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Cardio respiratory mechanics Flashcards

(50 cards)

1
Q

Draw the graph for how the volume of air in the lungs change during inspiration and expiration

A
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2
Q

draw the graph for Palv and flow rate during inspiration and expiration

why do they look so similar

A

They look similar because air flows down pressure gradient. The greater the presure the greater the flow rate

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3
Q

draw the graph to show how the pressure in the pleura changes during inspiration and expiration.

Try to explain the significance

A
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4
Q

draw a flow volume loop and explain what each point and loop signify

A
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5
Q

what is the protocol in order to perform a pulmonary function test

A
  • patient wears noseclip
  • Patient wraps lips round mouthpiece
  • Patient completes atleast one tidal breath
  • Patient inhales steadily to total lung capacity
  • Patient exhales as hard and fast as possible
  • exhalation continues until Residual voulme is reached
  • patient immediately inhales to total lung capacity
  • visually inspect performacne and volume time curve and repeat if neccessary
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6
Q

after performing the pulmonary function test, what should you look out for?

A
  • Inconsistencies with clinical picture
  • Interrupted flow data
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7
Q

draw the flow volume curve for mild obstructive lung diseases

A
  • displaced to the left
  • indented exhalation curve
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8
Q

draw the flow volume loop for severe obstructive disease

A
  • Shorter curve
  • displaced to the left
  • indented exhalation curve
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9
Q

draw the flow-volume loop for restrictive lung disease

A
  • displaced to the right
  • narrower curve
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10
Q

draw the flow volume loop for variable EXTRATHORACIC obstruction

A
  • Blunted inspiratory curve
  • Otherwise normal
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11
Q

draw the flow volume loop for INTRATHORACIC obstruction

A
  • Blunted expiratory curve
  • otherwise normal
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12
Q

draw the flow volume loop for FIXED AIRWAY obstruction

A
  • Blunted inspiratory and expiratory curve
  • otherwise normal
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13
Q

How is resistance to flow related to diameter

A

Inversely proportional to 4th power of radius

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14
Q

Why doesn’t the resistance continue to increase as airways get smaller

A

They branch out more and the increased surface area reduce the overall resistance of the system

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15
Q

How does resistance and conductance of airway change with increasing lung volume.

give reasons why

A
  • Resistance decreases (1/x equation)
  • conductance increases at a constant rate- airway dilates as lung volume increases
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16
Q

What is Poiseuille’s Law

A
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17
Q

What is the purpose of te extensive smooth muscles in arteries and arterioles

A

They help to regulate diameter and resistance to blood flow

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18
Q

What is the purpose of the highly compliant venules and veins?

A

Act as reservoir for blood volume; can easily expand and stretch to have mor blood.

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19
Q

Draw the graph for how total surface of vessels, Mean pressure and proportion of systemic blood volume varies across, arteries, veins and capillaries

A
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20
Q

Why does pressure fall across circulation? And what vessels present more resistance to flow?

A

Pressure falls due to viscous (frictional) pressure losses and the small arteries and arterioles present most resistance to flow

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21
Q

What is the relation between Mean arterial pressure and cardiac output ?

A

P= Qx TPR (Total peripheral resistance)

Q- cardiac output

22
Q

What are the assumptions taken in order to derive the equation that relates mean arterial pressure and cardiac output?

A
  • There’s steady flow
  • the vessels are rigid
  • right atrial pressure is negligible
23
Q

Physiologically, how is regulation of flow of blood achieved

A

This is achieved by variation in resistance of the vessels, whilst blood pressure remain as relatively constant

24
Q

What does resistance of a tube to flow depends on?

A

Poiseuille’s law

  • fluid viscosity
  • length of tube
  • inner radius of tube

hence small changes in vascular tone can produce large changes to flow

25
Draw out the distribution of blood to organs at rest **and** at ***exercise.*** ## Footnote ***what Are the respective cardiac outputs?***
Rest- cardiac output is 5L/min exrecise- cardiac output is 20L/min
26
What are the 2 different types of flow of blood in vessels
Laminar and turbulent
27
What are the characteristics of **Laminar** flow?
* Velocity of fluid is constant at any one point AND flows in layers * Blood flows fastest when closest to the centre of the lumen. Peak velocity is in the middle in a straight line
28
What are the characteristics of **Turbulent** Flow?
* Blood flows erratically, forming eddys * blood is prone to pooling * associated with pathophysiological changes to the endothelial lining of the blood vessels.
29
How can pulse pressure be calculated?
Systolic blood pressure ***minus*** Diastolic blood pressure
30
What causes this dichroic notch seen in the diagram
Closure of the aortic valve
31
How can mean arterial pressure be calculated WITHOUT cardiac output
MAP= DBP + 1/3 Pulse pressure
32
How does slow deflation of cuff of blood pressure measurement allow us to auscultate blood
Causes turbulent flow
33
What is compliance
***Tendency to distort under pressure*** - caused by the relationship between transmural pressure and vessel volume change in volume/ change in pressure
34
What is elastance?
Tendency to recoil to it's original volume change in pressure/ change in volume
35
How does ventricular pressure and aortic pressure changes after ejection? Explain why?
Once aortic valve closes, ventricular pressure falls rapidly to zero but aortic pressure falls more slowly. this is due to large arteries and aorta elasticity which act to buffers the change in pressure elasticity is related to compliance
36
How does MAP increases with age due to changes in arterial compliance
Age makes artery stiffer and compliance decreases. Hence windkessel effect is reduced and DBP is higher this increases pulse pressure
37
Explain arterial compliance
38
What are the 2 methods of facilitated venous return?
1. S**keletal pump**: muscle contracts to squeeze veins one way up towards IVC 2. ***Respiratory pump***- inspiration decreases pressure in thoracic cavity and opens up IVC. Steeper pressure gradient for venous return.
39
What causes Varicosity?
Incompetent valves in veins causes dilated superficial veins in legs. There's more back flow of blood.
40
What causes oedema in feet?
Prolonged elevation of venous pressure even with intact compensatory mechanisms
41
Explain the mechanism with why aneurysm can form and how it can lead to haemorrhage
* Vascular aneurysm increases radius of vessel * for the same internal outward pressure, the muscle wall must produce a inward tension (this increases now due to increased radius) * if muscle fibres cant meet demands due to it's weakened , aneurysm continues to expands until it may ruptures. LAW OF LAPLACE
42
What is an aneurysm and what does aneurysmal dilation of the abdominal gut lead to?
Aneurysm- balloon-like distension formed due to vessel wall weakening Aneurysmal dilation of abdominal aorta can lead to the formation of **diverticuliti** in the gut
43
What can severe transmural pressure cause? But why doesn't it happen to large airways?
Can collapse small- to medium airways but doesn't collapse large airways as the supported with cartilage
44
What is the difference in ventilation and perfusion between base and apex of lung?
Base of lung has higher ventilation and perfusion
45
Why is perfusion Greater at base of lung than at apex
At base theres higher intravascular pressure due to gravity effect hence this leads to: * More recruitment * less resistance * Higher flow rate
46
Why is ventilation greater at the base of the lung than at apex?
At apex pleural pressure is MORE NEGATIVE (-8cmH2O). Less compliant, larger alveoli hence less ventilation At base: theres **smaller transmural pressure gradient** (pleural pressure is less negative) also there's **small alveoli and they are more compliant**; this leads to **more** ventilation
47
How does the ventilation, perfusion and Ventilation/Perfusion ratio change from **base to apex** of lung? draw the graph explain any differences seen
Ventilation and perfusion both decrease Perfusion decrease at a faster rate as blood is more dense than air the ventilation/perfusion ratio increases
48
Compare the different pressures in the zones of the lungs from **apex to base** where apex is zone 1 and base is zone 3. Write in descending order PA = Alveolar pressure Pa = arterial pressure Pv = venous pressure
Zone 1 = PA\>Pa\>Pv Zone 2 = Pa\>PA\>Pv Zone 3 = Pa\>Pv\>PA
49
Compare the compliance of artery and vein at **low pressure**
Venous compliance is 10 to 20 times greater than arterial complicates at low pressure
50
What is the effect of increasing smooth muscle contraction on **venous** compliance
This decreases ***venous*** volume and increases venous pressure since most blood is stored in the veins, any small dilation in veins can increase volume of blood stored in them.