volume of air left in the lungs after a normal exhalation

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13
Q

What other two volumes is the functional residual capacity defined by and what does it equal?

A

Expiratory reserve volume + residual volume = 2300ml

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14
Q

What is the residual volume?

A

The volume of air that can’t be expelled from the lungs = 1200ml

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15
Q

What is the point of the residual volume (2 points)?

A
  • Keeps the alveoli partially inflated so that it is easier to breathe in on the next breath - Maintains a pressure gradient for gas exchange to continue between breaths
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16
Q

What is pulmonary ventilation and is it functionally significant?

A

The total air movement in and out of the lungs, no

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17
Q

What is alveolar ventilation?

A

The volume of fresh air reaching the alveoli and therefore available for gas exchange

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18
Q

What will alveolar ventilation indicate?

A

The amount of gas exchange occurring

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19
Q

If lung volume = 2200ml after a normal exhilation, how high will the volume be after a normal inhilation?

A

2700ml

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20
Q

How much of the 500ml breath will reach the alveoli?

A

350ml as 150ml will be in the dead space

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21
Q

Describe what is going on in the diagram

A
  • Respiratory cycle
  • Indicating that the not all of the 500ml inhaled air will reach the alveoli for gas exchange
  • 150ml MUST always be in the anatomical dead space
  • After expiration, the anatomical dead space is filled with stale air
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22
Q

When should you consider the implication of stale air in the anatomical dead spaces when dealing with patients?

A
  • Anxious patients will have a low tidal volume and a high RR which means their pulmonary ventilation will be normal but the alveolar ventilation will be low (hypoventilation)
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23
Q

What is hyperventilation?

A

When more air reaches the alveoli and alveolar ventilation is higher than normal, but pulmonary is the same

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24
Q

What is the partial pressure?

A

Pressure of a gas in a mixture of gases = % of gas in the mixture x the pressure of the whole gaseous mixture

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25
EXAMPLE OF PARTIAL PRESSURE CALCULATION
Atmospheric Pressure = 760mmHg Pressure of air we breathe therefore = 760mmHg 21% of air we breath = O2 Partial pressure of O2 in air we breath = 21% x 760mmHg = 160mmHg
26
What do the pressures of O2 and CO2 do under normal conditions in the alveoli?
Remain constant
27
What is the normal PO2 in kPa and mmHg?
- 13.3kpA - 100mmHg
28
How can PO2 and PCO2 vary?
With hyper and hypo ventilation
29
What happens to PO2 and PCO2 during hypoventilation?
- PCO2 increases to 100mmHg - PO2 decreases to 30mmHg
30
What happens to PO2 and PCO2 ​during hyperventilation?
- PO2 increases to about 120mmHg - PCO2 decreases to about 20mmHg
31
What cells produce surfactant?
Type 2 pneumocytes
32
What is the main function of surfactant?
- Reduces surface tension
33
What is surface tension?
The attraction between air and water due to the attraction between water-water molecules, as shown below
34
What does surface tension encourage the alveoli to do?
Collapse
35
What is the definition of compliance?
Change in volume related to change in pressure, i.e. how much the lungs will inflate with an increase of intrapleural pressure
36
What is the effect of surfactant on compliance and lung recoil?
- Increased compliance - Reduced lung recoil
37
What effect does surfactant ultimately have on breathing
Makes it easier
38
During embryonic development, at what stage does surfactant production begin?
25 weeks
39
What can an inability to produce surfactant result in in newborns?
Infant Respiratory Distress Syndrome
40
What is the law of laplace?
P = 2T/r P - pressure T - surface tension r - radius
41
If the alveolus was bigger, why would the pressure be lower?
Increase the value of r in P = 2T/r which would mean a lower pressure
42
What is found in the lungs to counteract the small R?
Surfactant reduces the value of T so P is still low
43
Why is surfactant more effective in small alveoli?
Found in higher concentrations due to less space
44
What is high compliance?
Lung volume increases with a small intrapleural pressure increase
45
When does a high compliance occur?
- Healthy lungs - Emphysema
46
Why is there a high compliance with emphysema?
- Elastase is activated - Reduces elastin in the lungs - Lungs can't expand as far as they should so less air is taken in when intrapleural pressure is reduced
47
What is low compliance?
- Low volume increase from a large pressure change in the lungs
48
Where would you see low compliance?
- Unhealthy lungs - Bronchitis - Restrictive disease
49
What does compliance tell you about and what does it not give an indication of?
- Tells you about how effectively the lungs fill up - Does not give any indication into elastic recoil
50
Why does intrapleural have to become more negative during inspiration than expiration?
- Has to overcome surface tension - Expiration has the aid of elastic recoil
51
Why does inspiration follow an exponential curve?
- Similar to spontaneous reactions in that in needs some more energy to start - Imagine blowing up a balloon and that it gets easier after you have it going
52
Why is higher pressure needed to expire as you breathe out?
Need to overcome a higher resistance as airway muscle contracts to push air out
53
Why is normal expiration passive?
Elastic recoil
54
Why do people with emphysema have to expend more energy to breathe out?
Loss of elastic tissue means loss of elastic recoil
55
Why does fibrosis reduce compliance?
More work needed to inflate the alveoli as they don't stretch
56
Which part of the lung has better compliance and which part has worse compliance?
- Bottom of the lung is better - Apex is worse
57
Why does the bottom of the lung have better compliance?
Due to gravity more air is forced out of the alveoli at the bottom of the lung, the apex retains a higher reserve volume so doesn't intake as much air
58
What is an obstructive respiratory disease attributed with?
Air flow obstruction particularly during expiration
59
State 3 obstructive diseases
- Asthma - Bronchitis - Emphysema
60
How many people worldwide are affected by COPD?
80 million
61
What type of disease is fibrosis?
Idiopathic
62
Exposure to what can cause restrictive pulmonary disease?
Asbestos
63
Give 2 examples of restrictive diseases
- Fibrosis - Asbestosis - IRDS - Oedema - Pneumothorax
64
What 5 things can spirometry measure?
- Tidal volume - Expiratory Reserve - Inspiratory Reserve - Inspiratory Capacity - Vital Capacity
65
What is static spirometry?
Measures volume of air exhaled
66
What is dynamic spirometry?
Time taken to exhale a certain volume
67
What does FEV1/FVC stand for?
Forced expiratory volume in 1 second/forced vital capacity
68
What is FEV1/FVC usually equal to?
80%
69
What FEV1/FVC would an obstructive disease show?
A smaller percentage
70
What FEV1/FVC would an restrictive disease show?
- Both air flow rate and lung capacity is reduced - Percentage remains high

Respiratory Physiology (16 decks)

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