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Pharmacy Year 2 Semester 1 > Patient - Haemodynamics(unfinished) > Flashcards

Patient - Haemodynamics(unfinished) Flashcards

1
Q

Cardiac output depends on what 2 factors?

A

Autonomic nervous input

Venous filling pressure

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2
Q

CO=?

A

CO=Cardiac output=HRxSV
HR=heart rate
SV=stroke volume

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3
Q

What drives filling of ventricles during diastole?

A

Venous pressure

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4
Q

What does the aortic pressure resist during systole?

A

Aortic pressure resists flow out of left ventricle during systole

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5
Q

Define preload

A

The amount of stretch in the heart prior to contraction

i. e.
- Tension in expanded ventricle (due to venous filling)
- Greater stretch = myocytes need more energy (and oxygen) per contraction

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6
Q

Define afterload

A

The arterial pressure the ventricle must push against

-greater contractile force = more energy (and oxygen) use

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7
Q

What sets energy consumption?

A

Preload and afterload

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8
Q

What do both preload and afterload depend on?

A

The vascular system

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9
Q

Apart from transporting blood to all tissues, what else does the vascular system do? What is haemodynamics?

A
  • interacts with cardiac function to control blood flows and pressures throughout the body
  • This aspect - the physics of blood flow - is called haemodynamics
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10
Q

Define haemodynamics

A

The physics of blood flow

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11
Q

What is flow resistance?

A

The relationship between pressure and flow

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12
Q

How is flow resistance controlled?

A

By changing vessel diameter (by constriction and relaxation of vascular smooth muscle)

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13
Q

Define resistance in haemodynamics

A

R= Pressure/Flow

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14
Q

What can resistance be applied to?

A

An individual vessel/tube
or
An entire vascular branch e.g.
The peripheral circulation or the pulmonary circulation

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15
Q

What is Poiseuille’s Law?

A 
R= change in P/F = 128/pi x nL/D^4 
It describes flow resistance (R) of an individual vessel or tube 
where n=blood viscosity 
L=length
D=diameter
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16
Q

What is flow resistance proportional to?

What is it inversely proportional to?

A

Proportional to blood viscosity and length

Inversely proportional to diameter

17
Q

What is blood viscosity dependent on?

A

Haematocrit and protein content

18
Q

Describe how the haemodynamics of resistance differs when in networks of vessels

A
  • resistance is additive in series (sum of all section)

- resistance within a section (in parallel) is inversely proportional to the number of vessels (~1/n)

19
Q

Is resistance lower in parallel or series? (of blood vessels)

A

R is lower in parallel

20
Q

The smallest vessels have the most or greatest resistance to flow?

A

The greatest resistance to flow because pressure drops across each section from the aorta to the capillaries, but flow is the same
Lower resistance is due to the smaller diameter

21
Q

What is total peripheral resistance?

Give the PRU formula

A

Also called systemic vascular resistance
1PRU = 100mmHg/100ml/s =~ (MAP-RAP)/CO
Where PRU= peripheral resistance unit
MAP= mean arterial pressure =~100mmHg
RAP= Right atrial pressure =~ 0 (relative to atmospheric)

22
Q

What is the normal physiological range of PRU?

A

0.2-4 PRU (peripheral resistance units)

23
Q

Total pulmonary resistance=

A

Pulmonary circulation is a low resistance (low pressure) system
0.12PRU
i.e. 10% of the TPR
Mean pulmonary artery pressure minus left atrial pressure~12mmHg=12PRU

24
Q

Normal physiological range of the pulmonary resistance?

A

0.03 to 1 PRU

25
Q

Vessel structure from inside to outside

A

1 - Endothelium (all vessels)
2 - Smooth muscle (arteries-thick, veins-thinner, not in capillaries)
3 - Connective tissue (adventitia), arteries and veins, not in capillaries

26
Q

Increase in vascular smooth muscle tone causes..

A

reduction in diameter

27
Q

Reduction in diameter causes..

A

greater flow resistance (only really significant in the smallest vessels, arterioles, capillaries, venules)

28
Q

Greater flow resistance means

A

Reduced volume
increase in venous pressure and cardiac filling
Particularly important effect in large veins

29
Q

Vessel diameter affected by balance between what 2 factors?

What do these factors affect?

A

2 factors = internal pressure and tension in vessel wall

They affect the volume of blood and resistance to flow

30
Q

What is critical closing pressure

A

When arterial pressure falls to <20mmHg, tension in the artery wall collapses the vessel and shuts down flow

31
Q

What is flow autoregulation?

A

If pressure surges, stretch-gated receptors in smooth muscle react to increase tone (acting to increase flow resistance and minimise changes in flow)

32
Q

If pressure gets to low, what happens?

A

Reach critical closing pressure

Vessel will collapse

Pharmacy Year 2 Semester 1 (32 decks)

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