Venous Hemodynamics Flashcards
how much blood is in veins
2/3
two different pressures effecting the vein shape are
intramural (internal)
interstitial (external)
compliance permits increase in the blood volume without a significant increase in the _____
venous pressure
veins are less ___ than arteries but are more ___
elastic
compliant
veins have _____ resistance to blood flow when in the supine position due to _____
little
reduced effect of gravity
the pressure difference from the post capillary vein and heart is ____
low
venous return to the heart is assisted by (4)
cardiac cycle
respiration
muscles
valves
2 periods of heart cycle increase venous flow
opening of tricuspid valve (more volume as can enter RV)
ventricular systole (pulls TV annulus down created more volume in RA for blood)
when the TV opens there is more ___ in the heart, _____ the pressure
volume
dropping
ASVD
atria contracts
ventricular systole (increased atrial V)
decreased flow as atria is filled
opening of TV
venous flow affected by movement of diaphragm is referred to as ______
respirophasicity
Valsalva maneuver increases pressure where (compared to diaphragm)
above and below diaphragm
inspiration = intra-abdominal pressures
increase
expiration = intra-thoracic pressures
increase
inspiration = IVC
collapses
inspiration = LE venous return
decrease (more pressure in abdomen)
inspiration = UE venous return
increases (less intra-thoracic pressure)
when can respiration effects be diminsed
when in supine position/with shallow breather/standing
contraction of voluntary muscles (ex.calf) results in _____ venous pressure by interrupting the ______ column of blood
decreased
hydrostatic
at rest, with no muscle activity, the veins act as _____
reservoirs for blood collection
muscle contraction = venous flow in the deep and sup veins is _____ the heart
muscle relaxation = small amount of flow occurs in the _____, from the sup to the deep veins
toward
perforators
calf pump: contraction of the ____ and ___ muscles are the most efficient
gastrocnemius
soleus
calf capacitance high generate a pressure of about ___ mmHg/contraction
200
in a single contraction of a calf muscle, ____% of the venous volume is ejected
40-60
venous valves prevent
retrograde flow
venous valves are _____ (bi/tricuspid) and arise from the ____ layer
bicuspid
intimal
vales in perforating veins direct flow from the ______ to the ____
superficial
deep veins
at the valve site, the vein ___ slightly at the sinus and ____ with increased pressure
dilates
expands
what is a frequent site of thrombi due to stagnant flow in a vein
at the sinus of valves
_____ or _______ can impede the flow of blood back to the heart from the lower extremities
gravity
hydrostatic pressure
for every 12 inches of vertical distance below the heart, there are _____ of pressure
22mmHg
hydrostatic pressure is defined by the …
weight of a column of blood at a given point
hydrostatic pressure is relative to the _______ pressure of zero
right atrial
anything above the heart has _____ hydrostatic pressure
negative
when supine, the hydrostatic pressure is ______ (about _____)
negligible
10-15mmHg
when standing, the ankle hydrostatic pressure rises to around ______ and the leg veins ____ to accept the blood pooling
110mmHg
dilate
during activity, the blood is continuously ejected by muscle contractions, _____ the hydrostatic pressure. (walking hydrostatic pressure is about ____)
reducing
25mmHg
transmural pressure determines
the cross-sectional shape of a vein
transmural pressure is the difference between _____ and _____ pressures
intraluminal
interstitial
intraluminal pressure is the pressure _____
within the vein wall
______ pressure is the pressure within the vein walls
intraluminal
interstitial pressure is the pressure _____
exerted from outside the vein by surrounding tissue and fluid
_____ pressure is the pressure exerted from outside the vein by surrounding tissue and fluid
interstitial
what happens to the vein with low transmural pressure
the vein wall collapses and becomes elliptical in shape
what happens to the vein with high transmural pressure
the vein becomes circular and may even distend at higher venous pressures
respirophasic antegrade flow is opposite in upper and lower extremities due to the changes in the ______ and ______ pressure
intrathoracic
intra-abdominal
breathing in in lower extremities = flow ___
breathing in in upper extremities = flow ____
decreases
increases
central veins are veins near what
the heart
what happens to upper and lower extremity veins when performing the Valsalva maneuver
increased thoracic and abdominal pressure = increases pressure in both upper/lower extremity veins = flow stops or diminish in both
release of breath after Valsalva maneuver will _____ or ____ flow in both the upper and lower extremities
increase
augment
what is an abnormal response of flow during Valsalva maneuver
reverse of flow
Valsalva maneuver should not be performed in patients with ____
heart disease
3 abnormal waveforms
continuos
pulsatile
reflux
continuos flow is when there is a lack of _____ usually as a result of a more ____ _____ from a ____ or _____
respirophasicity
proximal obstruction
clot
extrinsic mass
pulsatile flow is when the _______ is reflected into vessels further from the heart because of increased ______ pressure related to a heart condition
heart beat
central venous
retrograde flow is a result of ______ or _____.
valve incompetence
venous distention
a small amount of retrograde flow is _____, but if prolonged it represents venous _____
normal
insufficiency
