Vascular

Question 1

Central Venous Pressure (CVP) “Right Atrial Pressure”
Value /represents what and its significance

Answer 1

Value= 0-2 mm Hg
Represents balance between VR & pumping ability of the heart Significance:
1- Main force for ventricular filling.
2- Difference between CVP and mean systemic filling pressure is the gradient for VR
3- Index of blood volume
4- CVP: ↓ in hemorrhage
5- CVP: ↑ in right-sided heart failure

Question 2

Peripheral venous pressure 3 values

Answer 2

✓ In peripheral small venules= 12 mmHg
✓ In large veins outside thorax = 6 mmHg
✓ In large veins entering right atrium= 4 > CVP

Question 3

VP determined by

Answer 3

• blood volume
• venous capacity (Compliance)

Question 4

Factors affecting Venous pressure (Pv)

Answer 4

1- CO:
• ↓CO (heart failure) →↑ venous blood volume → ↑venous pressure
2- Blood volume:
• ↑blood volume (renal failure) →↑ venous pressure Vice versa in hemorrhage
3- Arteriolar dilation → ↑ venous pressure
4- Venous capacity (tone):
• ↑venous tone (Sympathetic stimulation) →↓capacity →↑ pressure 5- Effect of Gravity on Venous Pressure: In upright position
Each cm below level of right atrium . Each cm above level of right atrium (in head veins)
↑ Pressure by 0.77 mm Hg ↓Pressure by 0.77 mm Hg →
↑pressure in leg veins from 12 in recumbency Neck veins are collapsed as pressure inside them is sub-atm
to 80 mmHg during standing → edema & varicose veins

Question 5

Mechanical factors help VR against gravity

Answer 5

1. Muscle Pump compresses the veins.
2. Valves → Prevent retrograde flow (incompetent valves →Varicose veins)
   Diaphragmatic descent →↓intrapleural pressure →↓ pressure in thoracic veins &↑pressure in abdominal veins →↑ VR.
3. Heartbeat Effects

Ventricular suction. Atrial suction
During rapid filling phase. During rapid ejection phase
Opening of tricuspid valve → low ventricular. Downward pulling of atrioventricular cusps
pressure suck blood from atria & veins. → ↓atrial pressure → suction of the blood.

Question 6

Venous Return Curve

Answer 6

• Relation between RAP and VR
• Venous return: volume of blood flows back to the heart / minute.
• Determined by Ohm’s law 1. Effect of RAP on VR curve
VR = CO (5 l/min)
↑RAP →↓ VR

Question 7

Effect of RAP on VR curve

Answer 7

↑RAP →↓ VR. ↓RAP →↑ VR
When RAP = 7 mmHg= MSFP VR = zero. ↓ RAP ≤ -1 mmHg→ VR reach plateau
negative pressure causes collapse of thoracic veins

Question 8

Effect of MSFP on VR curve:

Answer 8

MSFP: is the pressure all over systemic circulation if heart stops pumping • When CO = zero → MABP = RAP= 6-8 mmHg
• Reflects degree of distension of circulation with blood
• Relation between Blood volume & Capacity of the circulation (mainly capacity of veins)

↑blood volume (in renal failure) ↓capacity (↑sympathetic)—-↑MSFP
Shift the curve up & right→↑VR

↓ blood volume (hemorrhage) ↑capacity (↓sympathetic)——↓MSFP
Shift the curve down & left →↓VR

Question 9

Effect of RVR on VR curve

Answer 9

↓RVR →↑ slope of VR curve → ↑VR (vice versa)
• Changes in RVR not affect the value of MSFP