Chapter 23-Venous hemodynamics Flashcards
What is the primary function of the venous system?
Return blood to the heart ; serves as a reservoir for blood
What are The four main components for effective venous return to the heart?
1 – central pump
2- pressure gradient
3- peripheral venous pump
4- Competent venous valves
What are the two main types of pressure in the venous system?
Dynamic pressure and hydrostatic pressure
What is hydrostatic pressure?
The weight of the column of blood from the heart to any given spot in the body
What drives blood through the Venous system?
The contraction of the heart
What type of vessel has the Biggest pressure drop?
On Test
Arterioles
Resistive vessels!
What a patient is supine, there is little to no hydrostatic pressure,
True or false
True
When you are sleeping supine on your back, what is the hydrostatic pressure in the right atrium?
0 mm/hg
When you are sleeping supine on your back , what is the hydrostatic pressure in the leg?
8 mmhg
The hydrostatic pressure at the ankle of a normal height person standing is approximately _______ mm/hg
100
If a patient is standing up and has their right arm above their head what is the hydrostatic pressure above the right atrium
-50 mm/hg
Veins collapsed at what hydrostatic pressure?
0 mm/hg
What is the Valsalva maneuver And what is it used for?
To check for insufficient valves
Patient takes a deep breath in and bears down. This increases intrathoracic and intraabdominal pressure dropping ALL venous flow
Inspiration ____ the diaphragm and expiration ______ the diaphragm
lowers/Raises
Inspiration lowers the diaphragm which decreases the infra-thoracic pressure and increase abdominal pressure
Expiration raises the diaphragm, increases intra-thoracic pressure and decrease intra-abdominal pressure
When you breath in, this _____ the venous return to lower extremity but ___ return to upper
Decrease / increase
When you breath in, this DECREASES the venous return to lower extremity but INCREASE return to upper
Decrease / increase
When you breath out (expiration), this _____ the venous return to lower extremity but ___ return to upper
Decrease / increase
When you breath out (expiration), this INCREASES the venous return to lower extremity but DECREASES return to upper
Decrease / increase
What is the most important Peripheral pump in the body
A calf muscle pump
Helps propel blood upward
When is the calf muscle pump activated?
With walking
Explain the process of the calf muscle contraction…
1- The muscles contract which squeezes deep veins
2-blood flows to heart in both superficial and deep system
3- valves prevent backwards flow
4-perforator valves are closed
Explain the calf muscle pump process…
1- Deep veins decompress and expand back
2- blood is drawn from superficial to deep veins through the perforators
3-blood is sucked from capillaries and veins through the calf
4- upstream valves are closed, reducing local venous pressure.
Explain the process of an ineffective calf muscle pump
1- blood flows from deep to superficial veins thru the incompetent perforators
2- blood flows distally to foot
3-Inefficient circular flow of blood
4- venous pooling and venous hypertension when walking.
Venous valves are one way valves that direct flow inward and downward.
True or false
FALSE
Valves direct flow inward and upward
An ineffective muscle pump results in the inability for the pump to do what it’s supposed to. This results in?
poor muscle contraction
The purpose of the muscle pump is to propel the blood flow up and to closer to the heart. It can’t do that if it can’t contract
Cardiac output equals venous return
True or false
True
Ambulatory venous hypertension can be caused by??
ineffective calf muscle
Veins are very COMPLIANT vessels, able to accomodate large changes in volume within a small change of pressure or time
TRUE
A distended vein has ____ transmural pressure whereas a flattened vein has ___ transmural pressure
Distended vein has high pressure
Flattened vein has lower transmural pressure
A distended vein will offer___ resistance than a flattened vein
Lower-higher?
Lower resitance
When the heart contracts, this creates _____ pressure
dynamic pressure
What is the formula for calculating hydrostatic pressure?
P x G x H = hydostatic pressure
P = gravity of blood
G- acceleration of gravity
h- distance from heart/height
Without activation of the muscle pumps, dynamic pressure is inadequate to return blood from the limb to the heart. What will result from this?
venous hypertension
What are a few reasons why someone would have an ineffective muscle pump
Patient doesnt walk, fused ankle, hemiparesis.
Having an ineffective muscle pump decreases ejection of blood, which allows reflux to occur.
What is transmural pressure?
the pressure difference between the outside of the vessel (tissue pressure versus within the vessel.
