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DMST 265 VASC 1 > Module 2 Venous hemodynamics > Flashcards

Module 2 Venous hemodynamics Flashcards

1
Q

What is the primary function of the veins?

A

Return nutrient deficient blood back to heart

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2
Q

Veins act a reservior to do what?

A

Maintain homeostasis with 65% blood volume moving through veins at one time

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3
Q

Vein walls can expand and contract depending on what? 3

A
  1. Pressures
  2. Volumes
  3. Flow
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4
Q

The different pressures that effect the vein shape are what? 2

A
  1. Intramural (internal)
  2. Interstitial (external)
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5
Q

What does the veins permit in terms of blood pressure and volume?

A

Increase of blood volume without a significant increase in venous pressure

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6
Q

Veins are less elastic than arteries but more what?

A

Compliant

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7
Q

Veins adapt to changes in blood volume as a result of what? 4

A
  1. Limb position
  2. Muscle pump activity
  3. Venous valve functions
  4. Blood volume
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8
Q

Surplus fluids can be stored or adjusted to what?

A

Blood loss

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9
Q

Veins act similarly to what?

A

Rubber bands and can be stretched and collapsed in a variety of sizes

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10
Q

Extreme fluid overload or severe blood loss will affect what?

A

Central venous pressure

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11
Q

Veins have little resistance to blood flow when in what position?

A

In a supine position

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12
Q

The pressure difference form post capillary vein and the heart is what?

A

Low

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13
Q

Venous flow is affected by what?

A

Posture changes

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14
Q

Venous return to the heart is assisted by what? 4

A
  1. Cardiac cycle
  2. Respiration
  3. Muscles
  4. Valves
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15
Q

Muscular contraction of the heart affects what?

A

Pressure and flow of venous blood

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16
Q

Cardiac activity is evident where? 2

A
  1. Large central veins
  2. Large head and neck veins
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17
Q

Two periods of heart cycle increase venous flow, what are they?

A
  1. Opening of tricuspid valve
  2. Ventricular systole
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18
Q

When the tricuspid valve opens there is more what?

A

Volume in the heart, dropping the pressure

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19
Q

When the right ventricle contracts, what does it do? ( TV, RA, volume)

A
  1. Pulls the tricuspid valve down
  2. Expanding the right atrium
  3. Increasing the volume
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20
Q

What is respirophasicity?

A

Venous flow affected by movement of diaphragm

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21
Q

What are the two phases of breathing?

A

Inspiration and expiration

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22
Q

Effects of breathing vary with what?

A

Position and area of the body

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23
Q

Valsalva maneuver does what?

A

Increases pressure above and below diaphragm

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24
Q

During inspiration what is the diaphragm motion like?

A

Moves inferior

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25
During expiration what is the diaphragm motion?
Superior
26
What is the intra-abdominal pressures during inspiration?
Increase
27
What is the intra-abdominal pressures during expiration?
Decrease
28
What is the intra-thoracic pressure during inspiration?
Decrease
29
What is the intra-thoracic pressures during expiration?
Increase
30
During inspiration what happens to the IVC?
Collapses
31
During expiration what happens to the IVC?
Dilates
32
During inspiration what happens to the lower extremity venous return?
Decrease
33
During expiration what happens to lower extremity venous return?
Increase
34
During inspiration what happens to the upper extremity venous return?
Increase
35
During Expiration what happens during upper extremity venous return?
Decrease
36
Respiration effects can be diminished in what? 2
1. Supine position 2. Shallow breather
37
Upper extremities can be more pulsatile because of what?
Close proximity to the heart
38
Respiration has less of an effect on venous flow when in what position?
Venous flow when standing
39
Contraction of voluntary muscles do what for veins?
Propels blood towards the heart
40
In the presence of normal functional valves the blood will flow how?
In one direction
41
Contraction results in decreased what? (Pressure wise)
Venous pressure by interrupting the hydrostatic column of blood
42
At rest, with no muscle activity what does the veins do?
Act as reservoirs for blood collection
43
Muscle contractions results in what in the veins? 3
1. Decreased venous pooling 2. Decreased capillary pressure 3. Increased blood flow
44
What does a muscle contraction do in terms of venous flow?
Assists in venous flow in the deep and superficial veins is towards the heart
45
What is muscle relaxation in relation to the venous system?
Small amount of flow occurs in the perforators, from the superficial to the deep veins
46
What is the calf pump?
Contraction of the gastronemius and soleus muscles to most efficiently move blood.
47
What is the calf capacitance high? (How much force is generated per pump)
Generates pressures of about 200 mmHg per contraction
48
What happens in a single contraction of a calf pump?
40-60% of the venous volume is ejected
49
What does calf pump do? 2
Acts as a venous "heart" and 1. Squeeze the calf veins 2. Propels blood towards the heart.
50
The efficiency of the calf pump is dependent on what? 3
1. Ability of the calf muscles to contract 2. Competency of the venous valves 3. Patency of the outflow veins
51
What does the venous valves do?
Direct blood flow to the heart and prevent retrograde flow (reflux)
52
What kind of valves are available in venous valves?
Bicuspid and arise from the intimal layer
53
Valves in perferator veins do what?
Direct flow from the superficial to deep veins
54
At the valve site what happens to the vein?
Veins dilate slightly at the sinus and expands with increased pressure
55
Where is a frequent site of thrombi formation due to stagnant flow?
Venous valves
56
What impedes Venous return? 2
1. Gravity 2. Hydrostatic pressure
57
For every 12 inches of vertical distance what happens?
22 mmHg of pressure is added
58
What is hydrostatic pressure?
The weight of a column of blood at a given point
59
Hydrostatic pressure is relative to what?
Right atrial pressure of zero
60
What is hydrostatic pressure above the heart?
negative pressure
61
When supine hydrostatic pressure is what?
Negligible (about 15 mmHg)
62
When standing the ankle pressure rises to around what?
110 mmHg and the legs veins dilate to accept the blood pooling
63
ASVD refers to what?
Blood volume
64
When we walk what is the hydrostatic pressures?
25 mmHG
65
What does transmural pressure determine?
The cross sectional shape of the vein
66
What is transmural pressure?
The difference between intraluminal and interstitial pressure
67
Intraluminal pressure is what?
The pressure within the vein walls
68
Interstitial pressure is what?
The pressure exerted from outside the vein by surrounding tissue and fluid
69
What is low transmural pressure?
The vein wall collapses and becomes elliptical in shape
70
What is high transmural pressure?
The vein wall becomes circular and may even distend at higher venous pressures
71
What makes intraluminal pressure?
Hydrostatic pressure
72
Aside from the images of the vessels, we can identify normal and abnormal venous returns by evaluating what?
Doppler waveforms
73
What is respirophasic?
When antegrade flow between the upper and lower extremity wave form is opposite due to changes in intrathoracic and intra-abdominal pressure. **The appearances between upper and lower extremities can be the same but the difference is with inspiration/ expiration.**
74
When a valsalva maneuver is performed what happens to intra-abdominal and intrathoracic pressure? What results from this?
Increased thoracic and abdominal pressure which in turn increases the pressure in both the upper and lower extremity veins
75
During valsalva maneuver flow should do what?
It should stop or diminish in upper and lower extremities
76
During valsalva maneuver release of breath will do what to flow?
Increase or augment flow
77
It is normal when we see flow during valvsalva?
Abnormal response is a reverse of flow
78
Some abnormal venous waveforms we will encounter are what? 3
1. Continuously 2. Pulsation 3. Reflux
79
What is the abnormal waveform of continuous?
A lack of respirophasicity usually the result of a more proximal obstruction from a clot or extrinsic mass
80
What is the abnormal waveform of pulsatile?
When the heart beat is reflected into vessels further from the heart because of increased central venous pressure related to heart conditions
81
What is the abnormal wave form of reflux?
Retrograde flow as a result of valve incompetence or Venus distension. A small amount is normal, but if prolonged represents venous insufficiency.

DMST 265 VASC 1 (19 decks)

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