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2023 Systems Phys > Respiratory - Systemic/Pulmonary Circulation > Flashcards

Respiratory - Systemic/Pulmonary Circulation Flashcards

1
Q

Systemic circulation pathway

A

LV -> aorta -> body

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2
Q

Pulmonary circulation pathway

A

RV -> main pulmonary artery -> lungs

The lungs receive the entire right ventricular cardiac output

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3
Q

What are the 2 pathways of circulation in the pulmonary pathway?

A

Pulmonary Circulation
Bronchial Circulation

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4
Q

Define:

Pulmonary Circulation

What is its job? What feeds it?

A

Job: Perfuse alveoli for gas exchange
Arises from R
Receives 100% RV output

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5
Q

Define

Bronchial Circulation

What is its function? What feeds it?

A

Job: Meet the needs of the lung similar to coronaries for the heart - nourishes conducting airways and parenchyma up to terminal bronchioles
Arises from the aorta
Part of the systemic circulation
Receives 2% of LV output

Everywhere that needs O2 but no gas exchange

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6
Q

How does the bronchial circulation function?

A

Blood from bronchial circulation (deoxygenated) mixes with O2 - enriched blood in the pulmonary vein; contributes to the small A-a O2 difference

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7
Q

Characteristics of Pulmonary Circulation

Flow/Pressure/Resistance/Compliance

A

High Flow
Low Pressure
Low resistance
High compliance

Pulmonary Flow =. Systemic Flow

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8
Q

Why is the pulmonary circulation low pressure?

A

Only need to pump to top of the lungs
RV is weak
Not as much redirection of blood

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9
Q

Why is resistance lower in the pulmonary circulation?

A

Pulmonary arteries shorted, in dilated state (lg diameter)
Pulmonary arterioles are thin walled, have less smooth mucle and lower resting tone
More distensible (7X more compliant)
Enormous number of capillaries, in unique arrangement to create sheets of blood flowing past alveoli

High compliance = less work, relied on weak pump RV

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10
Q

What are the 3 factors that alter pulmonary vascular resistance?

A

Changes in blood flow (perfusion)
Changes in lung volume
Changes in local O2 concentration

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11
Q

How does changing blood flow affect pulmonary vascular resistance?

A

Increase pulmonary artery pressure -> decrease pulmonary vascular resistance (PVR) due to recruitment and distention

Open more artiers to stop increasing resistance

Exercise

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12
Q

How does changing lung volumes affect Pulmonary Vascular Resistance?

A

Pulmonary resistance follows a U shape curve with resistance lowest at FRC

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13
Q

How do changes in local O2 concentration affect PVR?

A

Hypoxia (low O2) causes constriction

opposite of systemic smooth muscle

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14
Q

What is the major difference between the pulmonary and systemic circulation?

A

Pulmonary vsculature is not significantly regulated by ANS

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15
Q

What is the relationship between CO, Pulmonary Blood Flow, and Resistance?

A

Increase CO (exercise) -> Increase PBF -> increase resistance

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16
Q

Capillary recruitment

A

All available vessels not open at rest (esp. at apex) b/c low perfusion pressure

Helps decrease Resistance

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17
Q

Capillary distention

A

Increase diameter with minimal pressure

Help decrease R

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18
Q

What are the two types of pulmonary vessels?

A

Extra-alveolar (arteries, veins)
Alveolar (arterioles, caps, venules)

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19
Q

What influences extra-alveolar vessels?

A

Not influences directly by PA due to location
Subject to Pip

Far from alveoli

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20
Q

What influences alveolar vessels?

A

Capillaries within interalveolar septa
Subject to PA

close to alveoli - increase alveoli size, increasse R

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21
Q

Inspiration

At high lung volumes…

Pip/Extra-alveolar/Resistance

A

Pip more negative -> increase transmural pressure -> distended extraalveolar vessels -> Decreases resistance
Increase alveolar diameter, crushing alveolar vessels (increase R)

Experience resistance

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22
Q

Expiration

At low lung volumes

Pip, alveolar diameter, extraalveolar vessels

A

Pip more positive - compresses extra alveolar vessels (Increase R) -> Alvelar diameter decreases (Decrease R)

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23
Q

Where is PVR lowest? When does it increase?

A

PVR is lowest at FRC and increases at lower and high lung volumes

resistance additive because vessels are in series

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24
Q

Define

Hypoxia

A

Low O2 in alveoli

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25
Q

Define:

Hypoxemia

A

Low O2 in blood -> triggers vasoconstriction

No dilation (Hypoxic vasoconstriction)

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26
Q

Why would we want to deliver blood to a region of lung that has low O2?

A

We want to match ventilation and perfusion

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27
Q

O2 influences..

A

Vascular Diameter

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28
Q

CO2 influences

A

Airway diameter

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29
Q

In an upright person, blood flow is highest…and lowest..

A

Highest near the base and lowest near the apex

gravitational effect contributes to uneve distribution of BF

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30
Q

When leaving the pulmonary artery, blood must…

A

travel up to the apex

Every 1 cm above heart, hydrostatic pressure in the arterials dropos

gravity effects blood flow in the veins too

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31
Q

Regional distribution of blood flow in the lungs is due to:

A

Effects of gravity on hydrostatic pressure
Influence of alveolar pressure on alveolar vessels

Lungs divided into 3 zones based on pressure affects on capillaries

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32
Q

Pressures affecting pulmonary blood flow

Zone 1

What is it? Characteristics , occurance, etc.

A

Apex
occurs when PA> Pa
Pulmonary capillaries collapse; no flow
created when alveolar pressure is increased (positive pressure ventilation) or arterial pressure is decreased (hemorrhage)

Increases alveolar dead space: ventilated, not perfused

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33
Q

Pressures affecting pulmonary blood flow

Zone 2

What is it? What happens here?

A

Middle 1/3 of lung
Primary area of distension, recruitment of vessels during exercise
Flow increases enough to pass alveoli
Pa > PA -> drives flow
PA > PV, PA partially collapses downstream capillarieis

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34
Q

Pressures affecting pulmonary blood flow

Zone 3

What is it? What occurs here?

A

Pa > Pv > PA
Optimal gas exchange; V/Q = 0.8-1.0

Normal Pressure

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35
Q

Define

Bulk Flow

What is it? What causes it? When does it occur?

A

How gas moves in airways from trachea to alveoli
Due to mass movement - like water out of faucet
Occurs when there are differences in total pressure

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36
Q

Define

Diffusion

What is it? Why?

A

How gas moves in us from air -> liquid; liquid -> air
gases moving due to their individual pressure gradients

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37
Q

What 2 factors determine gas diffusion?

A

Diffusion properties of membrane (Fick’s Law)
Pulmonary Capillary Blood Flow

Fick’s law- Vgas = [AxDx(P1-P2)]/T

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38
Q

Fick’s Law of Diffusion

Diffusion of a gas across a sheet of tissue is dependent on:

A

Partial Presure Gradients (ΔP)
Surface area of membrane (A)
Thickness of membrane (T)
Diffusion constant (D) - solubility of gas/MW

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39
Q

Fick’s Law of Diffusion

According to Fick’s Law, kwhat is the major determinant of rate of diffusion of a gas?

A

Partial Pressure gradients (ΔP)

40
Q

Fick’s Law of Diffusion

Rate of diffusion increases, as partial pressure…

A

increases

41
Q

Fick’s Law of Diffusion

Rate of Diffusion increases, as surface area…

A

Increases

42
Q

Fick’s Law of Diffusion

Rate of Diffusion increases, as thickness…

A

Decreases

Increase thickness, decrease rate

43
Q

Fick’s Law of Diffusion

Rate of diffusion increases, as the diffusion constant…

A

Increases

44
Q

Fick’s Law of Diffusion

What might cause thickness of the membrane to increase?

A

Edema
Pneumonia
Fibrosis

45
Q

O2 is found in the blood in what two forms?

A

Physically dissolved
Bound to Hemoglobin (Hb)

46
Q

Transport of O2 in Blood

Physically Dissolved

A

O2 is poorly soluble in body fluids
Amount dissolved is directly proportional to PO2
Makes up about .3 mL of total O2 content in arterial blood

47
Q

Transport of O2 in Blood

Bound to Hemoglobin (Hb)

A

O2 bound to Hb does not contribute to PO2 in blood
Enhances carrying capacity of blood
Most O2 is bound to Hb (98.5%, 19.7 mL/20)

Binding is reversible

48
Q

What does Blood PO2 measure?

A

The portion of O2 dissolved in the blood

It is not a measure of total O2 content in blood

49
Q

Transport of O2 in Blood

Oxyhemoglobin

A

Hb with bound oxygen
can have up to 4 O2 on 1 Hb -> saturated

bright red

50
Q

Transport of O2 in Blood

What is the importance of Saturated Hb?

A

It is relatively unstable and easily releases O2 in regions where the PO2 is low

51
Q

Transport of O2 in Blood

Deoxyhemoglobin

A

Non-O2 bound Hb

Deep maroon

52
Q

The amount of HbO2 is a function of

A

PO2 in blood

53
Q

When blood PO2 is high, what happens to Hb?

A

Form HbO2 (increased % saturation)

54
Q

When blood PO2 is low, what happens to Hb?

A

O2 is released from Hb

Decreased % saturation

55
Q

The PO2 is the primary factor determining…

A

the % Hb saturation

56
Q

Define

SO2

A

% saturation of Hb with O2
(O2 actually bound to Hb/Potentially bound to Hb) x 100

57
Q

What effect does O2 binding have on Hb?

A

Binding of O2 to each heme group increases affinity of the Hb to bind additional O2

58
Q

What is it?

The Oxyhemoglobin Dissociation Curve

A

How plasma PO2 affects O2 loading and unloading from Hb

59
Q

What does P50 mean?

A

Hb is 50% saturated

60
Q

Advantages of S shaped curved:

Plateau

A

Enables O2 to saturate Hb in lungs (high PO2)
At a PO2 of 60, Hb is 90% percent
Increases above 60, hve minor effect on Hb sat

If PO2 drops from 100 -> 60, Hb sat still 90%

Large range of PO2 Hb can still be loaded

61
Q

Advantages of S shaped curved:

Steep

A

Gives up large amounts of O2 in tissues

Small change in PO2 that leads to large drop in HbO2

62
Q

Hb results in a large net transfer of O2 by…

A

Keeping PO2 low

63
Q

Blood PO2 depends only on….

A

Concentration of dissolved O2

64
Q

Hb acts as a…

A

storage depot for O2

65
Q

How does Hb interact with O2?

Why is it important?

A

Hb acts as a storage depot for O2, removing it from solution as soon as it enters blood from alveoli
allows more O2 to enter blood

Once bound to Hb, O2 molecules no longer exert any pressure

66
Q

Oxyhemoglobin Dissociation Curve

A shift in either direction has the greatest effect on which phase?

A

Steep

67
Q

Oxyhemoglobin Dissociation Curve

Right Shift

What effect does it have to HbO2 binding? What does it do?

A

Decrease in Hb’s affinity for O2
Increase in P50 (when 50% of Hb is saturated with O2
Aids in release/unloading of O2

68
Q

What factors besides PO2 can shift the oxyhemoglobin dissociation curve?

A

CO2
Acidity
2,3 diphosphoglycerate
Exercise
Temperature

CADET face right -> factors shift curve right

69
Q

Why is CO so dangerous to us?

A

CO and O2 compete for Hb binding sites
CO out competes CO2 and shifts the curve to the far left -> inhibiting the unloading/delivery of O2 to tissues

70
Q

What 3 ways is CO2 transported in the blood?

A

As bicarbonate ions (main transporter)
Physically dissolved
Chemically bound to Hb

Total CO2 content in arterial blood is 59 mL CO2/100 mL blood

71
Q

What tells us how much O2 is in the blood?

A

CaO2

To answer “how much” need to know how much O2 bound to Hb

CaO2 - total O2 content in blood; given by SaO2 and Hb content

72
Q

What does PaO2 tell you?

A

O2 molecules dissolved in plasma
adequacy of gas exchange within the lungs when it is subtracted from calculated PAO2

73
Q

What does SaO2 tell you?

A

Heme sites occupied by O2 (saturated)
The % of all the available heme binding sites saturatrd with O2
Mainly determined by PaO2

74
Q

What does CaO2 tell you?

A

Directly reflects the totaly number of O2 in arterial blood (bound and unbound)
incorporates Hb content

Calculate by oxygen content equation

75
Q

PaO2 is determined by…

A

PAO2 and the state of alveolar capillary membrane (not by amount of Hb available to soak up)

76
Q

PaO2 determines…

A

the O2 saturation of Hb

77
Q

What determines the total amount of O2 in blood or CaO2?

A

The SaO2, the concentration of Hb, and PaO2

78
Q

On one visit, a patient has a PaO2 of 85 mmHg, an SaO2 of 98% and a Hb of 14 gm/dlm. One year later, her Hb is 7 gm/dl. Assuming no lung disease, what will her new PaO2, SaO2, and CaO2?

A

PaO2 unchanged, SaO2 unchanged, CaO2 reduced (half)

79
Q

Which patient is more hypoexemic?
A: PaO2 85 mmHg., 85% SaO2, 95% Hb 7 gm%
B: PaO2 55 mmHg, SaO2 SaO2, Hb 16 gm %

Total O2

A

A: PaO2 85 mmHg., 85% SaO2, 95% Hb 7 gm%

80
Q

APEX Summary

A

Decreased Blood flow
Decreased ventilation
Increased V/Q ratio
PaO2
PaCo2

81
Q

Base Summary

A

Increased blood flow (over perfused)
Increased ventilation
Decreased V/Q ratio
Decreases PaO2 (blood not fully oxygenated)
Increases PaCO2

82
Q

The functional importance of V/Q ratios is…

A

Matching regional ventilation to blood flow

83
Q

Alveolar (A) - arterial (a) difference in PO2

A

Measure of gas exchange efficiency across alveolar-capillary membrane

PAO2 - Calculated, PaO2 - measured

84
Q

Normal P(A-a)O2: < 20 mmHg. What causes this?

A

Normal V/Q mismatch
Return of bronchial and coronary blood (deoxygenated) through the thesbian veins to the left side of her heart

85
Q

_ helps determine cause of hypoxia

A

A-a O2 gradient

86
Q

What are the 5 causes of Hypoxemia?

A

Hypoventilation
Low inspired O2
Right-to-left-shunt
V/Q mismatch
Diffusion impairment

87
Q

Hypoventilation

A

Not ventilating well

88
Q

When would you have low inspired O2, resulting in low PO2.

A

High altitude

89
Q

How does the right-to-left shunt work?

A

Send deoxygenated blood into oxygenated

90
Q

Hypoxemia: Effects on PaO2, increasing A-aO2 difference, FiO2 = 1.0

Hypoventilation

A

PaO2 = decreased
Inc to A-aO2 difference = no (unchanged)
FiO2 = Increased

FiO2 = fraction of O2 in inspired air

91
Q

Hypoxemia: Effects on PaO2, increasing A-aO2 difference, FiO2 = 1.0

Low PIO2

A

PaO2 = decreased
Inc to A-aO2 difference = no (diffusion unchanged)
FiO2 = Increased

FiO2 = fraction of O2 in inspired air

92
Q

Hypoxemia: Effects on PaO2, increasing A-aO2 difference, FiO2 = 1.0

Right-to-Left Shunt

A

PaO2 = Decreased
Inc to A-aO2 difference = yes (Increase, O2 volume in arterial is diluted)
FiO2 = No (mostly; PO2 doesn’t improve)

FiO2 = fraction of O2 in inspired air

93
Q

Hypoxemia: Effects on PaO2, increasing A-aO2 difference, FiO2 = 1.0

V/Q mismatch

A

PaO2 = Decreased
Inc to A-aO2 difference = yes (increased, not good match)
FiO2 = Increased

FiO2 = fraction of O2 in inspired air

94
Q

Hypoxemia: Effects on PaO2, increasing A-aO2 difference, FiO2 = 1.0

Diffusion Limitation

A

PaO2 = Decreased
Inc to A-aO2 difference = Yes (Increased, thickened)
FiO2 = Increased

FiO2 = fraction of O2 in inspired air

95
Q

In which of the following states would the oxygen content of alveoli (O2=100) resemble the trachea (O2 = 150, CO2=0)?
A. Emphysema
B. Pulmonary Fibrosis
C. Pulmonary Embolism
D. Foreign body obstruction distal to trachea
E. Exercise

A

Pulmonary Embolism

Clot blocks blood flow to lungs - no gas exchange

96
Q

Which of the following causes of arterial hypoxemia is NOT associated with an increase in the alveolar-arterial (A-a)O2 gradient?
A. V/Q mismatch
B/ Right-to-left shunts
C. Hypoventilation
D. Diffusion Limitation

A

Hypoventilation

2023 Systems Phys (41 decks)

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