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Heart, Lungs and Blood > mechanics of breathing pressures and work > Flashcards

mechanics of breathing pressures and work Flashcards

1
Q

what is the shape of the diaphragm

A

large dome-shaped muscle

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2
Q

what is the function of the diaphragm

A

active muscle in breathing

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3
Q

what are the 3 major apertures of the diaphragm

A
  • IVC at T8
  • esophagus at T10
  • aorta at T12
  • I ate 10 eggs at noon
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4
Q

what are the posterior attachments of the diaphragm

A

attaches posteriorly to L1 and L2 via left and right cura or tendinous extensions

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5
Q

what is the arcuate ligament

A

left and right cura come together to form arch

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6
Q

what are the anterior attachments of the diaphragm

A

bottom of the sternum

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7
Q

what are the lateral attachments of the diaphragm

A
  • ribs 6-12 and costal cartilages
    • forms costal part of diaphragm
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8
Q

what is the innervation of the diaphragm

A
  • cervial segments (C3,4,5)
    • creates phrenic nerve
      C345 keeps the diaphragm alive
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9
Q

what does the phrenic nerve do

A

contains motor and sensory nerve fibers to support the diaphragm

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10
Q

what do the lower thoracic nerves do

A

lower thoracic nerves innervate the periphery

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11
Q

what happens to the diaphragm during expiration

A

relaxed and reaches 5th thoracic segment

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12
Q

what happens to the diaphragm during inspiration

A

contracts downwards

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13
Q

what happens to the lungs during inspiration

A
  • lung has elastic recoil that is inwardly directed
  • inspiration causes a negative pressure within the alveoli which allows air to rush into the lungs
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14
Q

what do the intercostals as a whole do during inspiration

A

they stiffen the chest wall and prevent intercostal spaces from being sucked inwards

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15
Q

what does the external intercostals do during inspiration

A

assists the expansion during inspiration by increasing the antero-posterior and lateral diameter of the thorax

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16
Q

what do the internal intercostals do during expiration

A

decreasing thoracic volume

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17
Q

what do scalene muscles from the cervical vertebrae to the first rib and the sternocleidomastoid do

A

help elevate the rib cage

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18
Q

what does the anterior abdominal wall do during inspiration

A

muscles relax to allow for full descent of the diaphragm during inspiration and contract during forced inspiration

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19
Q

how does bronchial circulation return to the heart

A

azygos or pulmonary vein

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20
Q

what is respiration

A

respiration describes the exchange for CO2 for O2 deep in the lungs and tissues

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21
Q

what is ventilation

A

ventilation describes the process by which we move air into and out of the lungs for gas exchange

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22
Q

what do accessory muscles do

A

accessory muscles of respiration are recruited to generate extra force, required to move the large volumes of air during deep breathing

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23
Q

what are the accessory muscles of expiration

A

Rectus and transversus abdominis and the internal and external obliques- expiration

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24
Q

what is intrapleural pressure

A

intrapleural pressure is the pressure within the pleural space

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25
Q

what is the pleural space

A

Pleural space is the visceral pleura lining long in the parietal pleura lining the chest wall

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26
Q

what is the intrapleural pressure under normal conditions

A

negative

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27
Q

what is the alveolar pressure

A

pressure within the alveoli

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28
Q

what is the alveolar pressure during inspiration

A

negative

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29
Q

what is the alveolar pressure during expiration

A

positive

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30
Q

what is the alveolar pressure when there is no air movement

A

equal/0

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31
Q

what is the alveolar pressure when there is no air movement

A

equal/0

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32
Q

what is transpulmonary pressure

A

It is the difference between the pressure inside and outside of a system

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33
Q

how do you calculate transpulmonary pressure

A

It is calculated by subtracting the intrapleural pressure from that Alveolar pressure

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34
Q

why must transpulmonary pressure be positive

A

for the alveoli and the lung to expand

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35
Q

what is Boyle law

A
  • As volume of the close system increases the pressure decreases
  • As volume of the close system decreases, the pressure increases
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36
Q

what happens to the alveolar pressure when the diaphragm contracts

A

the alveolar volume expands and the Alveolar pressure decrease.
Once the pressure has become negative air flows into the alveoli

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37
Q

what happens to alveolar pressure when expiration occurs

A

Expiration occurs when the diaphragm relaxes in the alveoli volume decreases, so the pressure increase

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38
Q

what is minute ventilation (VE)

A

calculates the total volume of gas entering the lungs per minute

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39
Q

how do you calculate VE

A

VE= Vt(tidal volume) x RR (resp rate)

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40
Q

what is dead space

A

Dead space ventilation is a volume of gas that does not participate in respiration

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41
Q

where does dead space ventilation occur

A
  • It occurs in the conducting (bronchial tree) and respiratory (alveoli) zones
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42
Q

what is anatomical dead space

A

anatomical dead space consists of the areas of the lungs that are structurally, incapable of gas exchange e.g. trachea, bronchi, and the terminal bronchioles

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43
Q

what is alveolar dead space

A

Alveolar dead space consists of the alveoli that cannot participate in gas exchange, due to insufficient perfusion

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44
Q

what is alveolar ventilation

A

alveolar ventilation (Va) is the rate of air that reaches the alveoli and participates in ventilation

45
Q

how do you calculate alveolar ventilation (Va)

A
  • Va-(Vt-Vd) x RR
  • Vd is physiologic dead space
46
Q

what is Vd/Vt

A

Vd/Vt is the ratio of dead space to tidal volume

47
Q

how do you calculate Vd/Vt

A

Vd/Vt = (PaCO2 - PeCO2) / PaCO2

48
Q

what is PaCO2

A

is the partial pressure of carbon dioxide in the arterial blood

49
Q

what is PeCO2

A

PeCO2 is the partial pressure of carbon dioxide in the expired (exhaled) air.

50
Q

what is cellular respiration

A

Metabolism of nutrients in cells (Kreb’s cycle) consuming O2 and releasing CO2

51
Q

what is Tidal Volume (VT)

A

volume of each breath

52
Q

what is the mechanics of inspiration

A
  • Intercostal muscles elevate and evert the ribs
  • Diaphragm moves downward
  • Scalene muscles (inserted into the first 2 ribs) raise the upper ribs and push the sternum forward
  • Sloping lower ribs rise and move out
53
Q

what is bucket handle action

A

Sloping lower ribs rise and move out = the bucket handle action and the transverse diameter of the chest wall ↑

54
Q

what is pump action

A

Scalene muscles (inserted into the first 2 ribs) raising the upper ribs and push the sternum forward (pump action) and ↑the A-P diameter of the thoracic cavity

55
Q

what happens at the end of inspiration

A

recoil of lungs and chest wall

56
Q

what kind of ventilation usually occurs for adults at rest

A

diaphragmatic

57
Q

what is the overall action of muscles during inspiration

A
  • Diaphragm contracts
  • Intercostal muscles contract
    • Bucket-handle
  • Scalene muscles contract
  • Sternum rises
  • This causes AP expansion of the thoracic cavity
58
Q

is expiration an active or passive process

A

passive

59
Q

why does expiration occur

A

Occurs due to elastic recoil of the lungs and the chest wall

60
Q

what is the pressure like during expiration

A

During expiration, both intrapleural pressure and alveolar pressures rise

61
Q

what is required during forced expiration

A

Forced expiration(eg coughing/sneezing) requires contraction of the abdominal walls which push the diaphragm upward

62
Q

what type of pressure determines wether air will enter or leave the lungs

A

intra-alveolar

63
Q

why does intrapleural pressure not equilibrate with the atmosphere

A

pleural space is closed and fluid filled.

64
Q

how does the chest wall affect pressure

A

Chest wall exerts a distending pressure on the pleural space which is transmitted to the alveoli to increase their volume, lower the pressure, and generate airflow inwards

65
Q

what does distending mean

A

swell or cause to swell by pressure from inside.

66
Q

what is the transpulmonary pressure equal and opposite to

A

elastic recoil pressure of the lungs
So it sucks the lungs out and sucks the lungs back in, ensuring the lungs don’t collapse

67
Q

what is functional residual capacity (FRC)

A

FRC = the volume of air left in the lungs at the end of a normal breath

68
Q

what are the respiratory muscles like at FRC

A

relaxed and the lungs and chest wall recoil in opposite directions

69
Q

what is the recoil like at FRC

A

the outward recoil of the chest wall exactly balances the inward recoil of the lungs

70
Q

what is the volume of air determined by at FRC

A

the elastic properties of the lungs and the chest wall

71
Q

what affects FRC

A
  • Pulmonary fibrosis: lungs are stiff and small, ↑ elastic recoil, then FRC is ↓
  • Emphysema: loss of alveolar tissue and ↓ elastic recoil, then FRC is ↑
72
Q

what is impedance

A

Impedance = Frictional Airway Resistance and Elastic Resistance to stretching of the lungs and chest wall

73
Q

what are the elastic forces on the lungs

A

To breathe in, the inspiratory muscles contract to overcome the impedance offered by the lungs and chest wall

74
Q

what is lung compliance

A

the ability of the lungs to stretch and recoil during ventilation (CL = change in lung volume/unit change in distending pressure)

75
Q

what is the distending pressure

A

is the pressure difference across the lung = alveolar-intrapleural pressure

76
Q

what is the mechanics of compliance

A
  • On exhalation, there is elastic recoil of lungs
    This is balanced by the tendency of chest wall to recoil in opposite direction
  • At end of quiet expiration, the pressures balance
77
Q

what is static pressure

A
  • The curve flattens as the lung volume approaches TLC. The inspiratory curve is slightly different from the expiratory curve = hysteresis
  • Hysteresis is a common property of elastic bodies
  • Static lung compliance is the slope of the steepest part of this curve (just above FRC)
78
Q

how is the dynamic pressure-volume loop obtained

A

from continuous measurements of intrapleural pressure and volume during a normal breathing cycle.

79
Q

how do you find the dynamic pressure-volume loop

A
  • At the end of inspiration and expiration, airflow and alveolar pressures are zero
  • The slope of the line joining these points is dynamic compliance
80
Q

when is dynamic pressure different to static compliance

A

in lung disease- stiff lungs

81
Q

when is the lung less compliant

A

in higher volumes

82
Q

what is the area of the dynamic loop

A

is a measure of the work done against airway resistance

83
Q

what does lung compliance depend of

A

how inflated or not it is

84
Q

what is hysteresis

A

The compliance curves are different for inspiration and exhalation.
due to frictional resistance changes

85
Q

when is compliance decreased

A

in a lung with interstitial fibrosis Compliance is decreased due to more stiff alveolar walls from scarring (called fibrosis)

86
Q

when is compliance increased

A

in emphysema Compliance is increased due to loss of alveolar interdependence

87
Q

when does laminar flow occur

A

During quiet breathing there is Laminar air flow in airways

88
Q

what is laminar flow

A
  • Gas particles move parallel to the walls of bronchi
  • Centre layers move faster than outer ones creating a cone-shaped front
89
Q

where does turbulent flow occur

A

Turbulent flow occurs at higher linear velocities in wide airways and near branch points

90
Q

when does turbulent flow occur

A

Turbulent flow occurs in trachea during exercise = harsh breath sounds

91
Q

what is airway resistance (RAW)

A

RAW is the pressure difference between the alveoli and mouth divided by the flow rate

92
Q

what does RAW affect

A

RAW affects ventilation and has to be overcome (together with the elastic recoil) and inflate the lung

93
Q

where does RAW originate

A

RAW originates from friction between air and mucosa

94
Q

what does RAW depend on

A

radius of the conducting airways
tone of bronchial smooth muscle and epithelium
resting bronchomotor tone

95
Q

how does the radius of conducting airways affect RAW

A
  • Nose, pharynx and trachea = offer most resistance
  • Mouth breathing eg during exercise decreases resistance
  • Peripheral, smaller airways are affected by diseases → ↑ RAW
96
Q

how does tone of bronchial smooth muscle and epithelium affect RAW

A

Parasympathetic nerve supply affects bronchomotor tone
β-adrenergic receptors → relaxation
Nitric Oxide causes bronchodilatation

97
Q

how does Resting Bronchomotor tone affect RAW

A
  • Bronchoconstriction: ↓ radius→ ↑ resistance → ↓ airflow
  • Bronchodilatation: ↑ radius → ↓ resistance → ↑ airflow
98
Q

how does acute asthma affect RAW

A
  • Increased RAW
    • Bronchoconstriction
    • Mucosal oedema
    • Mucus hypersecretion
    • Mucus plugging
99
Q

how does COPD affect RAW

A
  • Bronchoconstriction
  • Chronic mucosal hypertrophy
100
Q

what are surface tension forces caused by

A

are caused by air-fluid interface in alveoli

101
Q

when does surface tension change

A

with age and lung disease

102
Q

how does surface tension occur

A

Cohesive forces between molecules at the surface of a bubble (alveolus) creates a tension which tends to shrink the bubble

103
Q

what does surface tension do

A

Alveoli and small airways are inherently unstable → collapse during expiration → atelectasis

104
Q

what is a pulmonary surfactant

A

mixture of phospholipids

105
Q

what is pulmonary surfactant produced by

A

Type II pneumocytes

106
Q

how does pulmonary surfactant aid ventilation

A

Hydrophilic and hydrophobic ends repel each other and interfere with liquid molecule attraction→ lowers surface tension

107
Q

why is surfactant important

A
  • Increases lung compliance because surface forces are reduced
  • Promotes alveolar stability
  • Prevents alveolar collapse
  • Surface tension tends to suck fluid from capillaries into alveoli
  • Important in defense against infection
108
Q

how does surfactant prevent alveolar collapse

A
  • small alveoli are prevented from getting smaller
  • large alveoli are prevented from getting bigger

Heart, Lungs and Blood (51 decks)

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