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BMS12 > Respiration 1 > Flashcards

Respiration 1 Flashcards

1
Q

What are the main functions of the respiratory system? (4)

A

Provide oxygen and remove carbon dioxide

Phonation

Protection from microbes and other foreign matter

Regulate blood pH

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2
Q

Why is the transport of gases in the blood referred to as bulk flow?

A

Blood carrying the gases is pumped around the body (gases do not move through blood)

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3
Q

What is the main difference between bronchi and bronchioles?

A

Cartilage is present in bronchi only

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4
Q

Why does bronchiole smooth muscle contract?

A

Prevent irritants and particles entering the alveoli

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5
Q

How many alveoli does one human lung have?

A

400 million

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6
Q

What is the surface area of your lungs?

A

85m squared

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7
Q

How thin can the walls of the alveoli be?

A

As little as 0.2um

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8
Q

What is diffusion of a gas across a membrane proportional to?

A

(Surface area/thickness) x gas permeability

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9
Q

What is tidal volume?

A

Volume of air breathed in per breath during normal steady/quiet breathing

500ml

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10
Q

What is inspiratory reserve volume?

A

Maximum amount that lung volume can be increased by above tidal volume

3000ml

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11
Q

What is expiratory reserve volume?

A

Maximum amount of air that can be exhaled after tidal volume has been expired

1200ml

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12
Q

What is residual volume?

A

Volume of air remaining in lungs after maximum exhalation

1200ml

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13
Q

What are capacities?

A

Sum of two or more volumes

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14
Q

What is inspiratory capacity the sum of and what is its average value?

A

Tidal volume + inspiratory reserve volume

3500ml

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15
Q

What is (forced) vital capacity the sum of and what is its average value?

A

Tidal volume + inspiratory reserve volume + expiratory reserve volume

4700ml

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16
Q

What is functional residual capacity the sum of and what is its average value?

A

Residual volume + expiratory reserve volume

2400ml

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17
Q

What is total lung capacity the sum of and what is its average value?

A

Residual volume + expiratory reserve volume + inspiratory reserve volume + tidal volume

5900ml

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18
Q

Why can a spirometer not be used to directly measure residual volume?

A

Lungs cannot be completely emptied so no ‘baseline’ can be recorded

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19
Q

What is ventilation?

A

Exchange of air between atmosphere and alveoli

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20
Q

What is V̇E and how do you calculate it?

A

Minute ventilation

Total ventilation per minute = breathing rate x tidal volume

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21
Q

What is V̇A?

A

Alveolar ventilation

Volume of fresh air reaching alveoli per minute

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22
Q

How do you calculate V̇A?

A

Minute ventilation - dead space ventilation (~4200ml/min)

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23
Q

What is the anatomical dead space and its average value?

A

Volume of purely conducting airways ~150ml

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24
Q

What are the standard units of pressure?

A

kPa

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25
Q

What is the equivalent of 1kPa in mmHg?

A

7.5mmHg

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26
Q

What is Darcy’s law regarding ventilation?

A

Flow = (Palv - Patm)/R

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27
Q

In between breaths, what is Palv relative to Patm and how can we tell?

A

0

No air flow so no gradient present

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28
Q

What is Boyle’s law regarding pressure?

A

Pressure of gas at a constant temperature is inversely proportional to the volume of its container

29
Q

How is the negative pressure between the pleura generated when at functional residual capacity?

A

Respiratory muscles are relaxed

Inward recoil of lungs is balanced by outward recoil of chest wall

30
Q

What is intrapleural pressure?

A

Pressure between pleural membranes

Usually negative

31
Q

What does transpulmonary pressure do and how is it calculated?

A

Palv - Pip

Transmits changes in pressure from chest expansion to alveoli

32
Q

Describe the steps involved in inspiration.

A
  1. Nerves stimulate diaphragm and other inspiratory muscles to contract to expand chest wall
  2. Pip falls to -0.7kPa
  3. Ptp increases so alveoli expands
  4. Palv falls by Boyle’s law
  5. Air moves into lungs down pressure gradient
33
Q

Describe the steps involved in expiration.

A
  1. Nerves decrease firing to diaphragm and intercostals (relaxation)
  2. Expanded chest wall recoils inward
  3. Pip and Ptp return to pre-inspiratory level
  4. Expanded lungs reduce in size
  5. Air is compressed, increasing Palv and forcing air out of lungs
34
Q

Which muscles (other than diaphragm) are most helpful in forced expiration?

A

Abdominals

35
Q

Where is airway resistance most significant?

A

Conducting airways

Especially middle order bronchi

36
Q

Why don’t bronchioles increase resistance more than bronchi even though they have smaller diameters?

A

Much more numerous and arranged in parallel

37
Q

What type of air flow occurs in quiet breathing?

A

Laminar

38
Q

Why is your breathing noisy during heavy exercise?

A

Turbulent air flow

39
Q

How does congestion affect air flow?

A

Increases resistance so decreases air flow

40
Q

What type of disease is increased airway resistance a feature of?

A

Obstructive lung disease

41
Q

Give three examples of obstructive lung diseases.

A

Asthma

Chronic bronchitis

Emphysema

42
Q

What is asthma?

A

Obstructive lung disease

Smooth muscle is hypersensitive to constrictors

Smooth muscle thickening and inflammation

43
Q

What is chronic bronchitis?

A

Obstructive lung disease

Inflammation

Hypertrophied glands in airways produce excess mucus

44
Q

What is Poiseuille’s law (basic)?

A

Resistance is inversely proportional to radius to the power of 4

45
Q

How is flow and radius connected (simple)?

A

Flow is proportional to radius to the power of 4

46
Q

What are examples of dilators of airway smooth muscle?

A

Carbon dioxide

Adrenaline - β2-adrenoceptors

47
Q

What are examples of constrictors of airway smooth muscle?

A

Vagus nerve - ACh and M3 receptors

Inflammatory mediators

48
Q

How does Ptp affect bronchioles during inspiration?

A

Expands bronchioles via lateral traction exerted by connective tissue

49
Q

How is lung compliance calculated?

A

Change in lung volume/change in Ptp

50
Q

What is lung compliance?

A

Measure of how easily lungs are expanded by a given change in pressure

Determines the amount of work that must be done by respiratory muscles

51
Q

How is Ptp measured?

A

Subject inhales in steps from residual volume to total lung capacity

At each step, measure volume inspired and Pip

No airflow so Palv = Patm so Ptp = -Pip

52
Q

On a lung volume/Ptp graph, how can you calculate the lung compliance?

A

Find the slope/gradient of the curve

53
Q

What determines lung compliance?

A

Resistance of tissues to stretch influenced by extracellular matrix composition

Resistance due to surface tension in alveoli

54
Q

How does lung fibrosis affect compliance?

A

High resistance of tissues to stretch

Decreased compliance

55
Q

How does emphysema affect compliance?

A

Low resistance of tissues to stretch

Increased compliance

56
Q

What does abnormally low compliance suggest?

A

Fibrosis - restrictive lung diseases

57
Q

What does abnormally high compliance suggest?

A

Emphysema - obstructive lung diseases

58
Q

What is emphysema?

A

Tissue destruction causes alveolar spaces to fuse which decreases surface area

Bronchioles collapse more easily on expiration which traps air

59
Q

What is surface tension?

A

Force at an air-fluid interface caused by water molecules attracting each other and forming intermolecular bonds

60
Q

What is the equation linking pressure, radius and surface tension (Laplace)?

A

P = 2T/r

61
Q

If there was no surfactant, what would happen to relatively smaller alveoli?

A

Much greater internal pressure due to Laplace’s law

Air moves down pressure gradient into larger alveoli and smaller alveoli collapse - impairs gas exchange

62
Q

Why do we need surfactant in alveoli?

A

Reduces surface tension to protect lungs/alveoli from collapsing

63
Q

How does surfactant work to protect from collapse?

A

Greater concentration of surfactant in smaller alveoli so surface tension is lower

Hence internal pressure of smaller alveoli becomes almost equal to larger alveoli

No flow/collapse

64
Q

What are two simple pulmonary tests used to measure lung function?

A

Vitalographs

Peak flow meters

65
Q

What is a vitalograph?

A

Plots changes in lung volume over time during a single forced expiration

66
Q

How can a vitalograph be used to give evidence for different lung diseases?

A

Obstructive diseases - unable to force out 75% volume in one second but lung volume is normal (decreased FER<50%)

Restrictive diseases - force out more than 75% volume in one second but unable to expand lung to full (increased FER>90%)

67
Q

How do you calculate forced expiratory ratio?

A

Forced expiratory volume in one second / forced vital capacity

68
Q

What does a peak flow meter measure?

A

Peak expiratory flow rate

69
Q

How can you work out the peak expiratory flow rate from a vitalograph?

A

Find the gradient at the start of the breath (steepest gradient)

BMS12 (7 decks)

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