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FS Exam 3 > Pulmonary Circulation > Flashcards

Pulmonary Circulation Flashcards

1
Q

Pulmonary Circulation

A

Largest vascular bed
Accommodates the entire cardiac output from the right heart
Rarely concerned with directing bloodflow

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2
Q

Bronchial Circulation

A

1-2% of cardiac output
Empties into pulmonary vein
Generates physiological shunt
With greater pathology –> greater amount is shunted (wasted volume)

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3
Q

Cardiac Output

A

Output of blood per minute
5L/min
R = to lungs
L = to body

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4
Q

In contrast to systemic circulation, in the lung….

A
  1. Rarely concerned with directing blood flow
  2. Much lower pressure
  3. Better clot filter
  4. Contains about 10% of total blood volume
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5
Q

Lower pressure in pulmonary circulation

A

Maintained by low resistance due to # of capillaries

Less smooth muscle than vessels in systemic circulation –> so changes diameter

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6
Q

Pulm. Circ. better clot filter

A

Can be bad with pulmonary embolism

Fibrinolytic substances are released from endothelium

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7
Q

Relationship btw. perfusion pressure and resistance unique in the lung

A

P = flow * resistance
Resistance is inversely related to diameter and pressure
As arterial pressure goes up, resistance goes down

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8
Q

As you increase cardiac output, what happens to flow, resistance and pressure

A

Increase flow
Increase pressure
Decrease resistance - alveoli are recruiting more capillaries and distend the ones that are already open

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9
Q

How does vascular resistance get so low?

A
  1. Recruitment

2. Distension

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10
Q

Recruitment

A

As you recruit more capillaries, pressure will drop
Fewer open capillaries at lung apex at rest
With increased CO2, the capillaries will open
As inc press, alveoli will recruit more and open up and keep resistance down

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11
Q

Distention

A

Inc CO2 stretches capillaries so they open more, pulmonary capillaries are thin and compliant

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12
Q

Benefits to vascular resistance being low

A

capillary recruitment and distension increase surface area for gas exchange
Decreases risk of pulmonary edema
- if had high pressure, there would be an inc in fluid leakage and edema

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13
Q

Resistance is affected by lung volume - inhalation

A 
Alveolar vessels (pul cap) are exposed to expanding alveoli and are compressed
Extraalveolar vessels are exposed to decreasing intrapleural pressure and expand
Inhale = inc resistance
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14
Q

Resistance is affected by lung volume - exhalation

A

apposite occurs

Decrease resistance

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15
Q

Lower resistance does what to work of the heart

A

lowers the work

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16
Q

Resistance is lowest when>

A

FRC

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17
Q

Resistance affected by chemical mediators

A

Unique response to oxygen

Hypoxic Pulmonary VC = dec in O2 tension, Inc in pulmonary vascular resistance

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18
Q

Regional Hypoxia

A

due to bronchial obstruction
Diverts blood away from poorly ventilated areas
Constrict area with bad gas exchange and distribute blood to areas where gas exchange can occur

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19
Q

Generalized Hypoxia

A

Altitude –> widespread inc in pulmonary vascular resistance and pressure –> might lead to pulmonary hypertension and right heart hypertrophy

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20
Q

NE

A

Vasoconstriction

Bronchodilation

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21
Q

Hypoxic Pulmonary Vasoconstriction

A

Controls pulmonary blood flow distribution to better ventilated areas –> main mechanism for explaining sustained pulmonary hypertension

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22
Q

Hypoxic Pulmonary Vasoconstriction triggered by,…

A
  1. Airway obstruction
  2. Acute lung damage (pneumonia)
  3. Altitude
  4. Diseases like COPD
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23
Q

Pulmonary Arterioles Dec O2 vs. Inc O2

A 
Dec = Vasoconstriction
Inc = Vasodilation
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24
Q

Systemic Arterioles Dec O2 vs Inc O2

A 
Dec = vasodilation
Inc = vasoconstriction
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25
Q

Blood flow and air distribution in lung

More flow where?

A

More flow at base

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26
Q

More ventilation where?

A

Base

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27
Q

Ventilation Perfusion Mismatch -

A

Ideal match when ratio is 1, typically is .8 throughout the lung though

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28
Q

At base there is more

A

Flow than ventilation

More flow and ventilation though compared to apex

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29
Q

At apex there is more

A

Ventilation than flow

But both still lower at apex compared to base

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30
Q

Arterial pressure inc from…

A

apex to base

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31
Q

Alveolar pressure inc from

A

equal at apex and base

32
Q

Transmural pressure

A

Talking blood vessels now…

Inc from apex to base, inc capillary distension and dec resistance from apex to base

33
Q

Burly Alveoli

A

Get more ventilation than flow (apex)

34
Q

Weakling Alveoli

A

More flow than ventilation (base)

35
Q

Ventilation Perfusion Ratio

A

Mismatching of ventilation and blood flow is responsible for most defective gas exchange in pulmonary diseases

36
Q

Global, at rest, ratio is…

A

0.8

37
Q

Regional Differences - Apex

A

Too much ventilation for given blood flow (3)
Lots of O2 in alveolus (favorable for bacteria)
CO2 low in alveolus

38
Q

Regional Differences - Base

A

Too much perfusion for the level of ventilation (0.6)
Some blood is not adequately oxygenated
Lower PO2 and higher PCO2 of blood leaving alveolar capillaries from here

39
Q

When perfusion (blood flow) is greater than airflow - too much CO2

A

Base

Too much CO2 = Dilation of airway, decreases airway resistance, inc airflow

40
Q

When perfusion (flow) is greater than airflow - too little O2

A

Constriction of blood vessels, Inc vascular resistance, dec blood flow

41
Q

When ventilation is greater then flow - Too little CO2

A

Bronchoconstriction –> Inc airway resistance, Dec airflow

42
Q

When ventilation is greater than flow - too much O2

A

Vasodilation –> dec vascular resis –> inc blood flow

43
Q

Zone 1

A

More ventilation than flow
Alveolar presure is higher than arterial or venous press
No blood flow through here - dead space
nonexistent in healthy

44
Q

Zone 2

A

alveolar is higher than venous but lower than arterial

Alveolar press is determining how much flow is going through

45
Q

Zone 3

A

More blood flow than ventilation
Arterial and venous are higher than alveolar
Amount of flow depends on diff btw art and venous

46
Q

Anatomical Dead Space

A

wasted air
150mL
happens normally

47
Q

Alveolar Dead Space

A

Ventilation to alveolus but no flow to meet it

wasted air

48
Q

Venous admixture

A

Wasted blood

Have blood coming in, but no air to diffuse into, getting less oxygen in

49
Q

More likely to get dead space

A

Apex

50
Q

More likely to get venous admixture

A

Base

51
Q

Dead Space

A

Anatomic + Alveolar
Anatomic = air remaining in conducting zone
Alveolar = alveoli that don’t participate in gas exchange

52
Q

Embolism

A

Air coming into alveoli but no flow to meet it so now you have inc. alveolar dead space

53
Q

Embolism Compensation

A

Vessels go through hypoxic vasoconstriction to redirect blood to areas of good ventilation so arterial press will inc and work load will inc too
Can lead to heart failure

54
Q

What happens to CO2 with embolist

A

CO2 gets mroe diluted, end title CO2 dec.

55
Q

Causes of alveolar dead space

A
  1. Hydrostatic Pressure Failure (gravity effect)
  2. Normal
  3. Emobolus
  4. Emphysema - destruction of walls and elastic tissue, more air going in that wont participate in gas exchange, destroys surface area
  5. Pre-capillary constriction
56
Q

Causes of venous admixture

A
  1. Anatomical shunts

2. Low regional ventilation perfusion ratio

57
Q

Anatomical Shunts

A

blood that doesn’t get to ventilated areas of the lung
Atrial of ventricular septal defect
Direct connection of pulmonary artery to vein
Some bronchial venous blood dumps directly into pulmonary veins (normal)

58
Q

Low regional ventilation perfusion ratio

A

Insufficient alveolar ventilation to adequately oxygenate blood in a region of the lung
Occurs at base of lung under normal conditions (weakling alveoli)
Partially restricted airway –> regional hypoventilation

59
Q

Physiological Shunt

A

Total amount of wasted blood = venous admixture = anatomic shunt + low perfusion ratio
Normally 1-2% of cardiac output (higher with COPD)

60
Q

Bronchial Circulation

A

Suplies blood to conducting airways and supportin tissues

Capable of angiogenesis (new vessel formation)

61
Q

Routes for bronchial circulation

A

Bronchial Veins - Carry about 50% of bronchial blood flow directly to atrium
Bronchopulmonary Anastomoses - Connect bronchial blood flow to pulmonary veins, Contributes to Venous Admixture

62
Q

Pulmonary Embolus

A

Dead Space

Wasted Air

63
Q

Normal Apex Ratio

A

High V/Q

Burly Alveoli

64
Q

Normal Base Ratio

A

Low V/Q
Weakling Alveoli
Limiting factor is ventilation

65
Q

Airway Obstruction

A

Shunt
Ratio = 0
Wasted Blood/Venous Admixture - flow but no air to meet it

66
Q

Pulmonary Embolism - what is it

A

Inc in alveolar dead space

Most commonly caused by thrombi from a leg or pelvic vein

67
Q

Pulmonary Embolism - Clinical Picture

A

Severe respiratory distress - chest pain
Right ventricular failure
Hypoxemia
Hypotension

68
Q

What is hypoxemia in pulmonary embolism caused by

A

Right to left shunting in areas of partial or complete atelectasis

69
Q

What is the low BP in pulmonary embolidm caused by

A

You are inc press upstream of your embolist so this will make your right heart work a lot
downstream from the clot though there is not as much flow so not as much going into the left side so the pressure goes down

70
Q

Interalveolar Connection

A

Pores of Kohn

71
Q

Pores of Kohn

A

Pores btw. adjacent alveoli
Functions as means of collateral ventilation
If lung is partially deflated, ventilation can occur to some extent through the pores

72
Q

Hydrostatic Pressure

A

Promotes fluid loss from capillaries

Fluid moves from capillaries into the interstitial space (edema)

73
Q

Alveolar Surface Tension

A

Inward pressure on alveoli favors fluid loss from capillaries
Fluid moves from capillaries into interstitial space

74
Q

Colloid Osmotic Pressure

A

Created by plasma proteins - inhibits fluid leakage from capillaries
From space into capillaries

75
Q

Alveolar Pressure

A

Compresses interstiium and increases interstital pressure

From space into capillaries

76
Q

Pulmonary Edema

A

Small net fluid efflux from pulmonary capillaries to interstitium
- lymphatics picks up the excess fluid
Excess fluid accumulation in interstitium is pulm edema

77
Q

Causes of pulmonary edema

A

Increased capillary hydrostatic pressure
Increased capillary permeability
Loss of surfactant –> inc surface tension –> dec interstitial press
Starvation –> Loss of plasma proteins –> dec in osmotic press

FS Exam 3 (10 decks)

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