Cardiac Output Flashcards
1
Q
Definitions of cardiac output
A
- The volume of blood pumped by each ventricle into the aorta per minute.
- The volume of blood flowing through either the systemic or the pulmonary circuit per minute.
2
Q
Formula for cardiac output
A
Heart rates x stroke volume
3
Q
What is the stroke volume?
A
The blood volume ejected by each ventricle with each beat:
4
Q
What is the unit of cardiac output?
A
Liters per minute
5
Q
What is the value of cardiac output in men and women?
A
Men - 5.6
Women - 4.9
6
Q
CO is greater in children. True or false?
A
False
7
Q
CO is less in females. True or false?
A
True
8
Q
The bigger you are, the less your CO. True or false?
A
False
9
Q
Which time of the day is CO low?
A
In the morning
10
Q
Environmental temperature and CO
A
Increase >30⁰C affects CO
11
Q
Effect of anxiety on CO
A
It increases CO
12
Q
After eating, CO…
A
Increases
13
Q
CO and exercise
A
Directly proportional
14
Q
Effect of high altitude on CO
A
It increases as a result of hypoxia
15
Q
When is CO higher - recumbent or upright?
A
Recumbent
16
Q
CO and pregnancy
A
It increases in the last trimester
17
Q
CO and sleep
A
It decreases when one is sleeping
18
Q
Effect of fever on CO
A
Decreases CO
19
Q
Anemia
A
Decreases CO
20
Q
Hyperthyroidism
A
Increases CO
21
Q
Hypothyroidism
A
Reduces CO
22
Q
What is atrial fibrillation?
A
When there is an irregular, often rapid heart rate that commonly causes poor blood flow. It happens because the heart’s upper chambers beat out of coordination with the lower chambers
23
Q
Effects of atrial fibrillation on CO
A
Decreases CO
24
Q
Heart failure
A
Decreases CO
25
Shock
Decreases CO
26
Hemmorhage
Decreases CO
27
The factors responsible for the regulation of CO can be divided into...
Two - Cardiac and peripheral factors
28
What are the cardiac factors that affect the regulation of cardiac output?
Force of contraction of the heart
| Heart rate
29
What are the peripheral factors that affect the regulation of cardiac output?
Venous return
| Peripheral resistance
30
States the Starling law
It states that the force of contraction of the heart is directly proportional to the initial length of muscle fibers before the onset of contraction.
31
What is the preload?
It is the stretching of the cardiac muscle fibers at the end of diastole just before contraction.
32
What is the EDV?
The end diastolic volume is the total volume of blood at the end of diastole (relaxation)
33
The pre-load is also the tension on the wall of the ventricle due to the end diastolic volume. True or false?
True
34
The force of contraction of the heart depends on two factors. What are they?
Pre-load
After load
Length of muscle fibers before contraction
35
What is the afterload?
It is the force against which the ventricles most contract and eject blood
36
What determines the after load for the left ventricle?
The aortic pressure which opposes the ventricle as it tries to pump blood into the aorta
37
Afterload is inversely proportional to the ventricular force and CO. True or false?
True
38
Relationship between ventricular force and aortic pressure for blood pumping
The ventricular force must be more than the aortic pressure for blood to be pumped into the systemic circulation
39
The higher the preload...
The higher the fibres length, force, volume and CO
40
The higher the after load...
The less the CO
41
Factors that can cause hypereffectivity of the heart
Nervous stimulation
| Hypertrophy of the heart muscle
42
Factors that can cause hypoeffectivity of the heart
- Inhibition of nervous excitation of the heart
| - Pathological factors: arrhythmia, valvular heart diseases, hypertension
43
What is hypertrophy?
Enlargement of an organ
44
The higher the heart rate...
...the higher the cardiac output
45
Effects of SNS & PNS on CO
SNS - Increased
| PNS - Reduced
46
Who maintains the arterial blood pressure when the venous return and cardiac output increase?
The heart rate
47
What is chronotropy?
The hearts rate
48
What is ionotropy?
Contraction
49
What is dromotropy?
Conduction velocity
50
What is venous return?
It is the rate of blood flow back to the hearts
51
Venous return normally limits CO, true or false?
True
52
The higher the volume of blood that the heart receives, the less the cardiac output. True or false?
False, the greater it is
53
Factors that affect VR
```
Respiratory pump
Muscle pump
Gravity
Venous pressure
Sympathetic tone
Vis-a-tergo
Vis-a-fronte
```
54
Relationship between inspiration and expiration and cardiac output.
During inspiration, there is a reduction in the resistance to the flow of blood into the hearts and as such there’s increased venous return and increased cardiac output
55
Relationship between venous return and cardiac output
The higher the VR the higher the CO
56
During skeletal muscle contraction, proximal valves close while distal valves open. True or false?
False. The inverse is the case
57
The higher the muscle contraction and relaxation, the higher the venous return and cardiac output. True or false?
True
58
Effects of gravity on venous return
It causes venous pulling and reduction in VR
59
Venous gradients from the veins to the right atrium does not affect VR, true or false?
False, it does
60
Vis-a-tergo
Residual force of propulsion from the left ventricle
61
Vis-a-fronte
Force of thoracic aspiration during inspiration
62
Does venooconstriction aid VR?
Yes
63
Where is peripheral resistance offered in the body’s circulatory system?
The arterioles
64
What is peripheral resistance?
The load against which the heart has to pump blood
65
How does peripheral resistance affect cardiac output?
It is an inverse relationship to maintain the ABP. Increase in PR only alters the CO to maintain ABP
66
Conditions in which CO is pathologically high
* Beriberi
* Arteriovenous fistula (shunt).
* Hyperthyroidism
* Anemia
67
Cardiac conditions in which CO is pathologically low
* Severe coronary blood vessel blockage and consequent myocardial infarction
* Severe valvular heart disease,
* Myocarditis - Inflammation of cardiac muscle
* Cardiac tamponade - Compression of heart because of fluid in pericardial sac
* Cardiac metabolic derangements.
68
Peripheral conditions in which CO is pathologically low
* Decreased blood volume
* Acute venous dilation
* Obstruction of the large veins
* Decreased tissue mass, especially decreased skeletal muscle mass
69
The kinds of conditions that can cause cardiac output to be pathologically low are divided into:
Cardiac and peripheral
70
Epinephrine increases heart rate. True or false?
True
71
The methods of measuring cardiac output may be...
...direct or indirect
72
Direct methods of measuring cardiac output
Use of cardiometer and flowmeter
73
Indirect methods of measuring cardiac output
- Using Ficks principle
| - Indicator dilution method
74
How to measure cardiac output
BRODDIT
```
Ballistocardiographic method
Radionuclide ventriculography
Oesophageal Doppler transducer technique
Doppler echocardiography
Direct Methods
Indirect Methods
Thermodilution technique
```
