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Pathophysiology (RESP 212) > Module 3 Respiratory Mechanics > Flashcards

Module 3 Respiratory Mechanics Flashcards

1
Q

What is Tidal Volume (Vt)

A

A relaxed breath.

Normal volume of both inhalation and exhalation

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2
Q

What is Total Lung Capacity?
(TLC)

A

Volume of air in your lungs at max inhalation

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3
Q

What is Vital Capacity (VC)?

A

Volume of air breathed out from max inhalation

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4
Q

What is Residual Volume (RV)?

A

Air left in the lungs after exhalation

(they never fully empty or collapse when normal)

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5
Q

What is Functional Residual Capacity (FRC)?

A

The volume of air left after a relaxed Vt exhalation.

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6
Q

Inspiratory Capacity (IC)?

A

What you can inhale from FRC

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7
Q

Expiratory Reserve Volume (ERV)?

A

what you maximally exhale from after Vt

everything you can exhale after a normal exhale

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8
Q

Inspiratory Reserve Volume (IRV)?

A

What you can inhale above your Vt
(everything you can take in after a normal breath)

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9
Q

What is the min volumes required for capacities?

A

2 or more volumes.

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10
Q

diagram of volume capacities.

A
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11
Q

Pressure Gradients?

A

Idk slide was blank, check later.

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12
Q

when there is no air movement (Static state)? Why is it considered FRC or why does it happen?

hint consider Hooke’s Law

A

FRC occurs because lungs recoil and the thorax pulls open in the opposite direction.

2 forces balance at FRC

  • Hooke’s law + elastic recoil =
    As elastic material is pulled, the recoil force increases
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13
Q

What is Elasticity?

A

The tendency of a stretched object to return to its original shape.

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14
Q

What are examples of elastic properties and relationships in the thorax?

Insert image of the lungs

A
  1. Elastic recoil of chest wall
    • Pleural pressure - pressure at surface of chest
  2. Elastic recoil of lung
    • Alveolar pressure - pleural pressure
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15
Q

What is the value for Airway opening pressure (Pao) and pleural pressure?

A

760 and 755 respectively.

note Pleural pressure is sub atmospheric;is determined from esophageal pressure

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16
Q

Do the thorax and lungs have a relationship regarding elasticity?

A

Yerp

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17
Q

Aside from lung/thorax interaction, What element helps keep the lungs open?

A

Surfactant.

It keeps the lungs open by decreasing surface tension. Decrease in ST prevents alveoli from sticking together so that they actually expand)

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18
Q

What needs to happen in the lungs to move air?

A

There needs to be a interaction with pressure, to be specific: Pressure gradients (work)

(air (fluids?) moves from high pressure to low pressure)

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19
Q

What is a dynamic condition in pressure gradients?

A

When airflow is present.

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20
Q

What are 3 types of pressure gradients?

A

Prs = Transairway/Transrespiratory pressure

PL = Transpulmonary pressure

Pw = Transthoracic pressure

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21
Q

Review slides regarding Respiratory system mechanics (2 slides).

“egans: Chapter 11, pg 227”

A
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22
Q

Lung - Thorax Pressure Gradients

What is Prs and why is it important?

A

Transairway pressure (Prs) is the difference between Alveolar pressure (PA) and ATM (Pao, pbs)

Prs = PA - Pao

This gradient is important because it causes air flow.

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23
Q

Lung Thorax Pressure Gradients:

What is PL, and what is its function?

A

Transpulmonary pressure (PL) describes the difference between Alveolar pressure (AP) and Pleural pressure (Ppl)

PL = PA - Ppl

Distending pressure across the alveolar walls

from google reps pressure that promotes air flow and distends (enlarge/swell by pressure) lungs*

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24
Q

Lung - Thorax Pressure Gradients

What is Pw, and why is it important?

A

Transthoracic/ Transmural pressure (Pw) is the pressure difference between the pleural space (Ppl) and atm pressure at body surface (Pbs)

Pw - Ppl - Pbs

Pressure difference across the thoracic wall

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25
What happens when Pw increases/decreases?
26
What is PO2?
Partial pressure of Oxygen It reps the amount of oxygen gas dissolved in the blood
27
Why is PO2 important in abgs?
It primarily measures the effectiveness of the lungs in pulling oxygen into the blood stream from the atmosphere.
28
What formula best describes TLC?
TLC = RV + ERV + Vt + IRV
29
Equation for VC?
VC = ERV + Vt + IRV measures only what you blow out.
30
Formula for FRC
RV + ERV Residual volume and expiration reserve volume
31
Equation for IC
Vt + IRV Tidal volume and inspiratory reserve volume
32
Expiration reserve volume (ERV)
33
What is the difference between volume and capacity?
Capacities are made up of 2 or more volumes.
34
Why do we have FRC?
We have FRC because lungs recoil and your thorax pulls open in the opposite direction. 2 forces balance at FRC
35
What aids FRC to keep the lungs open?
Surfactant. it keeps the lungs open by reducing surface tension.
36
At FRC, what state are the lungs in?
Static state. there is no air flow.
37
What needs to happen in the lungs to move air?
Thorax needs to have a pressure gradients work to move air (work).
38
How do pressure gradients help lungs move air?
Air (fluids) move from a state of high to low pressure.
39
What state is it when airflow is present
dynamic condition
40
ATM?
Pao Pressure at the airway opening of the resp system airway. i.e mouth, nose, tracheostomy opening, tubes, etc.
41
Barometric pressure?
Pbs Pressure measured at the body surface. -body surface pressure
42
pleural pressure
Ppl Pressure measured in the pleural space.
43
how do you measure changes in pleural measure?
they’re estimated by measuring pressure changes in esophagus
44
Alveolar Pressure
PA Pressure in the alveolar (gas space) regions of the lungs
45
Transairway/Tranrespiratory pressure. what does this gradient describe and cause?
PRS = PA - PAO The difference between ATM and alveolar pressure This gradient causes air flow
46
Transpulmonary pressure. what does it describe?
PL = PA - Ppl The pressure difference between alveolar pressure and pleural space -distending pressure across alveolar walls.
47
Transthoracic pressure
Pw = Ppl - Pbs Pressure difference across the thoracic wall (chest wall)
48
Pao/pbs
ATM pressure around the body
49
Pao
pressure at airway opening
50
Pbs
Pressure at the body surface
51
PA
Alveolar pressure
52
Ppl
Pressure within the pleural space
53
Prs
Transairway/transrespiratory pressure
54
PL
Transpulmonary pressure
55
Pw
Transthoracic/transmural pressure
56
What happens during inspiration?
Active contractions of ventilators muscles -Ppl decreases -PL (Pa-Ppl) decreases -Pa drops below Pao (boyles law) At end inspiration Prs = 0 -air flow ceases
57
What happens to Ppl during inspiration?
It decreases. Thoracic expansion (diaphragm drops) causes a increase in volume, which in turn, causes pressure to decrease
58
Why is a drop below Pao related to boyles law?
The pressure in lungs drop below ATM and air moves into the lungs. Pressure drops, volume (air) increases.
59
What happens during exhalation
ventilators muscles relax and diaphragm moves back up - passive recoil forces cause lungs to shrink PA increase PA increases above Pao Air flows out lungs down pressure gradient At end expiration Prs = 0 -air flow ceases
60
Exhalation: describe the PA change.
PA increases and lung volume decreases. When volume decreases, there’s a increase in pressure.
61
Exhalation, what does boyles law sugggest?
The pressure in lungs is higher than atmosphere forcing air out.
62
What happens to Transthoracic pressure (Pw) during inspiration?
Overall, its always under negative pressure. It becomes more negative during inspiration than comes back.
63
Describe thoracic pressure during inspiration?
When pressure increases in the thoracic cavity (inspiration), it pushes the chest wall out even more and causes a increase in pressure in the pleural space making it negative.
64
What forces are needed need to be overcome so air can move in and out of the lungs?
Elastance Compliance Resistance
65
Compliance (CL)
Measure of how easy it is to change lunge volume Basically, How likely is something to inflate when you put pressure on it
66
CL FORMULA?
Change in volume/ change in pressure Normal CL = 0.2L
67
What is the opposite of CL?
Elastance (1/elastance)
68
Do ventilators change compliance numbers?
no.
69
What does high compliance infer?
Lungs are easier to inflate. ventilators don’t put enough pressure to reach tidal volume
70
What does low compliance infer?
Lungs are harder to inflate. Ventilators are putting in a lot of pressure to reach tidal volume
71
What relation does pulmonary fibrosis have to compliance?
Pulmonary fibrosis causes the lungs to be stiff and thus harder to inflate
72
What forces are needed to overcome for air to move in and out of the lungs?
1. Elastance/Compliance 2. Airway Resistance
73
If Elastance = lung recoil force. What does compliance (CL) imply if it is high or low?
Compliance = how stiff (change in lung volume by the change in pressure, in the presence of flow.) Increased = too pliable Decreased = too stiff
74
Dynamic vs static compliance?
Dynamic = compliance during breathing (airflow) Static = compliance when airflow is absent. (like inspiratory pause).
75
Low lung elasticity requires what to change the volume of the lungs?
Greater than average intrapleural pressure
76
High lung compliance would indicate what to change the volume of the lungs?
little pressure difference in intrapleural pressure.
77
Lung compliance is defined as?
The ability of the lungs and pleural cavity to change in volume based on changes in pressure.
78
Two factors that determine lung complinace?
Elasticity of the lung tissue and surface tension at air water interfaces
79
Which lung diseases would be associated with low lung compliance?
Restrictive lung diseases. Anything that makes it harder for the lungs to expand/deflate, or where gas exchange is impaired. i.e pulmonary fibrosis.
80
Which diseases would you associate with high lung compliance?
Obstructive diseases i.e emphysema = destruction of elastic tissue of lungs
81
Elastance/compliance is effected by?
1. Elastic recoil from elastin/collagen 2. surface tension affected by surfactant. 3. conditions of the thorax 4. volume in the lungs
82
Resistance (Raw) is produced by frictional resistance to gas flow, where specifically would this be seen?
Friction between: -gas molecules -gas and tube walls
83
2 types of flow
Laminar flow (less resistance) Turbulent flow (more resistance)
84
Where would you find Laminar flow?
smaller airways (bronchioles and distal airspaces)
85
Where would you find Turbulent flow?
Upper airways (trachea and bronchi)
86
Is Laminar or Turbulent flow faster?
Laminar is faster due to lower resistance
87
Poiseuille's law pertains to what? V = ∆Pπ r^4 / 8Ln
Laminar flow If you reduce your radius by half, you would need a 16 fold increase in pressure to maintain flow.
88
Factors of Poiseuille's law?
Change in pressure Radius of the tube Length of the tube Viscosity of the fluid
89
How to calculate resistance?
Resistance = change in pressure/flow rate
90
How to calculate compliance?
Change in volume/change in pressure
91
When is positive pressure and negative pressure seen in relation to mechanical ventilation?
Positive pressure is used to deliver a breath, whereas normal physiological breath requires negative pressure to draw air in.
92
Left off at slide 58
93
What does Poiseuille's law depict on airways during inspiration?
airways are pulled open, availing wider radius within airways.
94
Exhalation mechanics: what happens?
Airways narrow, requiring faster airflow.
95
What is cephalad airflow bias?
When flow increases in speed because of narrowing airways. It aids in secretion clearance.
96
What is Equal pressure point (EPP)
Basically collapse of airways. When airways cannot keep themselves open as a result of the pleural pressure equating with intra-airway pressure.
97
What is a primary sign of concern with obstructive lung diseases like asthma or emphysema?
Air trapping.
98
What is air trapping?
The inability to exhale air that is trapped secondary to resistance/compliance change.
99
How to improve work of breathing (WOB)
1. improve pulmonary mechanics (via meds, cpap) 2. Take over the WOB (mechanical ventilation)

Pathophysiology (RESP 212) (14 decks)

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