Chapter 17

Question 1

what is cardiac output (Q)?

Answer 1

the amount of blood pumped by the heart in 1 minute

Question 2

how do you calculate cardiac output (Q)?

Answer 2

cardiac output = heart rate x stroke volume

Question 3

what are 3 methods to assess cardiac output?

Answer 3

1. direct fick (invasive)
2. indicator dilution (invasive)
3. CO2 rebreathing (non-invasive)

Question 4

what is the gold standard of assessing cardiac output?

Answer 4

direct fick method

Question 5

what is the direct fick method?

Answer 5

expresses relationships between VO2 (mL/min) and a-VO2 diff (mL/100mL blood)

Question 6

how do you use the direct fick method to calculate cardiac output?

Answer 6

cardiac output = VO2 / a-VO2 diff

VO2 (L/min) using open circuit spirometry

average difference between O2 content of arterial and mixed-venous blood

Question 7

how do you use the indicator dilution method to calculate cardiac output?

Answer 7

cardiac output = amount of dye injected / average dye concentration in blood for duration of curve x duration of curve

injects a known quantity of inert dye into a large vein

mixes as blood travels to lungs and returns to heart before the ejection through systemic circuit

Question 8

how do you use the CO2 rebreathing method to calculate cardiac output?

Answer 8

open-circuit spirometry method determines VCO2

can only be used during steady-rate conditions

Question 9

what is the average cardiac output for males and females?

Answer 9

males: 5L/min
females: 4L/min

Question 10

why do females have lower cardiac outputs and stroke volumes?

Answer 10

they have a smaller body and heart size

Question 11

what are 2 factors that explain large SV and low HR of endurance trained athletes?

Answer 11

1. increased vagal tone and decreased sympathetic drive, both slow the heart
2. increased blood volume, myocardial contractility, and compliance of the left ventricle

Question 12

why do endurance athletes have large maximal cardiac output?

Answer 12

because the have large stroke volume

Question 13

what are 3 mechanisms that increase the heart’s SV during exercise?

Answer 13

1. enhanced cardiac filling in diastole followed by a more forceful systolic contraction
2. normal ventricular filling with subsequent more forceful ejection and emptying during systole
3. training adaptations that expand blood volume and reduce resistance to blood flow in peripheral tissues

Question 14

what factor produces greater preload during the cardiac cycle’s diastolic phase?

Answer 14

any factor that increases venous return or slows the heart

Question 15

what is the frank-starling law? *

Answer 15

force of contraction of cardiac muscle remains proportional to its initial resting length

Question 16

what is the function of catecholamine release in exercise?

Answer 16

enhances myocardial contractile force to augment stroke power and facilitate systolic emptying

Question 17

what is the cardiovascular drift?

Answer 17

describes the gradual time-dependent downward “drift” in cardiovascular responses