Mechanics Of Respiration Flashcards

1
Q

Inspiratory muscles

A
  • Sternocliedomastoid
  • Scalenes
  • External intercostals
  • Diaphragm
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2
Q

Process of inspiration

A
  • Ribs elevated
  • Sternum flares
  • Diaphragm moves downwards
  • External intercostals contract
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3
Q

Accessory muscles of inspiration function

A

Involvement in forced inspiration

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4
Q

Accessory muscles of inspiration examples

A
  • Scalene
  • Major/minor pectoralis
  • Sternocleidomastoid
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5
Q

Scalene during inspiration

A

Contraction enlarges the upper ribcage

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6
Q

Major/minor pectoralis during inspiration

A

Draws rib cage superiorly

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7
Q

Sternocleidomastoid durig inspiration

A

Elevates sternum

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8
Q

Process of expiration

A
  • Ribs and sternum depressed
  • Diaphragm relaxes and moves upwards
  • Recoil of lung
  • External intercostals relax
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9
Q

Accessory muscles of expiration function

A

• Active only in deep expiration

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10
Q

Accessory muscles of expiration examples

A
  • Internal intercostals
  • External abdominal oblique
  • Internal abdominal oblique
  • Transverse abdominis
  • Rectus abdominis
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11
Q

Internal intercostal muscles during expiration

A

Contract to depress the rib downwards

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12
Q

Abdominal muscles during expiration

A

Contract to force abdominal content up against relaxed diaphragm

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13
Q

Pulmonary pressures types

A
  • Intra-alveolar (intrapulmonary) pressure
  • Intrapleural pressure
  • Transpulmonic (transpleural) pressure
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14
Q

Transpulmonic pressure

A

P(alv) - P(ip)

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15
Q

Intra-alveolar pressure value at rest

A

P(av) = P(atm) = 760 mm Hg

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16
Q

Intra-alveolar pressure during normal inspiration

A

Slightly negative wrt atmospheric pressure -> air flows into lung

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17
Q

Intra-alveolar pressure during forced inspiration

A

Becomes more negative

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18
Q

Intra-alveolar pressure during passive expiration

A

Greater than atmospheric pressure

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19
Q

Intra alveolar pressure during forced expiration

A

Value increases (more positive)

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20
Q

Intrapleural pressure at rest

A

Subatmospheric (756 mmHg)

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21
Q

Intrapleural pressure during normal inspiration

A

-7 mmHg

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22
Q

Intrapleural pressure during normal expiration

A

-4 mmHg

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23
Q

Intrapleural pressure during forced inspiration

A

More negative

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24
Q

Intrapleural pressure during forced expiration

A

Becomes less negative, may exceed atmospheric pressure

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25
Q

Transpulmonic (transpleural) pressure definition

A

Pressure gradient across wall of lung
P(av) - P (ip)
Pressure that keeps lung from collapsing

26
Q

Transpulmonic pressure at rest

A

760 - 756 = 4 mmHg

27
Q

Transpulmonic pressure magnitude

A
  • ALWAYS positive

* More positive during inspiration

28
Q

Zero transpulmonic pressure

A
  • Lung collapses (atelectasis)

* Occurs when air enters intrapleural space (pneumothorax)

29
Q

Sequence of events during inspiration

A
  1. Diaphragm and external intercostals contract
  2. Thorax expands
  3. P(ip) becomes more subatmospheric
  4. Increase in transpulmonic pressure
  5. Lungs inflate
  6. P(av) becomes subatmospheric
  7. Air flows into alveoli
30
Q

Sequence of events during expiration

A
  1. Diaphragm & ext intercostals relax
  2. Chest wall moves inwards
  3. P(ip) back towards preinspiration value
  4. Decrease in transpulmonic pressure
  5. Lungs recoil
  6. P(av) becomes greater than P(atm)
  7. Air flows out of alveoli
31
Q

Nature of inspiration

A

Active process

32
Q

Types of forces

A
  • Lung elasticity
  • Alveolar surface tension
  • Airway resistance
33
Q

Lung elasticity definition

A

Ability of the lung to stretch/recoil

34
Q

Lung elasticity measurement

A

Measured by lung conpliance

35
Q

Lung compliance definition

A

Change in lung volume per unit change in distending pressure

36
Q

Lung compliance formula

A

C = Change in V/Change in P

37
Q

Higher compliance implication

A

Easier for lung to expand

38
Q

Lower lung compliance implication

A

More energy needed to breathe

39
Q

Lung compliance factors

A
  • Elasticity of lung and thoracic cage

* Surface tension in alveoli

40
Q

Alveolar surface tension

A

Force that reduces alveoli to smallest size, pulling lungs inwards

41
Q

Inflation of alveolus relationship

A

Distending pressure, tension and radius in walls of alveolus

42
Q

Law of Laplace

A

P = 2T/r

43
Q

Surfactant

A

Lipoprotein mixture secreted by type II alveolar cells into the alveoli

44
Q

Functions of surfactant

A
  • Decrease surface tension
  • prevent collapse of alveoli
  • Make lungs more distensible
45
Q

Greatest airway resistance location

A

Medium-sized bronchi

46
Q

Inspiratory reserve volume definition

A

Maximum amount inspired in excess volume of tidal volume

47
Q

Inspiratory reserve volume value

A

3100ml

48
Q

Tidal volume definition

A

Amount of air inspired or expired with each breath

49
Q

Tidal volume value

A

500ml

50
Q

Expiratory reserve volume definition

A

Maximum amount expired in excess volume of tidal volume

51
Q

Expiratory reserve volume value

A

1200ml

52
Q

Residual volume

A

Amount of air remaining in lungs after a maximum respiratory effort

53
Q

Residual volume value

A

1200ml

54
Q

Lung capacities types

A
  • Vital capacity
  • Functional residual capacity
  • Total lung capacity
55
Q

Vital capacity definition

A

Total amount of exchangeable air

56
Q

Vital capacity formula

A

IRV + TV + ERV = 3.2 + 0.5 + 1.2 = 4.8L

57
Q

Functional residual capacity definition

A

Amount of air left in lungs after tidal expiration

58
Q

Functional residual capacity definition

A

ERV + RV = 1.2 + 1.2 = 2.4L

59
Q

Total lung capacity definition

A

Maximum volume to which the lungs can be expanded with the greatest possible effort

60
Q

Total lung capacity formula

A

IRV + TV + ERV + RV = 3.1 + 0.5 + 1.2 + 1.2