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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
Use of accessory muscles for inspiration is a sign of...
respiratory distress
25
What is the driving pressure for airflow in to the lungs?
Decreasing alveolar pressure
26
What initially creates the driving pressure for airflow into the lungs?
Increases thoracic cavity volume/lungs
27
Why does alveolar pressure decrease and then swing back up, but pleural pressure decreases continuously during inspiration?
Alveolar pressure comes back up because it is in communication with outside world Intrapleural content decreases because it has no outside communication
28
The act of inhaling is _ ventilation
negative-pressure
29
# Define Expiration | What is it?
The passive phase of the breathing cycle No energy
30
What occurs during Expiration?
Inspiratory muscles relax Lungs recoil due to elastic properties Pleural and alveolar pressures rise Gas flows passively out of lung due to elastic recoil
31
What are the muscles of active expiraton?
abdominal and intercostals
32
How does the body empty air more completely?
need to increase PA even more
33
How do you further increase PA to empty the lungs more completely?
Need more force than accomplished by simple relaxation Exercise or disease states (asthma)
34
What effect does contraction of abdominal wall and internal intercostals cause?
increasing intra-abdominal pressure
35
When is it difficult/unable to expand the lungs?
Scar tissue Reduced surfactant Mucous Fluid | Hard to increase volume, difficult to decrease pressure and breath in
36
When is the lung unable to contract?
Emphysema - destroyed alveoli and elastic tissue | Hard to decrease volune, difficult to increase pressure and breath out
37
What are the 2 major patterns of gas flow?
Laminar Turbulent
38
# Define Laminar flow
Air flows in same direction parallel to walls low flow rates gas in center travels most rapidly
39
# Define Turbulent Flow
As air flow rate increases - air moves irregularly Creates resistance to flow which requires higher pressure
40
How do you change turbulent flow?
Increases drive in pressure
41
Turbulence is most likely to occur when...
Average velocity is high and radius is large
42
Gas flow in larger airways is...
turbulent
43
Breath sounds heard with stethoscope are due to...
turbulent flow Laminae is silent
44
What causes airflow?
Normal airways offer such low resistance, that only very small pressure gradients needed for adequate airflow
45
Poiseuille's Law of Resistance for laminar flow:
R = 8+L+n/3.14r
46
Where is the cheif site of airway resistance?
Medium sized bronchi
47
# Airway resistance Large airways have _ flow but large _
Decreases but vast cross sectional area and in parallel
48
# Define Lung Volume
How much air is in the lungs
49
# Lung Volume Diameter of airways change with...
lung volume
50
# Lung Volume How does airway diameter change with Lung Volume?
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
What assists in contraction of airways?
Bronchial smooth muscle tone increasing resistannce
52
Bronchoconstriction
Decreases radius and increase resistance to airflow
53
What are the major control factors of bronchoconstriction?
Neural Control: PNS Local Control: Decreases CO2 | Patholigical factors can produce bronchoconstriction (allergies, asthma)
54
Neural control of bronchoconstriction
During quiet relaxed situations demand not high | ACh on muscarinic receptors ## Footnote Many inhalers block ACh to prevent constriction
55
Bronchiole pathway | relation of blood flow and airflow
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
Airflow influences _ radius
airway
57
Blood flow influences _ radius
vascular
58
Pulmonary vascular Smooth Muscle pathway | relation of blood flow and airflow
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
Bronchodilation
Increase radius, decrease resistance to airflow
60
What are the major control factors of bronchodilation?
Hormonal: EPI Local Control: Increasing CO2 | neural factors have minimal effect: SNS
61
How does hormonal control effect bronchodilation?
EPI when demand is high, bind Beta-2 adrenergic agonists to increase airway radius
62
How does gas density affect airway resistance?
Elevated gas density increases resistance | deep sea diving
63
How does forced expiration affect airway resistance?
Airway compression increases resistance
64
How does bronchial smooth muscle tone affect resistance?
Contraction of airways increases resistance
65
How does lung volume affect resistance?
As lung volume decreases, resistance increases
66
# Forced Expiration In normal breathing, resistance...
Doesn't change much Pip is less than airway pressure; airways open
67
During forced expiration, resistance...
significantly inceases
68
# Forced expiration AS elastic recoil decreases... | what happens to PA
PA decreases
69
When does exhaling air lose pressure?
When it hits R
70
Equal Pressure Point (EPP)
The point when Pairway = Pip
71
If Pip is greater than Pairway.... | What can occur?
collapse can occur
72
How does EPP prevent lung collapse?
In healthy lungs, the EPP occurs normally where cartilage is present and prevents closure of the airway
73
Why do the first four generations of the conducting zone contain alot of cartilage?
They ae subject to negative and positive pressures, the cartilage prevents collapse of the lung due to the changing pressures
74
# Forced Inspiration What causes emphysema?
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
What is the result of emphysema?
More air is trapped in the lungs
76
EPP is influenced by...
Lung elastic recoil
77
In a healthy lung, EPP sequence:
Recoil -> increasing PA-> EPP established in larger airways; collapse is minimal
78
In emphysema, EPP sequence is:
Low recoil -> decreasinig PA -> EPP established in small airways; easily compressed
79
# Define Chronic Obstructive Pulmonary Disease (COPD)
Umbrella term used to describe chronic lung diseases that cause limitations in lung airflow -> increases resistance ## Footnote When R increases, larger pressure gradient needed to maintain normal flow rate
80
COPD causes what changes in the respiratory system?
Alveoli lose their ability to recoil Alveolar walls are destroyed Airway walls become thickened and inflamed Airways become clogged with mucus
81
What are the two main forms of COPD?
Chronic Bronchitis Emphysema
82
# Define Pulmonary Function Tests | What are they?
A series of tests that evaluate how well lungs are working
83
What are pulmonary function tests used for?
To differentiate and monitor lung diseases ## Footnote Is SOD due to worsening emphysema or new heart failure? Is cough due to emphysema or asthma?
84
# Types of PFTs Spirometry
1st test performed Compare measured values with normal values from population studies
85
Lung volumes and capacities determine...
the amount (volume) of air someone can move in and out | seen on Volume-time curve
86
Flow/Volume Loops
get more spirometry information determine speed of flow
87
What variables can impact lung function?
Age, height, weight, sex, race, disease/trauma
88
How does the spirometry work?
Seated subject breathes into a closed system | Pneumotachometer
89
What affect does emphysema have on residual volume?
It increases residual volume
90
# Define Inspiratory Reserve Volume (IRV)
All we can inspire above a normal inspiration
91
# Define Expiratory Reserve Volume (ERV)
Everything we are capable of exhaling
92
# Define Inspiratory Capacity (IC)
Everything we can inspire
93
# Define Residual Volume (RV)
All air trapped in our lungs no matter how hard you expire | Makes easier to move air in and out
94
# Define Functional Residual Capacity (FRC)
All the air left over after a normal expiration
95
# Define Vital Capacity (VC)
All air we can move out of lung in a single breath
96
# Define Total Lung Capacity (TLC)
All air we can and cant move in and out during a single breath
97
What is the average value of VT?
500 mL
98
# Equation IC
IC = IRV + VT
99
# Equation FRC
FRC = ERV + RV
100
# Equation VC
VC = IRV + VT + ERV
101
# Equation TLC
TLC = VC + RV
102
What is the average value of VC?
4800 mL
103
What is the average value of TLC?
6000 mL
104
Lung function is divided into _ and their combinations give us...
4 volumes 4 Capacities
105
Spirometry measures...
amount of air entering and leaving lungs ## Footnote Can not provide info about absolute lung volumes (RV, FRC, TLC)
106
What techniques are used to determine RV, FRC, and TLC?
Gas dilution Body plethysmography
107
What are the 2 types of dysfunctions yielding abnormal spirometry results?
Obstructive Restrictive
108
Obstructive Lung Disorders | How does it affect lung volumes and capacities ?
Decreases VC, IRV, ERV Increases RV, FRC, TLC
109
Obstructive Lung Disorders
Slow flow rates Hyperinflation Decreased recoil | decrease capacity to get air out
110
What is the result of increased RV in obstructive lung disorders?
Air trapped Barrel Chest
111
What affect do restrictive lung disorders have on lung volumes and capacities?
Decreases VC, RV, FRC, VT, and TLC
112
Restrictive Lung Disorders
Increase recoil Decrease volume Decrease capacity to get air in
113
What is the result of decreased TLC in restrictive lung disorders?
Difficulty to expand
114
What is an example of an Obstructive Lung Disorder?
COPD
115
What is an example of a Restrictive Lung Disorders?
Pulmonary Fibrosis

2023 Systems Phys (41 decks)

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