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BRS (RF) > Cardioresp mechanics > Flashcards

Cardioresp mechanics Flashcards

1
Q

What is inspiration?

A

The process that facilitates the movement of air to enter into the lungs

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2
Q

What is expiration?

A

Process that causes air to be expelled from the lungs

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3
Q

What are the two main muscle groups for inspiration?

A

Diaphragm

External intercostal muscles

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4
Q

What comprises a respiratory cycle?

A

One sequence of inspiration and expiration

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5
Q

During inspiration what happens to the diaphragm?

A

Diaphragm contracts, pulls inferiorly towards the abdominal cavity resulting in a larger thoracic cavity-> Increases volume subsequently decreases the intrathoracic pressure

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6
Q

What happens to the external intercostal muscles during inspiration?

A

Contracts
Ribs move outwards and upwards, causing ribcage expansion to increase the thoracic cavity volume
Lung stretches and expands, decreasing the inter alveolar pressure, the pressure gradient enables air to move into the lungs

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7
Q

How happens during expiration?

A

Expiration is passive
Elasticity of the lung tissues causes lung recoil -> Diaphragm and intercostal muscles relax following inspiration
Thoracic cavity and lungs decrease volume to increase the interpulmonary pressure > atmospheric pressure.
Pressure gradient causes air to leave lungs

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8
Q

What is the protocol for conducting a pulmonary function test?

A

1) Patient wears nose clip
2) Patient wraps lips rounds mouthpiece
3) Patient completes at least one tidal breath
4) Patient inhales steadily to total lung capacity
5) Patient exhales as hard and fast as possible
6) Exhalation continues until residual volume is reached
7) Patient immediately inhales to TLC
8) Visually inspect performance and volume time curve,

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9
Q

In obstructive diseases in which direction does displacement occur along the x-axis of normal flow volume loops?

A

Left displacement

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10
Q

In restricted diseases in which direction does x-axis directional displacement occur on a pressure flow volume loop?

A

Right displacement

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11
Q

What are the main features on an obstructive pressure flow volume loop?

A

Indentation (coving) on pressure volume loop.
The expiration curve is indented
The TLC is minimally changed

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12
Q

In restrictive disease why is the pressure volume loop narrower?

A

Restrictive diseases reduces the capacity within the lungs

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13
Q

In an extrathoracic obstruction which curve is blunted?

A

The inspiratory curve is bounded

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14
Q

Why is the inspiratory curve blunted for an extra-thoracic obstruction?

A

Inspiration displaces tumour, obstruction favourable in the direction that covers the trachea
EXPIRATION NORMAL
Impedes airflow into the lungs

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15
Q

A blunted expiratory curve in a flow volume loop is associated with which type of obstruction?

A

Intrathoracic obstruction

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16
Q

Why is there expiratory blunting in an intrathoracic obstruction”?

A

Does not impeded inspiration however expiration is significantly reduced, forced expiration obstructs airflow

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17
Q

How does COPD affect flow volume loops?

A

COPD curve shifted to the left, considering the lungs are filled with air initially -> Greater residual volume
Narrower airways –> Lower peak, & coving of curve

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18
Q

What is Poiseuilles law? (Equation)

A

𝑹𝒆𝒔𝒊𝒔𝒕𝒂𝒏𝒄𝒆= 𝟖𝜼𝒍/(𝝅𝒓^𝟒 )

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19
Q

What relationship can be established between resistance and radius?

A

Considering that length and viscosity of liquid is constant, it can be assumed that resistance is inversely proportion to (Radius)^4

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20
Q

What is the relationship established for Boyle’s Law?

A

Pressure of a gas is inversely proportional to its volume

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21
Q

How are small airway radii compensated in terms of airflow?

A

Smaller the calibre of airways, radius is reduced  Greater resistance. However it is important to consider flow  low flow through a small tube, and high flow through large tube  Greater resistance in high flow environment.

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22
Q

How does the trachea accommodates for reduced radius?

A

Trachea bifurcates into primary bronchi  Bronchioles  Flow significantly decreases (accommodating reduced radius)  minimises resistance.

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23
Q

Which airway generation results in peak resistance?

A

Fourth generation

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24
Q

What is conductance?

A

Ability for airways to conduct and enable air to pass through, this increases with increasing lung volume - decreases resistance

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25
Q

During inspiration how does resistance decrease?

A

During inspiration intrathoracic and and airway expansion occurs - airway radius increases therefore decreasing resistance

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26
Q

Which muscle regulates the diameters and resistance of arterioles and small arteries?

A

Smooth muscle

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27
Q

What happens to pressure across circulation?

A

The pressure declines across the circulation due to vicious (frictional) pressure losses) - small arteries and arterioles present majority of resistance to flow.

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28
Q

What is the MAP calculation relating cardiac output?

A

MAP = CO X PVR

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29
Q

What are the assumptions for equating mean arteriole pressure with cardiac output x PVR?

A

Laminar flow
Rigid vessels
Right atria, pressure is negligible
Blood can be directed by specific contraction and relaxation of the blood vessels that supply particular vascular bed required

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30
Q

What are the three main variables of blood flow resistance?

A 
Fluid viscosity (n): Not fixed but in most physiological conditions, this remains approximately constant 
Length of the tube (Fixed) - length of blood vessels remains constant 
Inner radius of tube (R), variable, and the main determinant of resistance
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31
Q

During exercise vasodilation and vasoconstriction causes blood flow diversion into which muscle?

A

Skeletal muscle

32
Q

What does laminar flow mean?

A

Blood flows in discrete current lines with minimal interference with each other -> laminated flow

33
Q

Can laminar flow be auscultated?

A

No.

34
Q

Describe the velocity of fluid in laminar flow?

A

Velocity of the fluid is constant at any one point, flowing in layers.
Blood flows fastest closest to the centre of the lumen

35
Q

Where in the lumen does blood flow fastest during laminar flow?

A

Blood flows faster in the centre of the lumen

36
Q

Why is the cuff pumped in order to calculate blood pressure measurement?

A

Obstructs flow, releasing the cuff slowly results in blood flowing through the cuff producing turbulent flow, sounds of Korotkoff

37
Q

What sounds are heard during blood pressure readings?

A

Sounds of Korotkoff

38
Q

How is turbulent flow achieved during blood pressure readings?

A

Partial vascular occlusion results in turbulent flow, causing slow tapping sound.

39
Q

Why does the sound disappear during blood pressure readings, as the pressure applied is reduced?

A

Decreasing the pressure significant will result in reduced sounds considering the occlusion is removed, enabling blood to flow in a laminar fashion

40
Q

What does turbulent blood flow mean?

A

Characterised by whirlpool regions and velocity of fluid is not constant in turbulent flow whereas it is constant in laminar flow.

41
Q

What currents are formed in turbulent flow?

A

Eddy’s currents, blood flows erratically, and is prone to accumulation

42
Q

What is turbulent flow associated pathophysiologically with?

A

Changes to the endothelial lining of the blood vessels, can alter the shear stress on vessels.

43
Q

Where is the blood pressure cuff usually applied?

A

Upper arm

44
Q

How high should the blood pressure increase when taking measurements?

A

Exceeds arterial pressure, place stethoscope distal to the cuff, blood occluded, no initial sounds

45
Q

When releasing the pressure on the blood cuff, what blood flow arises?

A

Turbulent blood flow

46
Q

What blood pressure is recorded when the sound appears upon bp measurements?

A

Systolic blood pressure

47
Q

What blood pressure is recorded upon sound disappearing during bp measurements?

A

Diastolic blood pressure

48
Q

What is pulse pressure?

A

The difference between systolic and diastolic blood pressure

49
Q

Why does the aortic pressure decrease slowly during diastole?

A

Due to arterial elasticity buffering pressure changes

50
Q

What is the dichroic notch?

A

Blood enters the aorta faster than it leaves. aortic valve closes therefore causing blood recoil.

51
Q

What are the four equations for calculation mean arterial pressure?

A

𝑀𝐴𝑃=1/3 𝑆𝐵𝑃+2/3 𝐷𝐵𝑃
𝑀𝐴𝑃=1/3 𝑃𝑃+𝐷𝐵𝑃
𝑀𝐴𝑃=𝑆𝐵𝑃 −2/3 𝑃𝑃
𝑀𝐴𝑃=𝑄 𝑥 𝑇𝑃𝑅

52
Q

What prevents the trachea from collapsing?

A

C-shaped cartilaginous rings

53
Q

What is patency?

A

Patency is whether the airways are open and active, and are able to allow air through

54
Q

What is a pre-inspiratory lung in terms of transmural pressure and patency?

A

The transmural pressure is positive , therefore the airway is patent

55
Q

What is a forced expiration in terms of capacities and volumes?

A

Forced expiration results in the total lung capacity to residual volume, there is a significant increase in intrapleural pressure.

56
Q

Why doe the airways collapse during a hard forced expiration?

A

Forced expiration  Total lung capacity to residual volume, there is a significant increase in intrapleural pressure. Pleural pressure > internal pressure of collapsible tubes  Airways close making forced expiration difficult.
During forced expiration the intrapleural pressure is significant, exerting an pressure inwards on the collapsible tube. Inwards pressure > outward pressure exerted by individual tubes  Collapse.

57
Q

What is compliance?

A

Compliance is the willingness of a structure to change shape when pressure is applied

58
Q

What is elastance?

A

Tendency for structure to recoil to original volume (opposite) -> Resistant to permanent structural change, reduced exhibition of plastic behaviour

59
Q

What is ventilation?

A

Pressure changes in relation to volume for inflation & deflation do not overlap. Therefore it is harder to inflate than to deflate

60
Q

In which circumstance is the lungs more compliant in comparison to air filled?

A

Fluid-filled

61
Q

What is the purpose of liquid surfactant in terms of surface tension?

A

Liquid surfactant lining the lungs, and the air-water interface exhibits surface tension whereas fluid-water interface does not exhibit surface tension.

62
Q

What is the importance of arterial compliance?

A

Aortic valve closure  Ejection from the left ventricle ceases, however due to elastic recoil exhibited by elastic arteries, the pressure declines at a reduced rate  Diastolic flow in downstream circulation.

63
Q

What is elastic recoil?

A

Principle of elastic recoil, the kinetic energy is stored within the elastic arteries of the tunica media, and subsequently can be reapplied to blood to maintain blood pressure within systemic circulation
Unidirectional flow during diastole

64
Q

How does the skeletal pump help with venous return?

A

The contraction of the muscles facilitates the movement of blood through the veins towards the heart, this decreases venous capacitance
Contraction and venous valves enables blood to flow unidirectionally

65
Q

What is the respiratory pump?

A

Intrathoracic pressure decreases during inspiration through increased intrathoracic volume.
Reduction in pressure provides a pressure potential for blood to return to the right atrium through the vena cava, this increases venous return

66
Q

How does the overcome gravity in terms of venous return?

A

Standing causes activation of the sympathetic nervous system  Vasoconstriction of veins  This increases total peripheral resistance and maintains blood pressure.
Standing increases heart rate, in addition to increasing the force of contraction, enabling more blood to return to the brain. Dysfunctional return mechanism  Syncope.

67
Q

How does varicosity and oedema form in terms of venous return?

A

incompetent valves causes dilated superficial veins within the leg (varicose legs)
Prolonged elevation of venous pressure - oedema in feet, despite intact compensatory mechanisms

68
Q

What is an aneurysmal disease?

A

Endothelial walls weaken over prolonged period of time -> distention

69
Q

What does the Law of Laplace associate with during aneurysmal disease?

A

Vascular aneursyms increase radius of the vessel, for the same internal pressure, the inward force exerted by the muscular wall increases.
Weakened muscle fibres, this form cannot adequately be produced to withstand the internal pressure, therefore the aneursym will continue expansion until eruption.

70
Q

What does the Law of Laplace associate with during aneurysmal disease?

A

Vascular aneursyms increase radius of the vessel, for the same internal pressure, the inward force exerted by the muscular wall increases.
Weakened muscle fibres, this form cannot adequately be produced to withstand the internal pressure, therefore the aneurysm will continue expansion until eruption.
REMINDER: TENSION = PRESSRE X RADIUS

71
Q

What is the Law of Laplace?

A

Tension = pressure x radius
Increasing radius, increases the tension of the wall (thickness must increase), prevents wall tension exceeding the tension capacity of vessel

72
Q

Where is the majority of circulating blood located?

A

Within the venous system

73
Q

Describe the relationship between venous compliance and arterial compliance at lower pressures?

A

Venous compliance is 10-20 times greater than arterial compliance at lower pressures.

74
Q

What is a venous reservoir?

A

Relatively small changes in venous pressure distend veins, and increase volume of blood stored within them. Gravity results in accumulation of blood in the legs due to venous capcitnce - reduced venous return- reduced EDV/Preload , and thus causes syncope.

75
Q

How is postural hypotension overcome?

A

Venous constriction more blood returned to her and cardiac output is increased

76
Q

Why is there more ventilation in the inferior regions of the lung?

A

Gravity compresses the lung tissue inferiorly, easier to ventilate considering the alveoli compliance has increases, greater ability to recoil and stretch for ventilation.
More recruitment of vessels, higher flow arte inferiorly causes greater perfusion

77
Q

Which part of the lung has the greatest perfusion?

A

More perfusion occurs at the base of the lung than the apex due to gravity causing greater preferential.

BRS (RF) (38 decks)

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