Week 3 - Lesson 1 (Part 10) Flashcards
What do peripheral muscles (eg. calfs) act as?
An alternative pump to the heart
What does the cardiac pump do?
It brings flow back to the right atrium due to the contraction and relaxation phases of the cardiac cycle
What do venous valves establish?
Unidirectional flow
Where are valves more abundant?
In the lower legs
- decreases as it goes closer to the heart
What does respiration have a profound effect on? (2)
- Venous pressure
2. Blood flow
What happens to the thoracic pressure during inspiration?
It decreases
What happens to the abdominal pressure during inspiration?
It increases
What happens to the thoracic pressure during expiration?
It increases
What happens to the abdominal pressure during expiration?
It decreases
What is the result of increased abdominal pressure?
Pressure decreases the pressure gradients between the peripheral veins in the lower extremities
- reducing blood flow to the peripheries
What is the result of decreases abdominal pressure?
Pressure gradient from the lower limbs to the abdomen is increased
What are changes in blood flow with respiration are opposite with?
The lower limbs
What is the respiratory changes of blood flow in the upper limbs is influenced by?
Changes in posture
What happens to the upper parts of the body during respiratory?
Venous flow tends to stop at the height of inspiration and resumes with expiration
Why does venous flow tend to stop at the height of inspiration and resumes with expiration?
Probably due to compression of the subclavian vein at the level of the first rib during contraction of the accessory muscles of respiration
What does the change of thoracic and abdominal pressures do during respiration?
It opens and closes the valves while moving the blood up toward the heart and drawing blood into the right atrium
Phasicity
Changes with respiration
- want to have smooth continual changes
What can affect the flow?
Valsalva manouever
Valsalva manouever
Is performed by moderately forceful attempted exhalation against a closed airway, usually done by closing one’s mouth, pinching one’s nose shut while expelling air out as if blowing up a balloon
Where is flow most spontaneous?
When it is closest to the heart
- instant flow pattern obtainable (readily available)
When is spontaneous flow not as common?
Further from the heart
- distal femoral vein and below (less pulsatile)
Augmentation
Squeezing of the muscle
- wrap around (aliasing)
Why is augmentation used?
In venous flow can be augmented to observe a large bolus of blood flowing through a vein in an unobstructed vessel
Why are veins compressible?
Due to a thinner muscular wall
- can rule out clot this way
Venous flow characteristics (4)
- Phasicity
- Spontanaity
- Augmentation
- Compressibility
What does valsalca menoever do?
It increases intrathoracic and abdominal pressures and decreases, abolishes or even reverses flow in some peripheral veins
How does shallow breathing affect phasicity?
May not sufficiently descend the diaphragm to elevate intraabdominal pressure
- venous flow will be more continuous
Where do you see augmentation?
In a vein
- not an artery
What does augmentation tell you?
If the vein is obstructed or not
How does augmentation show if something is blocked?
You will not get a signal of a sharp increase on spectral doppler and have no warp around
- partially blocked will have a slower increases
What does valsalva manoever prove?
If the valve is competent
- properly close valves
- show up as no signal on spectral doppler
Arterial hemodynamic characteristics (5)
- Waveform reflects the cardiac cycle
- Not affected by respirations
- High pressure system
- Pulsatility
- varies according to the vascular bed it supplies - Has a pulse
Venous hemodynamic characteristics (5)
- Waveform reflects the respiratory movements
- Phasicity
- Low pressure system
- Pulsatility
- varies according to proximity to the heart - No pulse
