Unit 1 Study Guide

hematocrit

the percentage of volume of red blood cells

35-50

the normal hematocrit range is ______________

resistance

the opposition to flow

arterioles

resistance is controlled by _________________

viscosity

• a measure of a fluid’s resistance to flow

• the thickness of a fluid

• units are poise or kg/m-s

density

mass/volume (g/mL; g/cc; kg/m3)

higher

blood density is ______________ than the density of water

inertia

a measure of the resistance to acceleration of an object

volumetric flow rate

• flow is quantified by the volume that passes by any given point per time

• only applies to a straight rigid tube

vessel length, vessel radius, and viscosity

__________________ affect resistance

temporal

steady and pulsatile flow are both _______________ flow categories

steady flow

• fluid that moves at a constant speed or velocity

• blood through arterioles and peripheral veins

pulsatile flow

• non-steady flow with acceleration & deceleration over the cardiac cycle

• fluid that moves with a variable velocity

• blood through arteries, IVC, SVC

spatial

laminar, disturbed, and turbulent flow are all ____________ flow categories

laminar

___________ flow includes plug and parabolic flow

plug flow

• majority of fluid travels at the same speed

• occurs at the entrance to a vessel

• similar to the motion of a solid object that moves as a unit

parabolic flow

average velocity = ½ max velocity in the center of the vessel

disturbed flow

• streamlines persist but waver and vary

• irregular pattern which is oscillatory

• initial indication of laminar breakdown

• caused by increased velocity and altered vessel geometry

turbulent flow

• chaotic flow in many directions and speeds

• streamlines are obliterated

• vortex (swirling pattern of rotational flow)

• flow varies from instant to instant and from location to location

• flow energy converted to sound (murmurs, bruits) or vibration (thrill)

• often associated with cardiovascular pathology and increased velocities

the continuity rule

• blood is neither created nor destroyed as it flows through a vessel

• volumetric flow rate must be constant proximal, within, and distal to a stenosis

• flow speed increases at a stenosis to maintain a constant flow

• turbulence can occur distal to a stenosis

collaterals

• established in the presence of severe obstruction within an artery

• cannot completely correct the hemodynamic consequences of the obstructive lesion

parallel

collateral pathways are considered ____________ pathways

resistance

______________ in the collateralized segment is less than the obstructed vessel, but more than a normal vessel

expansion of elastic vessels

in a normal artery, the ___________________ leads to a brief reversal of flow during diastole as the pressure distally overcomes the pressure upstream because of the heart relaxing

high; low

direction of flow is from ____________ pressure to __________ pressure

expands; recoils

a compliant vessel _______________ with increased pressure and ________________ when the pressure drops later in the cardiac cycle

high

a large drop in pressure from proximal to the distal side of the arteriole indicates the arteriole’s ___________ resistance

arterioles

the highest drop in pressure occurs at the level of the ______________

transmural pressure

the pressure across the vessel wall

inversely

pressure and velocity are _____________ related

Bernoulli Effect

the decrease of pressure in regions of high flow speed is known as the ________________

inspiration

pressure in the abdominal cavity increases and pressure in the thoracic cavity decreases during ___________

expiration

pressure in the abdominal cavity decreases and pressure in the thoracic cavity increases during ___________

hydrostatic pressure

the weight of the blood pressing against the vessel wall

gravity

hydrostatic pressure comes from _______________

the weight of the column of blood from the heart to the point of measurement

hydrostatic pressure is equal to:

positive

below the heart, hydrostatic pressure is _______________

negative

above the heart level, hydrostatic pressure is _______________

superficial to deep, or from skin to heart

flow direction of veins is from:

compression of the veins by leg muscles

return of blood from legs to heart is facilitated by:

veins

___________ have generally low pressure

arterial resistance

venous resistance is approximately equal to:

reflux

• aka insufficiency

• increased venous pressure and decreased venous return

• can be caused by DVT

edema

the accumulation of abnormally large volumes of fluid in the intercellular spaces of the body

supine

in normal patients, edema will not form when _____________

limb elevation and compression stockings

treatment for edema includes:

pseudoaneurysm

a ______________ occurs when a vessel wall ruptures resulting in extravascular blood collection

cardiac cycle

the size of a pseudoaneurysm changes during each _____________

pseudoaneurysm

a ___________ occurs as a result of trauma, angioaccess grafts, or at puncture sites

pseudoaneurysm

the sonographic appearance of a ____________ includes the ying-yang color Doppler and the to and fro Doppler pattern

external compression

a fresh pseudoaneurysm can be treated with ________________

ultrasound guided thrombin injection

An older pseudoaneurysm cannot be compressed due to endothelization and requires ____________________

Reynold’s Number

the likelihood of turbulence is expressed in terms of __________________

2000

a RE above ______________ indicates turbulent flow