Quiz 4 Flashcards
How is the velocity of blood flow related to the cross-sectional area of a blood vessel or group of blood vessels?
Velocity is inversely related to cross sectional area.
According to Ohm’s Law what 2 factors determine blood flow through a blood vessel?
q= (Pa-Pv)/R
Flow = Pressure difference/Resistance
Define blood pressure
The force exerted by the blood against any unit are of the vessel.
What is the conversion factor from mm-Hg (mercury) to cm-H2O?
1 mmhg = 1.36 cm of H2O pressure
What is cerebral perfusion pressure?
MAP - CVP or ICP (whichever is higher)
According to Poiseuille’s Law what factor has the greatest impact on the rate of blood flow through a vessel?
Radius - Varies directly as the 4th Power of the radius.
What is resistance?
The impediment to blood flow in a vessel.
Low Resistance = High Flow
High Resistance = Low Flow
Can resistance be measured directly?
Cannot be measured by any direct means. Only indirectly
What is the formula for calculating Systemic Vascular Resistance?
SVR= (MAP-CVP)/CO * 80
Normal = 700 - 1600
What is the formula for calculating Pulmonary Vascular Resistance?
PVR= (MPAP-MPAWP)/CO * 80
Normal = 100 - 300
How would you calculate resistance when blood vessels are arranged in series?
The arteries, arterioles, capillaries, venules, and veins are collectively arranged in series. When blood vessels are arranged in series, flow through each blood vessel is the same and the totalresistanceto blood flow (Rtotal) is equal to the sum of theresistances of each vessel.
How would you calculate resistance when blood vessels are arranged in series?
The arteries, arterioles, capillaries, venules, and veins are collectively arranged in series. When blood vessels are arranged in series, flow through each blood vessel is the same and the totalresistanceto blood flow (Rtotal) is equal to the sum of theresistances of each vessel.
Rt= Ra+Rb+Rc
How would you calculate resistance when blood vessels are arranged in parallel?
determined by the pressure gradient and its ownresistance, not theresistanceof the other parallel blood vessels. However, increasing theresistanceof any of the blood vessels increases the totalvascular resistance.
1/rt= 1/ra+1/rb+1/rc
If you added another blood vessel in a parallel arrangement, would total vascular resistance increase or decrease? Why?
decrease, because the total resistance of a network is less than the resistance of the single lowest resistance.
Parallel Vessels decrease TVR
What is turbulent flow?
Turbulent flow means that the blood flows crosswise in the vessel and along the vessel, usually forming whorls in the blood, called eddy currents.
What formula could you use to predict laminar versus turbulent flow?
Reynolds #
ρ = density
D = tube diameter
= mean velocity
η = viscosity
<2000 = Laminar 2000-3000 = Variable >3000 = Turbulant
What is the relationship of hematocrit to blood viscosity?
The higher the Hematocrit, the higher the blood viscosity & vice versa
What is the relationship of hematocrit to blood viscosity?
The higher the Hematocrit, the higher the blood viscosity & vice versa
Its viscosity increases at low flow velocities
What is the most important monitor in the operating room?
the fundamental basis for circulatory monitoring remains in the eyes, hands and ears of the anesthesiologist.”
Name a return-to-flow technique of blood pressure measurement.
- Palpation
- Pulse oximeter (Plethysmographic Waveform)
- Indwelling arterial catheter
Name several insertion sites for arterial catheters.
Radial Artery Brachial Artery Femoral Artery Dorsalis Pedis Artery Axillary Artery Ulnar Artery
What is damping in an arterial line tracing?
Excessive damping leads to underestimated systolic and overestimated diastolic
Underdamping leads to overestimated systolic and underestimated diastolic
What are the 3 waves seen in a normal CVP tracing?
a) wave
a is for atrium… this is the right atrial contraction.
c) wave
c is for cusp… this is the cusp of the tricuspid valve, protruding backwards through the atrium, as the right ventricle begins to contract.
It correlates with the end of the QRS complex on the ECG
v- atrial filling
What are the different waveforms that would be encountered when inserting a Swan-Ganz catheter from its insertion in the right jugular vein to its final position in a pulmonary artery?
Slide 25
What information can be gathered from a Swan-Ganz catheter?
slide 22
What are the 2 steps of “zeroing” a transducer?
Establishing a standard reference value, ambient atmospheric pressure, which is assigned the value of 0 mm Hg and used as the reference point for all subsequent intravascular pressure measurements
Based on echocardiographic data, the best transducer placement for standard clinical monitoring is at a vertical height approximately 5 cm below the left sternal border at the fourth intercostal space.
What is damping in an arterial line tracing?
Overdamping (This is defined when the oscillations following the downstroke are sluggish and can underestimate systolic pressure or overestimate diastolic pressure)
Underdamping (This is defined when the oscillations are too pronounced and can lead to a false high systolic or a false low diastolic pressure). To many oscillations on square wave test (ringing):
What is ringing in an arterial line tracing?
To many oscillations- underdampened
What is the Fick Principle method of measuring cardiac output?
Know it. Slide 33
What is the thermodilution method of measuring cardiac output?
Peak Inspiration or end expiration. 10 cc of cold saline is injected into the CVP port on the swan and the temperature change is recorded as it hits the monitor in the thermistor. The cardiac output is inversely proportional to the area under the curve
In a healthy individual with disease-free arteries, does systolic blood pressure increase or decrease in the leg relative to the proximal aorta?
Increase
