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Cardiovascular > Exercise: Pathophysiology and Testing > Flashcards

Exercise: Pathophysiology and Testing Flashcards

1
Q

What are determinants of maximal oxygen uptake? (name 5)

A
  1. Genetics
  2. Training
  3. Age
  4. Gender
  5. Environment (heat, altitude)
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2
Q

What does the fick principle say?

A

Amount of a substance removed from or taken up by an organ per unit time = arterial - venous concentration of substance x organ blood flow

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3
Q

Why is the Fick Principle important?

A

Connects respiratory VO2 (oxygen consumption) with oxygen delivery (circulatory system) and oxygen extraction (skeletal muscle)

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4
Q

What is the fick equation?

A

CO x (Ca-Cv)O2 = VO2

Cardiac output x difference between arterial and venous O2 equals oxygen consumption

CO = cardiac output
Ca = O2 content in arteries
Cv = O2 content in veins

CaO2 or CvO2 = [Hgb] x 1.34 x O2 saturation (5)

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5
Q

What does the difference between O2 content in arteries and the O2 content in the veins measure?

A

Ability to extract O2

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6
Q

CO = HR x _____

A

SV

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7
Q

What influences HR?

A

SNS increase HR, PNS decreases HR

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8
Q

What influences SV?

A

SNS increases contractile strength which increases SV, higher mean arterial pressure decreases SV, increased end diastolic volume increases SV

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9
Q

What are the x and y axis on the frank starling curve?

A

X is Stroke Volume, Y is Ventricular End-Diastolic Pressure.

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10
Q

What does the frank starling relationship show?

A

As you increase ventricular end-diastolic pressure, you increase stroke volume until a certain point. The curve levels out which shows that after a while, increasing pressure will no longer help increase stroke volume and patients start to present with negative symptoms

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11
Q

What are the major adjustments of circulatory system during exercise? (3 things)

A
  1. Increased blood flow (cardiac output or muscle blood flow)
  2. Redistribution of blood flow (from inactive organs to active skeletal muscle)
  3. Maintaining blood pressure (driving force of blood flow, maintains blood flow to vital organs (brain)
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12
Q

True or False: At rest, most of your blood isn’t being used.

A

True. About 64% of your blood volume sits in veins at rest and isn’t being used. This is a large reservoir that can be made available to meet increased need

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13
Q

What is avg resting bpm and what autonomic control is this under?

A

60-80bpm (28-40 in endurance athletes). This is under parasympathetic control

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14
Q

What is the anticipatory response?

A

This is when you know you’re about to exercise and your HR increases just prior to exercise. This is caused by the Central Command from CNS and is a component of sympathetic activity.

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15
Q

During exercise, increase in HR is proportional to _____

A

exercise intensity

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16
Q

True or False: During exercise, there is a linear response up to near maximal exercise.

A

True

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17
Q

True or False: a person’s maximal heart rate is variable

A

False. It is highly reproducible and consistent

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18
Q

Age influences a person’s maximum heart rate. What is the equation to calculate the age related maximum HR?

A

220-age is a rough estimate of max HR. After age 15, max HR decreases by 1 bpm per year

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19
Q

When doing early exercise (100bpm), what is happening with the autonomic nervous system?

A

Parasympathetic withdrawal

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20
Q

When doing moderate to heavy exercise, what is happening with the autonomic nervous system?

A

Sympathetic stimulation

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21
Q

What’s the difference between increasing HR with exercise vs. artificially?

A

Artificial increase of heart rate results in a drop in stroke volume. With exercise, heart rate increases but so do a lot of other things. With exercise, you have vasodilation, increased venous return, venoconstriction, preservation of ventricular filling.

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22
Q

What happens when you exercise?

A

Increased HR, vasodilation, increased venous return, venoconstriction, preservation of ventricular filling.

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23
Q

What 3 factors influence SV during exercise?

A
  1. Preload (affected by venous return, ventricular distensibility, pericardial constraint)
  2. Contractility
  3. Afterload (avg aortic or pulmonary pressure)
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24
Q

Do athletes typically have higher or lower pericardial compliance?

A

Higher. This helps them accommodate higher stroke volume during exercise

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25
Q

What factors influence venous return? (name 3)

A
  1. Venoconstriction
    - reflex sympathetic control of vascular smooth muscle happens in the majority venous return channels (veins, venues, venous sinuses)
  2. Muscle pump
    - acts like a second heart during upright exercise. Increases venous return
  3. Respiratory pump
    - Major factor for venous return in upright exercise. Negative thoracic pressure increases venous return
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26
Q

What factors influence ventricular contractility? (2 factors)

A
  1. Sympathetic nervous system
    - direct innervation
    - circulating catecholamines (norepinephrine, epinephrine)
    Frank Starling Effect
    - increased stretch leads to enhanced contractility
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27
Q

How much stroke volume augmentation occurs when exercising?

A

Standing exercise - 40-60% increase

Supine exercise - 20-40% increase

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28
Q

Do patients with sedentary lifestyles or endurance athlete lifestyles have greater SV?

A

Endurance athletes have greater SV both at rest and during exercise

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29
Q

In sedentary patients, stroke volume plateaus after about 50% of maximal exercise. How about in elite athletes?

A

In elite athletes, there isn’t a plateau. SV continues to rise until maximal exercise.

30
Q

What are the mechanisms behind athletes having better stroke volume response to exercise? (2 mechanisms)

A
  1. Increase in EDV with enhanced starling forces at lower workloads
  2. Increase in contractility with lower ESV at higher workloads
31
Q

True or False: Increase in cardiac output is independent of metabolic rate required to perform the exercise.

A

False. Cardiac output is directly proportional to metabolic rate required to perform the exercise. There is a linear relationship between cardiac output and % VO2 max

reminder: VO2 max is the maximum oxygen uptake

32
Q

What is the cardinal rule relating cardiac output an increased O2 uptake?

A

6L/min of cardiac output is required for each 1 L/min increase in O2 uptake above rest.

33
Q

In upright exercise, if exercise is only at

A

HR and SV

34
Q

In upright exercise, if exercise is >50% VO2 max, what increases?

A

Only HR. Unless you’re an elite athlete–then SV increases too

35
Q

True or False: After age 50, maximal cardiac output decreases in a linear fashion in both men and women–due to decrease in maximal HR

A

False. It’s after age 30 that maximal cardiac output starts to decrease in a linear fashion in both men and women. (decrease in max HR)

36
Q

True or False: Athletes have a higher resting cardiac output than untrained individuals.

A

False. The cardiac output is the same in everyone. However, athletes have greater SV and slower HR (training induced bradycardia). But with a greater SV and slower HR, the overall CO is still the same as in an untrained individual.

37
Q

What is the resting cardiac output for men? for women?

A

Male 5 L/min

Female 4.5 L/min

38
Q

True or False: Athletes have a higher exercise cardiac output than untrained individuals.

A

True. While athletes and untrained individuals have the same CO at rest, during exercise, athletes have greater cardiac output because their SV keeps increasing as VO2 increases while untrained individuals SV peak at about 50% VO2 max.

39
Q

What is the exercise cardiac output for men? for women?

A

About 4-5 fold increase
Male ~22L/min
Female ~18L/min

40
Q

During exercise, what happens to blood pressure and vascular resistance?

A

Vascular resistance is decreased but blood pressure is increased.

The decrease in vascular resistance is from vasodilation and this allows there to be an increase in blood flow.

The increase in Systolic blood pressure is related to the increase in cardiac output (increased SV and HR).

If there was a rise in blood pressure alone, this would increase vascular resistance and decrease blood flow (counterproductive)

41
Q

Vessel diameter is important for blood flow during exercise. What two factors influence vessel diameter during exercise?

A
  1. Sympathetic nervous system

2. local blood flow regulation (auto regulation)

42
Q

True or False: Blood viscosity is an important factor during exercise

A

False. It’s not a major factor during exercise.

43
Q

What influences blood viscosity?

A

RBC concentration

44
Q

What is Mean Arterial Pressure?

A

It’s the average blood pressure during a cardiac cycle. It’s not just an average of systolic pressure and diastolic pressure because more of the cardiac cycle is spent in diastole. So, it’s calculated as follows:

MAP = DBP + 0.33 (SBP-DBP)

45
Q

What is Systolic BP?

A

The pressure generated as blood is ejected from the LV

46
Q

What is Diastolic BP?

A

The pressure during ventricular relaxation, reflection of compliance of vascular bed.

47
Q

What is pulse pressure?

A

The difference between SBP and DBP

48
Q

How do systolic, diastolic, and mean arterial pressure change in response to exercise?

A

Systolic BP increases
Diastolic BP stays the same
MAP increases (bc of systolic increase)

49
Q

What is the estimated blood flow to skeletal muscle during rest compared to during exercise?

A

Rest: 15-20% of CO

Exercise 80-85% of CO

50
Q

What happens to splanchnic blood flow (liver, kidneys GI) when exercising?

A

Decreases in response to increase in muscle blood flow – function of % VO2 max

51
Q

What happens to Brain Blood Flow during exercise?

A

Absolute blood flow is slightly increased but percent of total CO is decreased

Rest: 15% of 5 L/min = (0.75 L)
Exercise 3-4% of 25 L/min = (0.875 L)

Absolute blood flow is in parenthesis.

52
Q

How is blood flow from non-exercising vascular beds redistributed to skeletal muscle?

A

There is vasoconstriction in the non-exercising vascular beds which is increased by SNS activity. This is regulated by muscle ergo receptors and the cardiovascular control center in the medulla. The intensity of the exercise will determine the # of motor units recruited which can signal to the SNS to increase or decrease vasoconstriction in the non-exercising vascular beds.

53
Q

What happens to the vascular beds in exercising muscle?

A

Vasodilation. This is under intrinsic metabolic control (decreased PO2, increased PCO2, nitric oxide, K+, acidosis, adenosine)

Regulation occurs at the level of arterioles and small arteries (as opposed to the vasoconstriction in the veins to bring blood back to the heart)

Capillary recruitment occurs in skeletal muscles. Typically only 5-10% of capillaries in skeletal muscles are open at rest but during exercise that increases to nearly 100%. This increases vascular surface area for oxygen delivery and extraction

54
Q

What is sympatholysis?

A

Typically, the increase of sympathetic nervous system causes vasoconstriction. However, sympatholysis is the term given to what happens in exercise where vasodilation of the arteries actually overpowers the typical vasoconstriction of SNS. This helps maintain the mean arterial pressure when blood flow is increased by higher cardiac output and vasoconstriction in non exercising vascular beds.

55
Q

What can happen to sympatholysis in very high stress exercise?

A

There is a large amount of active muscle mass and muscle dilation exceeds the cardiac pump capacity (drop in BP). So, sympathetic mediated vasoconstriction occurs to preserve MAP. (limits sympatholysis occurring in exercising muscle beds). This is important for preserving MAP to provide blood flow to vital organs like the brain.

56
Q

What are potential mechanisms to increase availability of O2 to exercising muscle? (3)

A
  1. Increase in oxygen delivery (supply)
  2. Increase in oxygen extraction (utilization)
  3. Increased metabolic efficiency of skeletal muscle
57
Q

What is the equation for O2 delivery?

A

O2 delivery = Flow x (arterial)O2 Content

Flow = cardiac output (systemic), or if looking at local place just the flow through the area (e.g. leg blood flow)
O2 Content = [HGB] x 1.36 x O2Saturation (%)

If you have anemia, HGB is low. If you’re at elevation and not used to it, you have lower O2 sat. These are things that would decrease O2 content => lower O2 delivery

58
Q

What is PaO2?

A

Partial pressure of oxygen. This is the driving force of tissue oxygenation

59
Q

What is CaO2?

A

This is oxygen content. This is the bulk quantity of deliverable O2

60
Q

What is SaO2?

A

This is the saturation. Which represents the relative quantity of O2. (content/capacity (%))

(this is how much O2 is able to saturate your maximum capacity. E.g. if 100% saturation, the content = capacity)

61
Q

What is a-v O2?

A

This is the oxygen extraction–the difference between the O2 in arteries and O2 in veins.

62
Q

What is the av O2 at rest? during exercise? Interpret this difference

A

4-5 vol% at rest, 15% during exercise

There is, roughly, a 3 fold increase in av O2 when exercising compared to rest. However, remember that there is a 5 fold increase in blood flow (CO and muscle blood flow) with exercise. So, the 3 fold increase in extraction has a lot to do with higher quantity of blood flow, not necessarily higher ability for oxygen extraction.

Take-away point is that increased blood flow during exercise is very important for increasing oxygen extraction

63
Q

What is the primary way to increase O2 delivery to the heart during exercise?

A

Increase of coronary blood flow. The increase in O2 extraction ability is increased during exercise but it’s not the main cause for increase of O2 delivery to the heart during exercise.

Remember: O2 sat after extraction (CV O2sat) during rest is 25% and during exercise this can go down to 10% because the extraction ability is increased. However, the point of this is that the primary way to increase O2 delivery to the start is still increasing coronary blood flow.

64
Q

What is the CV O2 saturation after extraction in coronary blood flow? (coronary venous)

A

25% (and down to 10% during exercise). The heart is very good at extracting oxygen. In systemic blood flow, it’s only extracted down to about 65%.

65
Q

What is RPP (rate pressure product)?

A

HR x BP

66
Q

What is the most influential factor for RPP?

A

Heart rate!

RPP = HR x SBP
RPP = HR x CO x SVR
RPP = HR x HR x SV x SVR
RPP = HR^2 x SV x systemic vascular resistance
67
Q

What does RPP tell you?

A

Myocardial Oxygen Demand

68
Q

How can you use RPP as a sign of ischemic threshold?

A

You can increase the workload during a stress test while tracking RPP. When you start seeing ST depression on the ECG, you can know that that RPP is the limit of myocardial oxygen demand that the O2 delivery can keep up with.

69
Q

How can you tell if you have a coronary stenosis vs coronary vasomotion?

A

In coronary stenosis, you will have a fixed RPP at which there is ischemic threshold. If you have abnormal coronary vasomotion, you will have variable RPP at which you find the ischemic threshold.

70
Q

True or False: More severe ischemia occurs at higher RPPs.

A

False. The more severe the ischemia, the lower the RPP of the ischemic threshold.

71
Q

What does beta blocker therapy do to RPP?

A

Beta blockers lower RPP significantly. Remember that the most influential factor for RPP change is heart rate.

72
Q

What happens to RPP with athletic people?

A

RPP drops. Athletic people have lower heart rate. Remember that the most influential factor for RPP change is heart rate.

Cardiovascular (22 decks)

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