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2023 Systems Phys > Respiratory Mechanics > Flashcards

Respiratory Mechanics Flashcards

1
Q

To alter lung volumes we need:

A

Respiratory muscles to change size of thoracic cavity
Overcome tissue elastance (need to recoil)
Overcome surface tensionwithin alveoli

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2
Q

Which direction does air flow?

A

down the pressure gradient

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3
Q

When PA is less than PB…

PA - alveolar; PB - atmospheric

A

Air enters lung

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4
Q

When PA is greater than PB…

A

Air exits lungs

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5
Q

As volume increases, pressure exerted by gas…

Boyle’s Law

A

decreases

The pressure and volume of a gas are inversley related

Double volume, 1/2 pressure

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6
Q

How does Boyle’s Law work in us?

A

As the lungs expand in volume, P goes down
As the lungs shrink in volume, P goes up

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7
Q

How do respiratory muscles act on lungs?

A

Indirectly
Lungs and thoracic wall linked

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8
Q

How do muscles effect the thoracic cavity?

A

Muscles change the volume of the thoracic cavity

As cavity increases, lungs follow

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9
Q

Define

Inspiration

A

The active phase of breathing cycle

expending energy

Increase thoracic cavity volume
Decrease alveolar and intrapleural pressre

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10
Q

What is happening in the thoracic cavity before inspiration?

A

Respiratory muscles are relaxed
No air is flowing, PA=PB

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11
Q

What needs to happen in the thoracic cavity in order for air to move?

A

Lung volume has to change

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12
Q

What occurs in the thoracic cavity during inspiration?

A

Motor impulses from brainstem activate muscle contraction
Thoracic cavity expands - PA and Pip drop
Intrapleural pressure drops by association when thoracic cavity volume increases

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13
Q

What is happening during inspiration when PA drops?

A

Fresh air flows in until pressures are equalized

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14
Q

What happens during inspiration when Pip drops?

A

Increase in transpulmonary pressure gradient

needed to overcome increases elastic recoil force of stretched lungs

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15
Q

Diaphragm

A

The major muscle of inspiratory effect
Sheet of skeletal muscle forms floor

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16
Q

Diaphrgam when relaxed:

A

Dome shape protrudes upward into throax

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17
Q

Diaphragm when contracted:

A

It increases thoracic cavity by descending downward

Innervated by phrenic nerve

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18
Q

Diaphragm movement during normal inspiration…

A

moves 1 cm

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19
Q

Diaphragm movement during forced inspiration…

A

Diaphragm can move 10cm

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20
Q

Muscles of Inspiration

External Intercostal Muscles

What do they do? How do they work?

Run between ribs

A

Responsible for 25% of inspiratory effort:
Lie on top of internal intercoastal
Activated b intercostal nerves
Contaction: elevate ribs and thus sternum

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21
Q

Muscles of Inspiration

External Intercostal Muscles: Pump Handle Movement

A

Increasing interior/posterior pressure

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22
Q

Muscles of Inspiration

Accessory Muscles

What do they do?

A

Assist with forced inspiration eg, exercise

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22
Q

Muscles of Inspiration

External Intercostal Muscles: Bucket Handle Movement

A

Increasing transverse volume

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23
Q

Muscles of Inspiration

What are the two types of accessory muscles?

A

Scalene Muscles: elevated the first 2 ribs
Sternocleidomastoid Muscle: raises sternum

cause even greater drops in PA and Pip

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24
Q

Use of accessory muscles for inspiration is a sign of…

A

respiratory distress

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25
Q

What is the driving pressure for airflow in to the lungs?

A

Decreasing alveolar pressure

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26
Q

What initially creates the driving pressure for airflow into the lungs?

A

Increases thoracic cavity volume/lungs

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27
Q

Why does alveolar pressure decrease and then swing back up, but pleural pressure decreases continuously during inspiration?

A

Alveolar pressure comes back up because it is in communication with outside world
Intrapleural content decreases because it has no outside communication

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28
Q

The act of inhaling is _ ventilation

A

negative-pressure

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29
Q

Define

Expiration

What is it?

A

The passive phase of the breathing cycle
No energy

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30
Q

What occurs during Expiration?

A

Inspiratory muscles relax
Lungs recoil due to elastic properties
Pleural and alveolar pressures rise
Gas flows passively out of lung due to elastic recoil

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31
Q

What are the muscles of active expiraton?

A

abdominal and intercostals

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32
Q

How does the body empty air more completely?

A

need to increase PA even more

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33
Q

How do you further increase PA to empty the lungs more completely?

A

Need more force than accomplished by simple relaxation
Exercise or disease states (asthma)

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34
Q

What effect does contraction of abdominal wall and internal intercostals cause?

A

increasing intra-abdominal pressure

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35
Q

When is it difficult/unable to expand the lungs?

A

Scar tissue
Reduced surfactant
Mucous
Fluid

Hard to increase volume, difficult to decrease pressure and breath in

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36
Q

When is the lung unable to contract?

A

Emphysema - destroyed alveoli and elastic tissue

Hard to decrease volune, difficult to increase pressure and breath out

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37
Q

What are the 2 major patterns of gas flow?

A

Laminar
Turbulent

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38
Q

Define

Laminar flow

A

Air flows in same direction
parallel to walls
low flow rates
gas in center travels most rapidly

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39
Q

Define

Turbulent Flow

A

As air flow rate increases - air moves irregularly
Creates resistance to flow which requires higher pressure

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40
Q

How do you change turbulent flow?

A

Increases drive in pressure

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41
Q

Turbulence is most likely to occur when…

A

Average velocity is high and radius is large

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42
Q

Gas flow in larger airways is…

A

turbulent

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43
Q

Breath sounds heard with stethoscope are due to…

A

turbulent flow
Laminae is silent

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44
Q

What causes airflow?

A

Normal airways offer such low resistance, that only very small pressure gradients needed for adequate airflow

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45
Q

Poiseuille’s Law of Resistance for laminar flow:

A

R = 8+L+n/3.14r

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46
Q

Where is the cheif site of airway resistance?

A

Medium sized bronchi

47
Q

Airway resistance

Large airways have _ flow but large _

A

Decreases but vast cross sectional area and in parallel

48
Q

Define

Lung Volume

A

How much air is in the lungs

49
Q

Lung Volume

Diameter of airways change with…

A

lung volume

50
Q

Lung Volume

How does airway diameter change with Lung Volume?

A

Airways are supported by radial traction nof surrounding lung connective tissue
As lung expands, it pulls open airways
As lung volume decreases, smaller airways may be compressed at low lung volumes (increasing R)

51
Q

What assists in contraction of airways?

A

Bronchial smooth muscle tone increasing resistannce

52
Q

Bronchoconstriction

A

Decreases radius and increase resistance to airflow

53
Q

What are the major control factors of bronchoconstriction?

A

Neural Control: PNS
Local Control: Decreases CO2

Patholigical factors can produce bronchoconstriction (allergies, asthma)

54
Q

Neural control of bronchoconstriction

A

During quiet relaxed situations demand not high

ACh on muscarinic receptors

Many inhalers block ACh to prevent constriction

55
Q

Bronchiole pathway

relation of blood flow and airflow

A

Small blood flow -> decrease CO2 area -> Increase contraction of local-airway smooth muscle -> constriction of local airways -> increase airway resistance -> decrease airflow -> helps balance large airflow

56
Q

Airflow influences _ radius

A

airway

57
Q

Blood flow influences _ radius

A

vascular

58
Q

Pulmonary vascular Smooth Muscle pathway

relation of blood flow and airflow

A

Small blood flow -> Increased O2 in area -> relaxation of local pulmonary arteriolar smooth muscle -> dilation of local blood vessels -> decreases vascular resistance -> increase blood flow -> helps balance Large airflow

59
Q

Bronchodilation

A

Increase radius, decrease resistance to airflow

60
Q

What are the major control factors of bronchodilation?

A

Hormonal: EPI
Local Control: Increasing CO2

neural factors have minimal effect: SNS

61
Q

How does hormonal control effect bronchodilation?

A

EPI when demand is high, bind Beta-2 adrenergic agonists to increase airway radius

62
Q

How does gas density affect airway resistance?

A

Elevated gas density increases resistance

deep sea diving

63
Q

How does forced expiration affect airway resistance?

A

Airway compression increases resistance

64
Q

How does bronchial smooth muscle tone affect resistance?

A

Contraction of airways increases resistance

65
Q

How does lung volume affect resistance?

A

As lung volume decreases, resistance increases

66
Q

Forced Expiration

In normal breathing, resistance…

A

Doesn’t change much
Pip is less than airway pressure; airways open

67
Q

During forced expiration, resistance…

A

significantly inceases

68
Q

Forced expiration

AS elastic recoil decreases…

what happens to PA

A

PA decreases

69
Q

When does exhaling air lose pressure?

A

When it hits R

70
Q

Equal Pressure Point (EPP)

A

The point when Pairway = Pip

71
Q

If Pip is greater than Pairway….

What can occur?

A

collapse can occur

72
Q

How does EPP prevent lung collapse?

A

In healthy lungs, the EPP occurs normally where cartilage is present and prevents closure of the airway

73
Q

Why do the first four generations of the conducting zone contain alot of cartilage?

A

They ae subject to negative and positive pressures, the cartilage prevents collapse of the lung due to the changing pressures

74
Q

Forced Inspiration

What causes emphysema?

A

The loss of alveoli and thus elastic recoil, lowers PA further during forced expiration
EPP occurs closer to the alveoli, where the cartilage cannot prevent airway collapse

75
Q

What is the result of emphysema?

A

More air is trapped in the lungs

76
Q

EPP is influenced by…

A

Lung elastic recoil

77
Q

In a healthy lung, EPP sequence:

A

Recoil -> increasing PA-> EPP established in larger airways; collapse is minimal

78
Q

In emphysema, EPP sequence is:

A

Low recoil -> decreasinig PA -> EPP established in small airways; easily compressed

79
Q

Define

Chronic Obstructive Pulmonary Disease (COPD)

A

Umbrella term used to describe chronic lung diseases that cause limitations in lung airflow -> increases resistance

When R increases, larger pressure gradient needed to maintain normal flow rate

80
Q

COPD causes what changes in the respiratory system?

A

Alveoli lose their ability to recoil
Alveolar walls are destroyed
Airway walls become thickened and inflamed
Airways become clogged with mucus

81
Q

What are the two main forms of COPD?

A

Chronic Bronchitis
Emphysema

82
Q

Define

Pulmonary Function Tests

What are they?

A

A series of tests that evaluate how well lungs are working

83
Q

What are pulmonary function tests used for?

A

To differentiate and monitor lung diseases

Is SOD due to worsening emphysema or new heart failure?
Is cough due to emphysema or asthma?

84
Q

Types of PFTs

Spirometry

A

1st test performed
Compare measured values with normal values from population studies

85
Q

Lung volumes and capacities determine…

A

the amount (volume) of air someone can move in and out

seen on Volume-time curve

86
Q

Flow/Volume Loops

A

get more spirometry information
determine speed of flow

87
Q

What variables can impact lung function?

A

Age, height, weight, sex, race, disease/trauma

88
Q

How does the spirometry work?

A

Seated subject breathes into a closed system

Pneumotachometer

89
Q

What affect does emphysema have on residual volume?

A

It increases residual volume

90
Q

Define

Inspiratory Reserve Volume (IRV)

A

All we can inspire above a normal inspiration

91
Q

Define

Expiratory Reserve Volume (ERV)

A

Everything we are capable of exhaling

92
Q

Define

Inspiratory Capacity (IC)

A

Everything we can inspire

93
Q

Define

Residual Volume (RV)

A

All air trapped in our lungs no matter how hard you expire

Makes easier to move air in and out

94
Q

Define

Functional Residual Capacity (FRC)

A

All the air left over after a normal expiration

95
Q

Define

Vital Capacity (VC)

A

All air we can move out of lung in a single breath

96
Q

Define

Total Lung Capacity (TLC)

A

All air we can and cant move in and out during a single breath

97
Q

What is the average value of VT?

A

500 mL

98
Q

Equation

IC

A

IC = IRV + VT

99
Q

Equation

FRC

A

FRC = ERV + RV

100
Q

Equation

VC

A

VC = IRV + VT + ERV

101
Q

Equation

TLC

A

TLC = VC + RV

102
Q

What is the average value of VC?

A

4800 mL

103
Q

What is the average value of TLC?

A

6000 mL

104
Q

Lung function is divided into _ and their combinations give us…

A

4 volumes
4 Capacities

105
Q

Spirometry measures…

A

amount of air entering and leaving lungs

Can not provide info about absolute lung volumes (RV, FRC, TLC)

106
Q

What techniques are used to determine RV, FRC, and TLC?

A

Gas dilution
Body plethysmography

107
Q

What are the 2 types of dysfunctions yielding abnormal spirometry results?

A

Obstructive
Restrictive

108
Q

Obstructive Lung Disorders

How does it affect lung volumes and capacities ?

A

Decreases VC, IRV, ERV
Increases RV, FRC, TLC

109
Q

Obstructive Lung Disorders

A

Slow flow rates
Hyperinflation
Decreased recoil

decrease capacity to get air out

110
Q

What is the result of increased RV in obstructive lung disorders?

A

Air trapped
Barrel Chest

111
Q

What affect do restrictive lung disorders have on lung volumes and capacities?

A

Decreases VC, RV, FRC, VT, and TLC

112
Q

Restrictive Lung Disorders

A

Increase recoil
Decrease volume
Decrease capacity to get air in

113
Q

What is the result of decreased TLC in restrictive lung disorders?

A

Difficulty to expand

114
Q

What is an example of an Obstructive Lung Disorder?

A

COPD

115
Q

What is an example of a Restrictive Lung Disorders?

A

Pulmonary Fibrosis

2023 Systems Phys (41 decks)

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