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FBS2 > Intro to respiratory system (physiology) > Flashcards

Intro to respiratory system (physiology) Flashcards

1
Q

What is the difference between external and internal respiration?

A

External respiration - between air and blood

Internal respiration - between blood and cells

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2
Q

What is pulmonary ventilation?

A

The movement of air into and out of lungs

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3
Q

What does ventilation rely on?

A

A pressure gradient along the airways

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4
Q

What is the equation for flow pressure and resistance? (like Ohm’s Law)

A

Flow = pressure gradient/resistance

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5
Q

What is a low flow rate caused by?

A

Low pressure gradient/high resistance

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6
Q

What must be the relationship between the atmospheric pressure and the alveolar pressure for inspiration to occur?

A

Atmospheric pressure (at mouth/nose) must be greater than alveolar pressure

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7
Q

What is Boyles law?

A

The pressure of a fixed number of molecules is related to the volume of the container.
ie pressure and volume are inversely related - decreasing the volume increases the pressure and vv.

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8
Q

What mechanically couples the lungs to the chest wall?

A

The pleural fluid

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9
Q

What prevents the lungs from collapsing inwards?

A

The outward recoil of the chest wall

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10
Q

What pressure is the intrapleural space held at resting end expiration?

A

Negative pressure (-5cm H20)

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11
Q

Which thoracic structure wants to recoil outwards and which inwards?

A

Lungs want to spring inwards
Chest wall wants to spring outwards
2 opposite elastic forces
These forces are exactly equal just before inspiration

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12
Q

What happens during inspiration?

A

Contract respiratory muscles to increase volume of thoracic cavity
Decreases the intrapleural pressure - becomes more negative
Lung expands even further (pressure lower inside than outside) –> air moves in

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13
Q

At rest, is expiration active or passive?

A

Passive

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14
Q

Are pressures given absolute in respiratory physiology?

A

No - relative to atmospheric pressure

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15
Q

Is inspiration active or passive?

A

Always active - inspiratory muscles contract (diaphragm esp important)

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16
Q

Name the obligate inspiratory muscles

A

Diaphragm
External intercostal muscles
Scalenes
Parasternal intercostal muscles

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17
Q

Name the accessory inspiratory muscles

A

Sternocleidomastoids

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18
Q

Name the expiratory muscles

A 
Internal intercostals
Rectus abdominis
External oblique
Internal oblique
Transversus abdominis
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19
Q

What is Ppl?

A

Intrapleural pressure

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20
Q

What is PA?

A

Alveolar pressure

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21
Q

What is Pb?

A

Barometric pressure

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22
Q

How do you calculate transmural pressures?

A

Pressure differential of the inside compartment minus the outside

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23
Q

What is PL and how do you calculate it?

A

Transpulmonary pressure/distending pressure that inflates the lung
PL = PA - Ppl

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24
Q

What is PL at rest?

A

+5 (0–5)

Positive pressure holding the lung open (‘distending pressure’)

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25
Q

What happens to PL during inspiration?

A

It increases

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26
Q

When may the intrapleural pressure become positive?

A

During forced expiration

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27
Q

What is a pneumothorax?

A

After a chest wall puncture - air is sucked into the pleural space
Collapse of the lung due to elastic recoil inwards
Chest wall springs outwards

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28
Q

What is a respiratory cycle?

A

A single cycle of inhalation and expiration

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29
Q

What is the term for the volume of air moved in 1 respiratory cycle?

A

Tidal volume

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30
Q

What is a normal value for a tidal volume?

A

500ml

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31
Q

What is FRC?

A

Functional residual capacity

Volume of air that you start breathing in from

32
Q

What is the vital capacity?

A

The difference between the maximum amount of inspired air and the volume after a maximum expiration

33
Q

What is TLC?

A

Total lung capacity (total volume of long)

34
Q

What is the expiratory reserve volume?

A

Difference between the vital capacity and the inspiratory capacity
(volume left over after a normal breath out)

35
Q

What is the inspiratory reserve volume?

A

Volume that you have left to breath into after a normal breath in to take you up to the vital capacity

36
Q

What is the inspiratory capacity?

A

Difference between functional residual capacity and total lung capacity

37
Q

What is the residual volume?

A

The volume of air left in the lungs after forced expiration that cannot be breathed out

38
Q

Which lung volumes cannot be measured directly by spirometry?

A

Total lung capacity
Residual volume
Functional residual capacity

39
Q

What is dead space? (Vd)

A

Airway volume with no gas exchange

40
Q

What is anatomic dead space?

A

All of airway except alveoli and respiratory bronchioles, e.g. trachea

41
Q

What is physiologic dead space?

A

Anatomic plus areas where gas exchange is dysfunctional

42
Q

Which kind of dead space increases in respiratory disease e.g. emphysema?

A

Alveolar dead space (therefore physiologic dead space)

43
Q

What is the equation for physiologic dead space?

A

Physiologic dead space = anatomical dead space + alveolar dead space

44
Q

What is the relationship between alveolar and anatomical dead space in a healthy individual?

A

They should be approximately equal

45
Q

What is a typical total ventilation rate?

A

7500ml/min

46
Q

What is a typical anatomical dead space?

A

150ml

47
Q

What is a typical alveolar gas volume?

A

3000ml

48
Q

What is a typical pulmonary capillary blood volume?

A

70ml

49
Q

What is a typical ventilation frequency (resps)?

A

15/min

50
Q

What is a typical pulmonary blood flow rate?

A

5000ml/min

51
Q

What is the equation for alveolar ventilation?

A

Minute ventilation - dead space ventilation

52
Q

What is a typical value for alveolar ventilation?

A

5250ml/min

53
Q

What is important about the values for alveolar ventilation and pulmonary blood flow rate?

A

It is well matched (both around 5000 ml/min)

54
Q

What are the two main sources of resistance to breathing?

A
  1. Elastic resistance of the lung (due to elastic tissues and air-liquid interface in alveoli)
  2. Airway resistance to airflow (due to friction from air flowing within tube)
55
Q

What is dyspnoea?

A

Breathlessness

56
Q

What is lung compliance?

A

Stretchiness of the lung

57
Q

What is the equation for lung compliance?

A

Change in long volume/change in transmural pressure gradient (V/P)

58
Q

What is the equation for airway resistance?

A

Airway resistance = alveolar pressure-mouth pressure/flow at mouth

59
Q

What are the two types of flow?

A

Laminar or turbulent

60
Q

What is turbulent flow?

A

Disruption of laminar flow due to hitting a branch point etc - more oscillations of airflow (wheeze)
Increases resistance

61
Q

What causes a wheeze?

A

Oscillations of airflow (turbulent flow) down a narrow airway

62
Q

What could a silent wheeze from an asthmatic suggest?

A

Very severe obstruction - insufficient airflow to generate wheeze

63
Q

What determines airway resistance?

A

Poiseuille’s law (R is proportional to 1/r^4)

Radius has largest effect on resistance

64
Q

What are the main sites of airway resistance?

A

Wherever the tubes get narrower
Nose, pharynx, larynx
Medium bronchi

65
Q

Which part of the airway contributes most to airway resistance?

A

Medium bronchi at generation 3-5

66
Q

What are the two main factors causing variations in airway resistance (RAW)?

A

Factors within the airways, e.g. bronchial SM tone

Pressure across airway wall (if collapsing the airway down)

67
Q

What effect does CO2 have on bronchial muscle tone?

A

Relaxes

68
Q

What effect do NANC nerves have on bronchial muscle tone?

A

Relax

69
Q

What effect does B2 receptor stimulation have on bronchial muscle tone?

A

Relaxes

70
Q

What does salbutamol do?

A

B2 agonist

Relaxes bronchial SM in ashtmatics

71
Q

What effect does histamine and prostaglandins have on the bronchial SM?

A

Contract SM

72
Q

What affect does activation of airway irritant receptors have?

A

Contraction via brainstem pathway

inhibited by pulmonary stretch receptors

73
Q

What occurs during dynamic compression of the airways?

A

Positive pressure in alveoli during forced expiration
(due to expiratory muscles contracting plus inward recoil of lungs) +38 within alveoli
At some point this alveolar pressure decreases below the intrapleural pressure so there is a positive pressure pushing the lung in –> airway collapse

74
Q

Where is dynamic compression of the airways most likely to occur?

A

Bronchi at generation 3/4

those without collagen/cartilage

75
Q

What does dynamic compression of the airways limit?

A

Forced expiration - it is effort independent at low lung volume (can’t decrease the volume anymore)

76
Q

What causes dynamic compression of the airways?

A

High intrapleural pressures

77
Q

What is the problem with dynamic compression of airways in lungs with RAW?

A

It causes marked limitation in airflow and slow expiration

- low peak flow, wheeze and air trapping

FBS2 (16 decks)

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