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Physiology 3001 > Ventilation: Physics of breathing > Flashcards

Ventilation: Physics of breathing Flashcards

1
Q

How does air move?

A

From high to low pressure

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2
Q

How is the pressure inside the lungs lowered?

A

By expanding the chest and lungs

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3
Q

What is the intrapulmonary pressure?

A

The pressure within the alveoli

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4
Q

What is the intrapleural pressure?

A
  • The elastic nature of the lung tissue versus ribcage and thorax trying to pull apart visceral from parietal pleura.
  • Always more negative than intrapulmonary
  • -4 mmHg (756)
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5
Q

What is more negative the intapleural or intrapulmonary pressure?

A

The intrapleural pressure

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6
Q

What is normal atmospheric pressure?

A

760 mmHg (0 mmHg)

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7
Q

What is the collapsing force of lung?

A

4 mmHg

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8
Q

What is the role of the diaphragm?

A
  • Main muscle of respiration
  • Contraction flattens domes
  • Allows lungs to increase in size
  • Abdominal wall relaxes to allow abdominal contents to move downwards
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9
Q

What is the role of the intercostals (externals) in respiration?

A
  • With first rib fixed, two movements, forward movement of lower end of the sternum, and upward and outward movement of ribs
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10
Q

What is the value of normal tidal volume?

A

~500ml

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11
Q

What is the intrapleural pressure in quiet inspiration?

A

~ -6 mmHg (drops by another 2 mmHg)

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12
Q

How much does the intrapulmonary pressure decrease by during inspiration?

A

~ 1 mmHg

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13
Q

What is quiet expiration?

A
  • PAssive movement of lungs
  • Elastic recoil drives air out of lungs
  • Thoracic volume decreases by 500ml
  • Intrapulmonary pressure increases
  • air moves down pressure gradient
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14
Q

What is forced expiration?

A
  • Expiration where abdominal walls are contracted, forces abdominal contents up against diaphragm, and internal intercostals - pull ribs downwards
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15
Q

How long on average is the respiratory cycle?

A

4 seconds

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16
Q

What is the trans-pulmonary pressure?

A

The difference between the intrapulmonary and intrapleural pressure

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17
Q

What is the resting intrapleurl pressure?

A

756 mmHg

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18
Q

What percentage of energy expenditure in quiet breathing is due to contraction of the diaphragm?

A

75%

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19
Q

What is energy used for in breathing?

A
  • Contract the muscles of inspiration (e.g diaphragm)
  • Stretch elastic elements
  • Overcome airway resistance
  • Overcome frictional forces arising from the viscosity of the lung and chest wall
  • Overcome inertia of the air and tissues
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20
Q

What is airway resistance?

A
  • The most significant non-elastic source of resistance
  • F = DiffP/R
    Amount of air that flows is determined by the change of pressure divided by the resistance
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21
Q

When is turbulent flow of air more likely?

A
  • High velocities

- Large diameter airways

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22
Q

What percentage of airway resistance is due to the upper airways?

A

1/3

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23
Q

Where is the greatest resistance to airflow and why?

A
  • Segmental bronchi

- Cross sectional area is relatively low and airflow is high and turbulent

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24
Q

What is flow like in the smallest airways?

A

Laminar

25
Q

What is the resistance like in the smallest airways?

A

Small

26
Q

What is an over-inflated ‘barrel-chest’ usually a result of?

A

COPD

27
Q

What is the effect of inspiration on airway resistance?

A

Decreases

28
Q

What is the definition of compliance?

A

The ease of stretch of the lung tissue when external force applied, or the ease with which the lungs expand under pressure

29
Q

What pressure change causes a change in volume of the chest?

A

Change in intrapleural pressure

30
Q

How does a high compliance influence volume?

A

High compliance means there is a large change in volume for a given change in pressure

31
Q

What are the major determinants of compliance?

A
  • Elastic components

- Alveolar surface tension

32
Q

What is compliance in a normal healthy individual?

A

~ 1 L per kPa (1 L per 7.5 mmHg)

33
Q

What can compliance be reduced by?

A
  • Replacing elastic tissue with non-elastic tissue - pulmonary fibrosis - lungs become stiffer
  • Blocking smaller respiratory passages
  • Increasing alveolar surface tension
  • Decreasing the flexibility of the thoracic cage or its ability to expand
34
Q

What can compliance can be increased by?

A

Pulmonary emphysema. Due to alveolar rupture, creating larger air space and thus reducing surface area of lung. Impaired elastic recoil leads to poor deflation, trapping more air

35
Q

Why is compliance greater at the base of the lung compared with the apex?

A

The base of the lung is more compressed than the apex. For the same change in intrapleural pressure at inspiration the base of the lung expands more than the apex

36
Q

What does surfactant do?

A
  • Lines alveoli

- Increases lung compliance by reducing surface tension - allows greater expansion for a given change in pressure

37
Q

What is surfactant produced by?

A

Type II alveolar cells

38
Q

What is surfactant made up of?

A

phospholipids

39
Q

What is a capacity?

A

Volumes added together in various combinations

40
Q

What is the definition of tidal volume (TV)?

A

Volume of air breathed in and out in a single breath (500ml)

41
Q

What is the definition of inspiratory reserve volume (IRV)?

A

Volume breathed in by max inspiration at end of normal inspiration

42
Q

What is the value of inspiratory reserve volume (IRV)?

A

3.3L

43
Q

What is the defintion of expiratory reserve volume (ERV)?

A

Volume of air expelled by max effort at the end of normal expiration

44
Q

What is the value of expiratory reserve volume (ERV)?

A

1 L

45
Q

What is the definition of residual volume (RV)?

A

The volume of air in the lungs at the end of maximum expiration

46
Q

What is the value of residual volume (RV)?

A

1.2 L

47
Q

What is the inspiratory capacity (IC)?

A
  • TV + RV
  • Volume of air breathed in by max inspiration at the end of a normal expiration
  • 3.8 L
48
Q

What is the functional residual capacity (FRC)?

A
  • ERV + RV
    Vol air left in lungs at the end of normal expiration. Buffer against extreme change in alveolar gas levels in each breath
  • 2.2 - 2.4 L
49
Q

What is the vital capacity (VC)?

A
  • IRV + TV + ERV
  • Vol of air that can be breathes by max inspiration following max expiration
  • 4.8 L
50
Q

What is the total lung capacity (TLC)?

A
  • VC + RV
  • Only a fraction of TLC used in normal breathing
  • 6.1 L
51
Q

What is a spirometer?

A

Used to measure and record volumes of inspired and expired air. The graph produced is called a spirogram

52
Q

What does a vitalograph measure?

A

Expired air in 1 second FEV1

53
Q

What would the affect of asthma be on FEV1?

A

Decreased FEV1

54
Q

What would the affect of pulmonary emphysema be on FEV1?

A

Increased FEV1

55
Q

What is the dead space?

A

The volume of ventilated air not involved in gas exchange

56
Q

What happens to the alveolar dead space in certain lung conditions?

A

Increases

57
Q

What is the anatomical dead space?

A
  • Areas of airway not involved in gas exchange

- 150 ml

58
Q

What is the alveolar dead space?

A
  • The volume of air in alveoli that is not perfused

- 5 ml

59
Q

What is the physiological dead space?

A
  • Anatomical plus alveolar

- Almost the same as anatomical in a healthy individual

Physiology 3001 (20 decks)

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