BP stuff

Question 1

What is the test called that assesses the damping coefficient?

Answer 1

“square wave”
“fast flush test”

Question 2

Fill in the blanks

Answer 2

Question 3

What determines the diastolic arterial pressure?

Answer 3

• blood viscosity
• arterial distensibility (i.e., compliance)
• length of the cardiac cycle

Question 4

What determines the systolic arterial pressure?

Answer 4

• stroke volume
• arterial compliance
• ejection velocity of the LV
• SVR
• left ventricular preload

Question 5

Explain what causes the dicrotic notch

Answer 5

elastic recoil of the arteries after the aortic valve closes causes the upspike

Question 6

In what condition can the dicrotic notch dissapear?

Answer 6

vasoconstriction (i.e., arterial elasticity will go down)

overdamping

Question 7

How does the pressure waveform change when arterial BP is measured further away from the center?

Answer 7

• upstroke becomes steeper
• higher SAP
• dicrotic notch appears later in the downstroke
• lower DAP

i.e., underdamping
e.g., long tubing

Question 8

How does the MAP change when moving the dABP measurement more peripherally?

Answer 8

does not change, even though pulse pressure increases, MAP remains fairly constant

Question 9

How does the SAP change during inspiration and expiration in mechanical ventilation

Answer 9

remember overall: decreased BP

BUT:
* inspiration –> increased intrathoracic pressure –> increased LV preload and decreased afterload –> increased LV SV and SAP
* expiraiotn –> decreased SV –> decreased SAP

Question 10

How much is the pulse pressure variation from inspiration and expiration normally?

Answer 10

5 mm Hg difference - not clinically significant

Question 11

What are the 2 ways to obtain MAP?

Answer 11

• machine averages the area under the pressure waveform from several beats
• MAP = DAP + (SAP-DAP)/3

Question 12

In what situation does the traditional MAP equation underestimate MAP?

Answer 12

tachycardia
–> less diatolic filling time
MAP is closer to SAP in this scenario

Question 13

Name the systolic pressure variation equation

Answer 13

Question 14

What systolic pressure variation indicates volume responsiveness?

Answer 14

over 10 mm Hg in people
over 4.5 mm Hg in dogs

i.e., check for hypovolemia or pericardial effusion

Question 15

What is the equation for pulse pressure variation?

Answer 15

Question 16

What pulse pressure variation cutoff indicates fluid responsiveness in dogs?

Answer 16

PPV > 11-16%

Question 17

How does pulse contour analysis work?

Answer 17

Measurement for cardiac output
computation of the area under the systolic portion of the arterial waveform

need initial calibration to a known cardiac output (e.g., thermo or lithium dilution)

Note: not correlating well in veterinary patients compared to other CO measurement techniques

Question 18

What are causes of overdamping? What pathophysiology can look like overdamping?

Answer 18

• air bubbles
• too compliant tubing
• line occlusion from kinking or clotting

Hypotension if significant –> decreased SV and vasoconstriction

Question 19

List potential causes for tall and narrow blood pressure waveforms? “waterhammer pulse”

Answer 19

• decreased blood viscosity (e.g., dilutional anemia)
• peripheral vasodilation (e.g., sepsis)
• hypertension
• aortic regurgiation
• PDA

Question 20

Explain how doppler BP measurements works

Answer 20

• doppler probe with piozoelectric crystals –> placed over artery
• emits ultrasonic wave and tissue reflects it back –> probe converts this frequency shift into an audible sound
• sphygmomanometer proximal to the doppler probe
• inflate cuff until no sound is heard –> gradually deflate until sound returns = SAP

Question 21

What are the advantages and disadvantages of Doppler BP readings

Answer 21

Advantages:
* cheap
* relatively easy to set up and perform

Disadvantages:
* cannot determine DAP or MAP
* poor agreement with iBP in dogs < 5jg –> poor sensitity to detect hypotension
* cats: SAP correlates better with MAP or callibration adjustment SAP read + 14 mm Hg

Question 22

Explain how oscillometric BP measurements work

Answer 22

cuff over artery connected to a device sensing oscillations causing by blood flowing through vessel

cuff is inflated –> occludes blood flow –> deflated –>
* SAP: oscillations start increasing
* MAP: oscillations the strongest
* DAP: oscillations start decreasing

Question 23

What are advantages and disadvantages of oscillometric BP measurements?

Answer 23

Advantages:
* faster than doppler
* less technical skills needed than doppler

Disadvantages
* DAP and SAP may not be as reliable because calculated from algorithm from MAP