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Physiology > Mechanics of Breathing > Flashcards

Mechanics of Breathing Flashcards

1
Q

What is ventilation?

A

movement of air between lungs and atmosphere

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2
Q

Airflow in and out of the respiratory system needs a…

A

pressure difference between atmosphere and the lungs

  • air moves from high pressure to low pressure
  • air gets pulled in and pushed out
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3
Q

What is inspiration?

A
  • inward movement of air
  • from atmosphere to lungs
  • chest cavity expands to lower pressure within chest
  • expends E
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4
Q

Inspiration requires which skeletal muscle contractions?

A
  • diaphragm (major muscle here)
  • external intercostals
  • sternocleidomastoid
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5
Q

What happens to the diaphragm during inspiration?

A
  1. contraction signaled by phrenic nerves
  2. diaphragm flattens
  3. abdominal contents are forced downwards
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6
Q

What impairs the diaphragm?

A
  • obesity
  • pregnancy
  • tight clothing
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7
Q

Which skeletal muscles are classified as accessory?

A
  • external intercostals
  • sternocleidomastoid
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8
Q

When are accessory muscles utilized for respiration?

A

deep respiration

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9
Q

What is expiration?

A

outward movement of air (from lungs to atmosphere)

  • chest cavity decreases in size to increase pressure within chest
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10
Q

During normal expiration, there is an increase in ______ due to…

A

pressure gradient due to:

  • passive elastic recoil of lung
  • decrease in size of chest due to relaxation of muscles of inspiration
  • no E expended
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11
Q

Forced expiration occurs when…

A
  • exercising
  • hyperventilation
  • coughing
  • sneezing
  • vomiting
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12
Q

Which muscles are involved in forced expiration?

A
  • abdominal wall muscles (most important)
  • internal intercostals
  • expends E
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13
Q

Contraction of abdominal wall muscles leads to…

A

abdominal contents being forced upward towards diaphragm

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14
Q

What is ambient air?

A

air we breathe

  • 79% N
  • 21% O
  • <1 % CO2
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15
Q

Air at sea level is what atm?

A

760 mmHg

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16
Q

For comparison purposes, the atmospheric pressure is set at…

A

0

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17
Q

What is the pressure inside the alveolus during inspiration and expiration?

A
  • inspiration: negative (less than ambient pressure)
  • expiration: positive (greater than ambient pressure)
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18
Q

What is pleural pressure?

A

pressure associated with pleural fluid in between chest wall and lung

  • usually negative compared to atm pressure
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19
Q

What is transairway pressure?

A

pressure in airway - pressure of pleural fluid

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20
Q

What happens to pleural pressure when expiration is forced?

A

turns positive and triggers airway collapse

  • air gets trapped within lungs
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21
Q

What is alveolar pressure?

A

pressure inside alveolus

  • 0 at rest
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22
Q

What is transpulmonary pressure?

A

pressure in alveolus - pressure of pleural fluid

  • always positive to prevent collapse of lungs
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23
Q

What is a pneumothorax?

A

introduction of air into pleural space

  • changes pleural pressure to 0 or positive
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24
Q

What happens during a pneumothorax?

A
  • air enters via punctured chest wall or ruptured lung
  • elastic recoil of lung causes lung to collapse
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25
Q

What are the pressure changes in normal breathing cycle?

A
  • end of expiration: no airflow (Pa=Pb)
  • mid inspiration: expansion of lung and chest cavity by muscle contraction and air flows in (Pa
  • end of inspiration: no airflow (Pa=Pb)
  • mid expiration: air flows out (Pa>Pb)
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26
Q

What are the pleural pressures during the normal breathing cycle?

A
  • end of expiration: -5
  • mid-inspiration: -7
  • end of inspiration: -8
  • mid-expiration: -6
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27
Q

Lung volumes and capacities are determined by…

A

balance between lungs elastic recoil properties and properties of muscles of chest wall

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28
Q

What is a spirogram?

A

graphs volume of air that’s moved into and out of lungs over time

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29
Q

What are the different types of lung volumes?

A
  • tidal volume (VT)
  • inspiratory reserve volume (IRV)
  • expiratory reserve volume (ERV)
  • residual volume (RV)
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30
Q

Definition of tidal volume:

A

volume of air moved in and out during quiet breathing

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31
Q

Definition of inspiratory reserve volume:

A

additional volume of air that can be inhaled during maximum inspiration

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32
Q

Definition of expiratory reserve volume:

A

additional volume of air that can be exhaled after normal expiration

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33
Q

Definition of residual volume:

A

volume of air left in the lungs after maximum expiration

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34
Q

Capacity is the sum of…

A

2 or more volumes

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35
Q

What are the types of capacity?

A
  • inspiratory capacity (IC)
  • vital capacity (VC)
  • total lung capacity (TLC)
  • functional residual capacity (FRC)
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36
Q

Definition of inspiratory capacity:

A

maximum volume that can move into lungs after normal expiration

  • tidal volume + IRV
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37
Q

Definition of vital capacity:

A

volume of air moved out from maximum inspiration to maximum expiration

  • IRV + VT + ERV = IC + ERV
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38
Q

Definition of total lung capacity:

A

total volume that can be in the lungs

  • varies with height
  • VC + RV
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39
Q

Definition of functional residual capacity:

A

volume left in lungs at end of normal expiration during quiet breathing

  • RV + ERV
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40
Q

What is minute ventilation?

A

volume of air moved between lungs and air per minute

  • measured by using amount of air expired per minute
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41
Q

T/F: all gas from minute ventilation participates in gas exchange

A

F because tidal volume is distributed between conducting airways and alveoli

  • some areas in conducting airways don’t participate in gas exchange
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42
Q

What is the anatomical dead space?

A

air within conducting airways that doesn’t participate in gas exchange

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43
Q

What is the physiological dead space?

A

total volume of gas in each breath that doesn’t participate in gas exchange

  • includes anatomical dead space and alveolar spaces that aren’t perfused
44
Q

What is alveolar ventilation?

A

volume of air that participates in gas exchange

45
Q

What is the most important variable in gas exchange?

A

alveolar ventilation

46
Q

What is the relationship between minute and alveolar ventilation if expired ventilation is constant?

A
  • inverse relationship with dead space volume and alveolar ventilation
  • increase in frequency -> decrease in alveolar ventilation
  • decrease in tidal volume -> decrease in alveolar ventilation
47
Q

T/F: air going to exchange areas is uniformly distributed

A

F, gravity affects it by increasing air to alveoli in lower portion of the lungs

48
Q

Lung function is determined by which 4 factors?

A
  • strength of chest and abdominal muscles
  • lung size
  • airway resistance
  • lung compliance
49
Q

How does strength of chest and abdominal muscles affect lung function?

A

decrease in strength -> reduction of inspiratory capacity

50
Q

How does lung size affect lung function?

A

decrease in areas involved in perfusion -> reduction of TLC

51
Q

How does airway resistance affect lung function?

A

increase in resistance -> airflow impaired

52
Q

How does lung compliance affect lung function?

A

stiffening of alveoli -> greater effort needed to inflate lungs

53
Q

Where is the major site of airway resistance?

A

large and medium sized bronchi b/c air has more leeway in how it travels

54
Q

Gas flow in larger airways is turbulent or calm?

A

turbulent

55
Q

When does turbulence occur?

A
  • at high flow rates
  • diameters change
56
Q

An increase in turbulence leads to…

A
  • increase in resistance
  • decrease in flow
57
Q

Small airways contribute to airway resistance via…

A
  • small diameter
  • large number of them
  • high airflow velocity
  • laminar flow
58
Q

T/F: there are no breath sounds in small airways

A

T, because they have laminar flow

59
Q

Which factors contribute to airway resistance?

A
  • diameter: smaller = higher resistance
  • volume: higher the volume of airways = decrease in resistance
  • airway mucus: increase = increase in resistance
  • edema: increase in fluid = increase in resistance
60
Q

Regulation of the diameter of airways are under…

A

ANS control

61
Q

What happens during PNS innervation of bronchial and bronchiolar smooth muscle?

A
  • contraction
  • increase in mucus production
  • Ach to M3 receptors associated with PLC
62
Q

What happens during SNS innervation of bronchial and bronchiolar smooth muscle?

A
  • relaxation
  • decrease in mucus production
  • norepi to beta 2 receptors
63
Q

Examples of bronchoconstrictors:

A
  • histamine
  • thromboxane
  • PGF2 alpha
  • leukotrienes
64
Q

Bronchoconstrictors are triggered by…

A

allergens and infections

65
Q

Examples of bronchodilators:

A
  • beta agonists: isoproterenol and epi (same effect as SNS)
  • M antagonists: atropine (inhibit Ach)
66
Q

What is distensibility of the lung?

A

how easily a lung can be stretched or inflated

67
Q

What is the elastic recoil of lungs?

A

ability to return back to original shape after being stretched - inversely related to lung compliance

68
Q

What happens if your lungs have a large lung compliance?

A

lung easily distensible, but difficult to deflate because of low elastic recoil

69
Q

What happens if your lungs have a small lung compliance?

A

stiff lung

  • difficult to inflate but easy to deflate because of high elastic recoil
70
Q

Lung compliance is often affected by…

A

respiratory disorders

71
Q

How do obstructive diseases affect lung compliance?

A

lung is more compliant due to loss of elastic recoil

  • easy to inflate but needs effort to get air out
  • high FRC because of high RV
72
Q

Examples of obstructive diseases:

A
  • emphysema
  • chronic bronchitis
  • cystic fibrosis
  • asthma
73
Q

How do restrictive diseases affect lung compliance?

A

lung is noncompliant

  • difficult to inflate, but easily deflatable
  • lower TLC but normal RV
74
Q

Examples of restrictive diseases:

A
  • scar tissue from infections
  • pulmonary fibrosis
75
Q

What is the relationship between surface tension and compliance?

A

increase in surface tension = decrease in compliance

76
Q

Surface tension occurs at…

A

inner surface of alveoli because of moist surface and spherical shape

  • smaller alveoli have greater pressure than larger alveoli
77
Q

What happens to the alveoli when there is an increase in surface tension?

A
  • air gets diverted to larger alveoli and causes them to overinflate
  • smaller alveoli collapse
78
Q

How do you reduce surface tension?

A

have type 2 cells produce surfactant

  • gets stimulated by stretching of alveoli when tidal volume is high
79
Q

What causes respiratory distress syndrome (RDS)?

A

inadequate surfactant production

80
Q

What happens to compliance during exercise?

A
  • compliance is higher
  • tidal volume increases and stimulates surfactant release
81
Q

What are some ways MDs can measure the efficiency of the respiratory system?

A
  • RV/TLC
  • forced vital capacity (FVC)
  • forced vital capacity in 1 sec (FEV1)
  • FEV1/FVC x 100
82
Q

What is the purpose of RV/TLC?

A

ratio used to distinguish different types of pulmonary disease

83
Q

What is the normal ratio for RV/TLC?

A

0.20

84
Q

How do you know if you have an obstructive disease by looking at RV/TLC?

A

increase in RV because of air being trapped secondary to airway collapse

85
Q

How do you know if you have a restrictive disease by looking at RV/TLC?

A

decrease in TLC

86
Q

What is forced vital capacity (FVC)?

A

volume that’s exhaled forcefully and rapidly after max inhalation

  • normally 5L
87
Q

Which test is the most useful for testing lung function?

A

FVC

88
Q

FVC for athletes?

A

> 7L

89
Q

FVC for people with asthma?

A

< 5L because of collapse of small airways

90
Q

FVC for people with bronchitis?

A

3 L because airways are swollen and inhibit air flow

91
Q

What happens during forced vital capacity in 1 sec (FEV1)?

A

max flow occurs early and decreases progressively toward RV

92
Q

Is FEV1 effort dependent or independent?

A
  • dependent (proportional)
  • independent at lower volumes
93
Q

FEV1/FVC x 100 corrects for…

A

differences in lung size

94
Q

What is the normal FEV1/FVC x 100 ratio?

A

80% is exhaled in a second

95
Q

What is the FEV1/FVC x 100 during obstructive diseases?

A

all measurements are reduced (FEV1, FVC, FEV1/FVC)

96
Q

What is the FEV1/FVC x 100 during restrictive diseases?

A

normal or slightly higher

  • FEV1 and FVC decreased
  • FEV1/FVC normal or high
97
Q

When does work increase during breathing patterns?

A
  • deeper breaths taken b/c has to overcome elastic properties of lung
  • respiration rate increases b/c needs greater flow resistance to overcome elastic properties of lung
98
Q

Label the red box:

A

Inspiratory reserve volume (IRV)

99
Q

Label the purple box:

A

expiratory reserve volume (ERV)

100
Q

Label the black box:

A

residual volume (RV)

101
Q

Label the gray box:

A

tidal volume (Vt)

102
Q

Label the orange box:

A

inspiratory capacity

103
Q

Label the green box:

A

vital capacity (VC)

104
Q

Label the yellow box:

A

functional residual capacity (FRC)

105
Q

Label the blue box:

A

total lung capacity (TLC)

Physiology (33 decks)

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