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Year 3 Cardiac physiology > CC9: Cardiac output 2 > Flashcards

CC9: Cardiac output 2 Flashcards

1
Q

What is a normal stroke volume?

A

60-100ml/beat
SV index = 33-47ml/beat/m^2

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2
Q

What is a normal cardiac output?

A

4-8L/min
Cardiac index = 2-4L/min/m^2

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3
Q

What is the Fick principle?

A

-As blood goes through organs, there is a reduction in O2 and increase in CO2
-As blood goes through lungs, there is an increase in O2 and a decrease in CO2

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4
Q

What is cardiac index?

A

Cardiac output/Body surface area

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5
Q

What is the Fick formula?

A
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6
Q

What is the VO2 max of the average, untrained, healthy male and female?

A

Male = 35-40mL/kg/min
Female = 27-31mL/kg/min

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7
Q

How do calculate BSA?

A
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8
Q

How do calculate VO2?

A

VO2 = 125 x BSA

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9
Q

What are the ways of measuring VO2

A

Direct:
-Measure using respiratory techniques

Indirect:
-Predict from regression equations
-Derive from normal tables

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10
Q

Fick principle in systemic circulation

A
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11
Q

Fick principle in pulmonary circulation

A
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12
Q

What are the direct respiratory techniques for measuring VO2?

A

Spirometry
-Expired gas returned via soda lime filter
-Reduction in gas volume due to consumption of oxygen

Metabolic cart
-Inspired O2 volume/concentration and expired O2 volume/concentration measured by:
-Mass spectrometer
-Paramagnetic analyser

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13
Q

Fick formula in body

A
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14
Q

Fick formula in lungs

A
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15
Q

What is oxygen content (CaO2)?

A

CaO2 = the total amount of O2 in the blood, both attached to Hb and dissolved in the plasma

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16
Q

What is Hufner’s factor?

A

-Combining power of Hb
-1 gram of Hb can combine maximally with 1.34ml O2

17
Q

How much O2 is dissolved in the plasma?

A

-Small amount of O2 is dissolved into plasma
-This increases when inspired air contains more oxygen than normal room air
-At PO2 = 100mmHg,
dissolved O2 = 0.3ml/100ml plasma
-Generally, dissolved O2 is not significant

18
Q

What is oxygen capacity?

A

-Maximum amount of oxygen able to be carried by haemoglobin (ml/g)

19
Q

How to calculate Oxygen capacity and content?

A

O2 capacity = Hb x 1.34
O2 content = O2 capacity x saturation

20
Q

Calculate CaO2 and CvO2

A

CaO2 = 13 x 1.34 x 0.98
CvO2 = 13 x 1.34 x 0.61

21
Q

What does low A-V O2 difference indicate?

A

-High CO - well oxygenated blood moves rapidly through the capillary
-Septic shock - cells extract less O2

22
Q

What does high A-V O2 difference indicate?

A

-Low CO - slow blood flow
-Increased VO2 - tissues extracting more O2

23
Q

What is the effective pulmonary blood flow?

A

-The amount of deoxygenated blood pumped to the lungs that the lungs can ‘effectively’ oxygenate

24
Q

What is an example of ‘ineffective’ pulmonary flow?

A

-Child with left to right shunting through PDA
-Extra blood pumped to lungs is already fully oxygenated
-The lungs cannot further oxygenate this ‘red’ blood

25
Q

What is vascular resistance?

A

-The resistance that must be overcome to push blood through the circulatory system and create flow

26
Q

What is the SVR?

A

Systemic vascular resistance
-The resistance offered by the peripheral circulation
-Also called Total Peripheral Resistance (TPR)

27
Q

What is the PVR?

A

Pulmonary vascular resistance
-The resistance offered by the vasculature of the lungs

28
Q

What is the formula for resistance?

29
Q

Vascular system parameters

30
Q

Formula for SVR

A

SVR = Systemic vascular resistance
Ao = Mean aortic pressure
RA = Mean right atrial pressure
SBF = Systemic blood flow (Qs)

31
Q

Formula for PVR

A

PVR = Pulmonary vascular resistance
PA = Mean pulmonary artery pressure
LA = Mean left atrial pressure
PBF = Pulmonary blood flow (Qp)

32
Q

What is normal SVR and SVRi?

A

SVR = 10.0-16.3 HRU
SVRi = 24.6-30 HRU

33
Q

What is normal PVR and PVRi?

A

PVR = 1.9-3.2 HRU
PVRi = 3.2-3.6 HRU

34
Q

What increases/decreases SVR?

A

Increased by:
-aortic valve stenosis
-elevated BP
-polycythemia

Decreased by:
-use of vasodilators

35
Q

How do you normalise vascular resistance for body surface area?

A

SVRI = SVR x BSA
-Multiply vascular vascular resistance by body surface area

36
Q

What do you do to HRU value to get Absolute Resistance Units (ARU) dynes/sec/cm^-5

A

HRU x 80 = ARU

37
Q

Relationship between PVR and PHT

A

-PHT is often the result of increased PVR
-To test for reversible increase in PVR breathe 100% O2
-In reversible disease this will cause dilation of pulmonary vasculature

38
Q

What are the guidelines for vascular resistance ratio?

A

Vascular resistance ratio = PVR/SVR
<0.25 normal
0.25-0.75 mild pulmonary vascular disease
0.45-0.75 moderate pulmonary vascular disease
>0.75 severe pulmonary vascular disease
>1.0 corrective surgery unsuccessful (transplant instead)

Year 3 Cardiac physiology (30 decks)

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