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MD3001 - Respiratory Physiology > Physics of Breathing > Flashcards

Physics of Breathing Flashcards

1
Q

What is pulmonary ventilation?

A

movement of air into and out of the lungs

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2
Q

What causes airflow into and out of the lungs?

A
  • Δ volume
  • Δ pressure
  • Airflow follows a change in pressure resulting from the change of volume of the lungs
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3
Q

How does air flow?

A

From an area of high pressure to an area of low pressure

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4
Q

How is low pressure created inside the lungs?

A

Increasing the volume by expanding the chest and lungs

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5
Q

What is intrapulmonary pressure?

A

pressure within the alveoli

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6
Q

How does intrapulmonary pressure change within a respiratory cycle?

A

falls and rises over one respiratory cycle

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7
Q

What is intrapleural pressure?

A

pressure within the pleural cavity, which is always more negative than alveolar pressure

-4mmHg

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8
Q

What is responsible for trying the pull the visceral pleura away from the parietal pleura?

A

elastic nature of the lung tissue versus the ribcage and thorax (more rigid structures)

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9
Q

What is usually contained within the pleural cavity?

A

fluid

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10
Q

Draw a diagram of the lungs indicating the intrapleural and intrapulmonary pressure and the collapsing force of the lungs

A
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11
Q

What leads to change in pressure in inspiration?

A

change in volume

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12
Q

What is the main muscle of respiration?

A

Diaphragm

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13
Q

What is the role of the diaphragm in inspiration?

A
  • contraction flattens domes
  • abdominal wall relaxes to allow abdominal contents to move downwards
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14
Q

What muscles are used in forced inspiration (respiratory distress)?

A

accessory muscles

e.g. trapezius

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15
Q

What is the role of the intercostal muscles in inspiration

A

external intercostal muscles

with first rib fixed, the have 2 movements:

  • forward movement of lower end of sternum
  • upwards and outwards movement of the ribs
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16
Q

What is the normal tidal volume of an average person?

A

500ml

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17
Q

What happens to the intrapleural pressure in inspiration?

A

drops to -6mmHg

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18
Q

What happens to the intrapulmonary pressure in inspiration?

A

decreases by ~1mmHg

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19
Q

What occurs in quiet expiration?

A
  • passive - no direct muscle action
  • cessation of muscle contraction
  • elastic recoil
  • thoracic volume decreases by 500ml
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20
Q

What happens to the intrapulmonary pressure during quiet expiration?

A

increases (by 1mmHg)

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21
Q

What happens to air in quiet expiration?

A

moves down the pressure gradient and out of the lungs

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22
Q

What occurs in forced expiration?

A

Contraction of abdominal walls, forces abdominal contents up against diaphragm and internal intercostals

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23
Q

What pressure indicates the differnce beywen intrapleural and intrapulmonary pressure?

A

transpulmonary pressure

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24
Q

Draw a diagram showing the pressure changes that occur during inspiration and expiration with values

A
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25
Q

During breathing what is energy required to do?

A
  • contract muscles of inspiration
  • stretch elastic elements
  • overcome airway resistance
  • overcone fricitional forces arising from viscosity of the lungs and chest wall
  • overcome inertia of the air and tissues
26
Q

What is the most significant source of non-elastic resistance?

A

airway resistance

27
Q

F = ΔP/R

A

the amount of air that flows is determined by the change in pressure divided by resistance

28
Q

How much does the upper respiratory tract contribute to airway resistance?

A

1/3

29
Q

Where os the greatest resistance to airflow found? And why?

A

segmental bronchi

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

30
Q

What type of flow is found in the smallest airways?

A

laminar

31
Q

What happens to airway resistance in inspiration?

A

decreases

32
Q

What occurs to airway resistance in asthma?

A

inflammatory mediators change smooth muscle tone narrowing the airway and increasing resistance

33
Q

What is compliance?

A

describes the distensibility or ease of stretch of lung tissue when external force is applied, or the ease with which the lungs expand under pressure (ease of stretching with external force)

34
Q

What is the meaning of high compliance?

A

there is a large change in volume for a given change in pressure

35
Q

What occurs due to compliance?

A

Change in volume of the chest that results from a given change in intrapleural pressure

36
Q

What are tje major determinants of compliance?

A

elastic components

alveolar surface tension

37
Q

What can compliance be reduced by?

A
  • replacing elastic tissue with non-elastic tissue –> pulmonaru fibrosis (lungs become stiffer)
  • blocking smaller respiratory passages
  • increasing alveolar surface tension
  • decreasing the flexibility of the thoracic cage or its ability to expand e.g. rib fracture
38
Q

What can compliance be increased by?

A
  • pulmonary emphsema (easier to breath in but harder to expel air due to impaired elastic recoil)
  • alveolar rupture creating large air spaces and reducing the SA of the lung
  • impaired elastic recoil leads to poor deflation, trapping more air
39
Q

What does compliance vary with?

A

lung volume

40
Q

When is compliance greatest?

A

at lower lung volumes

41
Q

When is compliance lowest?

A

higher lung volumes

42
Q

What does compliance help explain? And what part of the lung is most compliant

A

the difference in ventilation between the apex and base of the lung

Apex is more complaint

43
Q

What helps reduce the alveolar surface tension?

A

Surfactant

44
Q

What is surfacant made of and what produces it?

A

phospholipid

type II alveolar cells

45
Q

What does surfactant prevent?

A

alveolar collapse

46
Q

What is the main purpose of surfactant?

A

Increases lung compliance by reducing alveolar surface tension. Allows for greater expansion for a given change in pressure

47
Q

Draw a diagram indicating all the major lung volumes and capacities

A
48
Q

What is tidal volume?

A

Volume of air breathed in and out in a single breath

500ml

49
Q

What is inspiratory reservce volume?

A

volume breathed in by maz inspiration at the end of normal inspiration (max in after normal breath)

3.3L

50
Q

What is expiratory reserve volume?

A

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

1L

51
Q

What is residual volume?

A

volume of air in the lungs at the end of maximal expiration (you cannot expel all of the air in the lung)

1.2L

52
Q

What is inspiratory capcity?

A

Tidal Volume + Inspiratory Reserve Volume

volume of air breathed in by maximal inspiration at the end of a normal expiration

3.8L

53
Q

What is functional residual capcity?

A

Expiratory reserve volume + residual volume

Volume of air left in the lungs after normal expiration. Buffer against extreme changes in alveolar gas levels in each breath

2.2-2.4L

54
Q

What is Vital Capcity?

A

Inspiratory Reserve Volume + Tidal Volume + Expiratory Resvere Volume

Volume of air that can be breath by maximal inspiration following maximal expiration

4.8L

55
Q

What is Total lung capacity?

A

Vital Capcity + Residual Volume

Total capcity of the lungs

6L

56
Q

What is spirometry?

A

Measures how much air you inhale and exhale and how fast you can exhale.

Indicates lung capacity

57
Q

What is FEV1.0 ?

A

Forced expiratory volume

The amount of air you can force out of your lungs in 1 second

58
Q

What is anatomical dead space?

A

areas of airways not involved in gaseous exchange

e.g. nose and mouth, pharynx, larynx, bronchioles etc

59
Q

What is alveolar dead space?

A

gas exchange suboptimal in some parts of the lung (less ventilation)

60
Q

What is physiological dead space

A

anatomical plus alveolar

61
Q

What can increase alveolar dead space?

A

altering the ventilation:perfusion ratio

MD3001 - Respiratory Physiology (8 decks)

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