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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
Blood flow and air distribution in lung | More flow where?
More flow at base
26
More ventilation where?
Base
27
Ventilation Perfusion Mismatch -
Ideal match when ratio is 1, typically is .8 throughout the lung though
28
At base there is more
Flow than ventilation | More flow and ventilation though compared to apex
29
At apex there is more
Ventilation than flow | But both still lower at apex compared to base
30
Arterial pressure inc from...
apex to base
31
Alveolar pressure inc from
equal at apex and base
32
Transmural pressure
Talking blood vessels now... | Inc from apex to base, inc capillary distension and dec resistance from apex to base
33
Burly Alveoli
Get more ventilation than flow (apex)
34
Weakling Alveoli
More flow than ventilation (base)
35
Ventilation Perfusion Ratio
Mismatching of ventilation and blood flow is responsible for most defective gas exchange in pulmonary diseases
36
Global, at rest, ratio is...
0.8
37
Regional Differences - Apex
Too much ventilation for given blood flow (3) Lots of O2 in alveolus (favorable for bacteria) CO2 low in alveolus
38
Regional Differences - Base
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
When perfusion (blood flow) is greater than airflow - too much CO2
Base | Too much CO2 = Dilation of airway, decreases airway resistance, inc airflow
40
When perfusion (flow) is greater than airflow - too little O2
Constriction of blood vessels, Inc vascular resistance, dec blood flow
41
When ventilation is greater then flow - Too little CO2
Bronchoconstriction --> Inc airway resistance, Dec airflow
42
When ventilation is greater than flow - too much O2
Vasodilation --> dec vascular resis --> inc blood flow
43
Zone 1
More ventilation than flow Alveolar presure is higher than arterial or venous press No blood flow through here - dead space nonexistent in healthy
44
Zone 2
alveolar is higher than venous but lower than arterial | Alveolar press is determining how much flow is going through
45
Zone 3
More blood flow than ventilation Arterial and venous are higher than alveolar Amount of flow depends on diff btw art and venous
46
Anatomical Dead Space
wasted air 150mL happens normally
47
Alveolar Dead Space
Ventilation to alveolus but no flow to meet it | wasted air
48
Venous admixture
Wasted blood | Have blood coming in, but no air to diffuse into, getting less oxygen in
49
More likely to get dead space
Apex
50
More likely to get venous admixture
Base
51
Dead Space
Anatomic + Alveolar Anatomic = air remaining in conducting zone Alveolar = alveoli that don't participate in gas exchange
52
Embolism
Air coming into alveoli but no flow to meet it so now you have inc. alveolar dead space
53
Embolism Compensation
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
What happens to CO2 with embolist
CO2 gets mroe diluted, end title CO2 dec.
55
Causes of alveolar dead space
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
Causes of venous admixture
1. Anatomical shunts | 2. Low regional ventilation perfusion ratio
57
Anatomical Shunts
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
Low regional ventilation perfusion ratio
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
Physiological Shunt
Total amount of wasted blood = venous admixture = anatomic shunt + low perfusion ratio Normally 1-2% of cardiac output (higher with COPD)
60
Bronchial Circulation
Suplies blood to conducting airways and supportin tissues | Capable of angiogenesis (new vessel formation)
61
Routes for bronchial circulation
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
Pulmonary Embolus
Dead Space | Wasted Air
63
Normal Apex Ratio
High V/Q | Burly Alveoli
64
Normal Base Ratio
Low V/Q Weakling Alveoli Limiting factor is ventilation
65
Airway Obstruction
Shunt Ratio = 0 Wasted Blood/Venous Admixture - flow but no air to meet it
66
Pulmonary Embolism - what is it
Inc in alveolar dead space | Most commonly caused by thrombi from a leg or pelvic vein
67
Pulmonary Embolism - Clinical Picture
Severe respiratory distress - chest pain Right ventricular failure Hypoxemia Hypotension
68
What is hypoxemia in pulmonary embolism caused by
Right to left shunting in areas of partial or complete atelectasis
69
What is the low BP in pulmonary embolidm caused by
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
Interalveolar Connection
Pores of Kohn
71
Pores of Kohn
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
Hydrostatic Pressure
Promotes fluid loss from capillaries | Fluid moves from capillaries into the interstitial space (edema)
73
Alveolar Surface Tension
Inward pressure on alveoli favors fluid loss from capillaries Fluid moves from capillaries into interstitial space
74
Colloid Osmotic Pressure
Created by plasma proteins - inhibits fluid leakage from capillaries From space into capillaries
75
Alveolar Pressure
Compresses interstiium and increases interstital pressure | From space into capillaries
76
Pulmonary Edema
Small net fluid efflux from pulmonary capillaries to interstitium - lymphatics picks up the excess fluid Excess fluid accumulation in interstitium is pulm edema
77
Causes of pulmonary edema
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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