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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
# Define: Hypoxemia
Low O2 in blood -> triggers vasoconstriction | No dilation (Hypoxic vasoconstriction)
26
Why would we want to deliver blood to a region of lung that has low O2?
We want to match ventilation and perfusion
27
O2 influences..
Vascular Diameter
28
CO2 influences
Airway diameter
29
In an upright person, blood flow is highest...and lowest..
Highest near the base and lowest near the apex | gravitational effect contributes to uneve distribution of BF
30
When leaving the pulmonary artery, blood must...
travel up to the apex | Every 1 cm above heart, hydrostatic pressure in the arterials dropos ## Footnote gravity effects blood flow in the veins too
31
Regional distribution of blood flow in the lungs is due to:
Effects of gravity on hydrostatic pressure Influence of alveolar pressure on alveolar vessels | Lungs divided into 3 zones based on pressure affects on capillaries
32
# Pressures affecting pulmonary blood flow Zone 1 | What is it? Characteristics , occurance, etc.
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
33
# Pressures affecting pulmonary blood flow Zone 2 | What is it? What happens here?
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
34
# Pressures affecting pulmonary blood flow Zone 3 | What is it? What occurs here?
Pa > Pv > PA Optimal gas exchange; V/Q = 0.8-1.0 | Normal Pressure
35
# Define Bulk Flow | What is it? What causes it? When does it occur?
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
36
# Define Diffusion | What is it? Why?
How gas moves in us from air -> liquid; liquid -> air gases moving due to their individual pressure gradients
37
What 2 factors determine gas diffusion?
Diffusion properties of membrane (Fick's Law) Pulmonary Capillary Blood Flow | Fick's law- Vgas = [AxDx(P1-P2)]/T
38
# Fick's Law of Diffusion Diffusion of a gas across a sheet of tissue is dependent on:
Partial Presure Gradients (ΔP) Surface area of membrane (A) Thickness of membrane (T) Diffusion constant (D) - solubility of gas/MW
39
# Fick's Law of Diffusion According to Fick's Law, kwhat is the major determinant of rate of diffusion of a gas?
Partial Pressure gradients (ΔP)
40
# Fick's Law of Diffusion Rate of diffusion increases, as partial pressure...
increases
41
# Fick's Law of Diffusion Rate of Diffusion increases, as surface area...
Increases
42
# Fick's Law of Diffusion Rate of Diffusion increases, as thickness...
Decreases | Increase thickness, decrease rate
43
# Fick's Law of Diffusion Rate of diffusion increases, as the diffusion constant...
Increases
44
# Fick's Law of Diffusion What might cause thickness of the membrane to increase?
Edema Pneumonia Fibrosis
45
O2 is found in the blood in what two forms?
Physically dissolved Bound to Hemoglobin (Hb)
46
# Transport of O2 in Blood Physically Dissolved
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
# Transport of O2 in Blood Bound to Hemoglobin (Hb)
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
What does Blood PO2 measure?
The portion of O2 dissolved in the blood | It is not a measure of total O2 content in blood
49
# Transport of O2 in Blood Oxyhemoglobin
Hb with bound oxygen can have up to 4 O2 on 1 Hb -> saturated | bright red
50
# Transport of O2 in Blood What is the importance of Saturated Hb?
It is relatively unstable and easily releases O2 in regions where the PO2 is low
51
# Transport of O2 in Blood Deoxyhemoglobin
Non-O2 bound Hb | Deep maroon
52
The amount of HbO2 is a function of
PO2 in blood
53
When blood PO2 is high, what happens to Hb?
Form HbO2 (increased % saturation)
54
When blood PO2 is low, what happens to Hb?
O2 is released from Hb | Decreased % saturation
55
The PO2 is the primary factor determining...
the % Hb saturation
56
# Define SO2
% saturation of Hb with O2 (O2 actually bound to Hb/Potentially bound to Hb) x 100
57
What effect does O2 binding have on Hb?
Binding of O2 to each heme group increases affinity of the Hb to bind additional O2
58
# What is it? The Oxyhemoglobin Dissociation Curve
How plasma PO2 affects O2 loading and unloading from Hb
59
What does P50 mean?
Hb is 50% saturated
60
# Advantages of S shaped curved: Plateau
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% ## Footnote Large range of PO2 Hb can still be loaded
61
# Advantages of S shaped curved: Steep
Gives up large amounts of O2 in tissues | Small change in PO2 that leads to large drop in HbO2
62
Hb results in a large net transfer of O2 by...
Keeping PO2 low
63
Blood PO2 depends only on....
Concentration of dissolved O2
64
Hb acts as a...
storage depot for O2
65
How does Hb interact with O2? | Why is it important?
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
# Oxyhemoglobin Dissociation Curve A shift in either direction has the greatest effect on which phase?
Steep
67
# Oxyhemoglobin Dissociation Curve Right Shift ##Footnote What effect does it have to HbO2 binding? What does it do?
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
What factors besides PO2 can shift the oxyhemoglobin dissociation curve?
CO2 Acidity 2,3 diphosphoglycerate Exercise Temperature | CADET face right -> factors shift curve right
69
Why is CO so dangerous to us?
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
What 3 ways is CO2 transported in the blood?
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
What tells us how much O2 is in the blood?
CaO2 | To answer "how much" need to know how much O2 bound to Hb ## Footnote CaO2 - total O2 content in blood; given by SaO2 and Hb content
72
What does PaO2 tell you?
O2 molecules dissolved in plasma adequacy of gas exchange within the lungs when it is subtracted from calculated PAO2
73
What does SaO2 tell you?
Heme sites occupied by O2 (saturated) The % of all the available heme binding sites saturatrd with O2 Mainly determined by PaO2
74
What does CaO2 tell you?
Directly reflects the totaly number of O2 in arterial blood (bound and unbound) incorporates Hb content | Calculate by oxygen content equation
75
PaO2 is determined by...
PAO2 and the state of alveolar capillary membrane (not by amount of Hb available to soak up)
76
PaO2 determines...
the O2 saturation of Hb
77
What determines the total amount of O2 in blood or CaO2?
The SaO2, the concentration of Hb, and PaO2
78
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?
PaO2 unchanged, SaO2 unchanged, CaO2 reduced (half)
79
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: PaO2 85 mmHg., 85% SaO2, 95% Hb 7 gm%
80
APEX Summary
Decreased Blood flow Decreased ventilation Increased V/Q ratio PaO2 PaCo2
81
Base Summary
Increased blood flow (over perfused) Increased ventilation Decreased V/Q ratio Decreases PaO2 (blood not fully oxygenated) Increases PaCO2
82
The functional importance of V/Q ratios is...
Matching regional ventilation to blood flow
83
Alveolar (A) - arterial (a) difference in PO2
Measure of gas exchange efficiency across alveolar-capillary membrane | PAO2 - Calculated, PaO2 - measured
84
Normal P(A-a)O2: < 20 mmHg. What causes this?
Normal V/Q mismatch Return of bronchial and coronary blood (deoxygenated) through the thesbian veins to the left side of her heart
85
_ helps determine cause of hypoxia
A-a O2 gradient
86
What are the 5 causes of Hypoxemia?
Hypoventilation Low inspired O2 Right-to-left-shunt V/Q mismatch Diffusion impairment
87
Hypoventilation
Not ventilating well
88
When would you have low inspired O2, resulting in low PO2.
High altitude
89
How does the right-to-left shunt work?
Send deoxygenated blood into oxygenated
90
# Hypoxemia: Effects on PaO2, increasing A-aO2 difference, FiO2 = 1.0 Hypoventilation
PaO2 = decreased Inc to A-aO2 difference = no (unchanged) FiO2 = Increased | FiO2 = fraction of O2 in inspired air
91
# Hypoxemia: Effects on PaO2, increasing A-aO2 difference, FiO2 = 1.0 Low PIO2
PaO2 = decreased Inc to A-aO2 difference = no (diffusion unchanged) FiO2 = Increased | FiO2 = fraction of O2 in inspired air
92
# Hypoxemia: Effects on PaO2, increasing A-aO2 difference, FiO2 = 1.0 Right-to-Left Shunt
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
# Hypoxemia: Effects on PaO2, increasing A-aO2 difference, FiO2 = 1.0 V/Q mismatch
PaO2 = Decreased Inc to A-aO2 difference = yes (increased, not good match) FiO2 = Increased | FiO2 = fraction of O2 in inspired air
94
# Hypoxemia: Effects on PaO2, increasing A-aO2 difference, FiO2 = 1.0 Diffusion Limitation
PaO2 = Decreased Inc to A-aO2 difference = Yes (Increased, thickened) FiO2 = Increased | FiO2 = fraction of O2 in inspired air
95
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
Pulmonary Embolism | Clot blocks blood flow to lungs - no gas exchange
96
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
Hypoventilation

2023 Systems Phys (41 decks)

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