Cardiac Output

Question 1

How can resting cardiac output be estimated?

Answer 1

0.08 x body weight

Question 2

What is the most accurate method of measuring cardiac output?

Answer 2

Using a flow probe

Question 3

What vessel is most frequently used with a flow probe to access cardiac output and why?

Answer 3

Pulmonary artery because it is more superficial and easier to access than the aorta

Question 4

What are the two types of flow probes?

Answer 4

Electromagnetic flow probe and dopplerflow probe

Question 5

What does an electromagnetic flow probe measure?

Answer 5

Velocity of ions in the blood

Question 6

What formula is used to calculate the flow using an electromagnetic flow probe?

Answer 6

Velocity (length/time) x Cross-Sectional Area (length2) = Flow (length3/time)

Question 7

How does a doppler flow probe measure cardiac output?

Answer 7

RBCs in circulation reflect UV waves at a frequency different than the emitted frequency and the change in frequency is dependent on RBC velocity

Question 8

What does the Fick principle say?

Answer 8

Extraction= Arterial [x]- venous [x]

Question 9

What is the formula for calculating the uptake of X?

Answer 9

Uptake of X= BF * (Arterial[x]-venous[x]) OR Uptake= extraction * blood flow

Question 10

What is the formula for calculating the extraction of x?

Answer 10

Extraction= Arterial [x]- venous [x]

Question 11

What is the formula for calculating the % extraction for x?

Answer 11

% x extraction= (Arterial[x]- venous[x])/ arterial[x]

Question 12

If measuring the uptake of oxygen, where would the venous oxygen concentration be measured?

Answer 12

Pulmonary artery

Question 13

What is the formula for calculating cardiac output using oxygen concentrations?

Answer 13

CO = uptake O2(O2 consumption) / (Art [O2] – Ven [O2])

Question 14

What is the gold standard for measuring cardiac output?

Answer 14

Calculations using the Fick principle

Question 15

How can the cardiac output be calculated using the indicator dilution technique?

Answer 15

Volume= Initial mass of dye/ final [dye]

Question 16

What effect will a higher CO have on the amount of time is takes to circulate dye using the indicator dilution technique?

Answer 16

A higher CO will circulate the dye in a shorter amount of time

Question 17

What serves as an indicator when calculating cardiac output using thermodilution?

Answer 17

Temperature

Question 18

What kind of catheter is used in thermodilution? How many ports does it have?

Answer 18

Swan Ganz catheter with 4 ports

Question 19

What port of the Swan Ganz catheter measures the pressure at the tip of the catheter?

Answer 19

Distal port

Question 20

Where does the proximal port of a Swan Ganz catheter open into? What is this port used for in thermodilution?

Answer 20

Right atrium; inject cold saline into the right atrium through the proximal port

Question 21

What is the function of the thermistor in thermodilution?

Answer 21

Measures blood temperature

Question 22

What is the function of the balloon in thermodilution?

Answer 22

Can be inflated or deflated to direct the catheter to where you want it to go

Question 23

How can radioisotopes be used to estimate ventricular volume?

Answer 23

Radioisotopes are injected into the bloodstream. The radioactivity would be measured in diastole vs. systole. The difference would tell you about stroke volume