B4.048 Prework 1: Fick Principle to Measure Blood Flow

Question 1

what is the direct Fick method used for

Answer 1

measure cardiac output, pulmonary blood flow, or organ blood flow

Question 2

state the Fick equation in words

Answer 2

the amount of blood flowing though the systemic circulation (CO) is equal to the rate of oxygen consumption by the systemic organs divided by the difference in oxygen contents of systemic arterial and venous blood

Question 3

what is oxygen delivery equal to?

Answer 3

cardiac output * oxygen content in arterial blood

Question 4

what is oxygen consumption equal to?

Answer 4

CO * (systemic artery O2 content - systemic vein O2 content)

Question 5

O2 content in arteries and veins under resting conditions

Answer 5

20 ml O2 / 100 ml arterial blood

15 ml O2 / 100 ml venous blood

Question 6

what is the effect on oxygen content if blood flow is increased but rate of O2 consumption remains constant?

Answer 6

higher venous O2 content

Question 7

what is the effect on oxygen content if blood flow remains the same but rate of O2 consumption increases?

Answer 7

lower venous O2 content

Question 8

CO =

Answer 8

O2 consumption / (systemic artery O2 content - systemic vein O2 content)

Question 9

pulm blood flow =

Answer 9

O2 uptake in lung / (pulmonary vein O2 content - pulm artery O2 content)

Question 10

how is oxygen uptake from lungs measured?

Answer 10

spirometer

Question 11

how is oxygen consumption by systemic organs measured?

Answer 11

more difficult to measure than lung O2 uptake

at steady state oxygen uptake = oxygen consumption

Question 12

if there is no shunt, what is true about O2 content measurements?

Answer 12

1. O2 content in systemic venous blood is equal to that of pulmonary arterial blood
2. O2 content in systemic arterial blood is equal to that of pulmonary venous blood

Question 13

which structures contain deoxygenated blood?

Answer 13

systemic veins
RA
RV
pulm artery
O2 content is 15 in all at normal conditions

Question 14

which structures contain oxygenated blood?

Answer 14

pulm vein
LA
LV
systemic arteries
O2 content is 20 in all at normal conditions

Question 15

what happens if there is an intracardiac shunt?

Answer 15

there are 3 different O2 contents in the cardiovascular system instead of 2

Question 16

what is true of CO and pulm blood flow in the absence of a cardiac shunt?

Answer 16

they are equal

Question 17

what is true of CO and pulm blood flow in the presence of an intracardiac shunt?

Answer 17

magnitude of the shunt is equal to the difference between the pulmonary blood flow and the cardiac output

Question 18

what two important changes signify the presence of a shunt?

Answer 18

1. altered blood O2 content

2. changes in blood volume

Question 19

how is blood O2 content altered in a shunt?

Answer 19

there is abnormal change in blood O2 content of a chamber of the heart or vessel compared to that in the preceding chamber or vessel

• the area where the abnormal O2 level is first observes receives the shunt
• the blood O2 content is not changed in the area where the shunt originates

Question 20

how does blood volume change in a shunt?

Answer 20

• blood volume will be reduced in the area where the shunt originates
• blood volume will be increased in the area receiving the shunt

Question 21

VSD shunt

Answer 21

elevated O2 content in RV

Question 22

ASD shunt

Answer 22

elevated O2 content in RA

Question 23

PDA shunt

Answer 23

elevated O2 in pulm artery