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Respiratory > Week 3 Pulmonary & Bronchial Circulations > Flashcards

Week 3 Pulmonary & Bronchial Circulations Flashcards

1
Q

What equals the right ventricular ejection fraction?

A

LV cardiac output

*left cardiac output = right cardiac output

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2
Q

What does the pulmonary vessels divide into?

A

Alveolar

  • big capillary bed where gas exchange occurs
  • high pressure during lung expansion collapses alveolar vessels

Extra-alveolar

  • area the arteries and veins that covey blood to any front the conducting airways (tissues that don’t participate in gas exchange.
  • larger vessels
  • not affected by pressures in the lung
  • surrounding lung tissue pulls vessels open during large volume increases
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3
Q

What happens to pulmonary vascular resistance when you inhale?

A

It increases

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4
Q

What vessels provide longitudinal resistance to flow?

A

*alveolar vessels

  • not regulated by autonomic or hormone control
  • alveolar capillary walls contribute to 40% of total resistance
  • alveolar arterioles contribute to 50% of resistance
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5
Q

What reduces capillary resistance?

A
  • low lung volumes

- high blood flow rates

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6
Q

What increases capillary resistance?

A

-low BP or less vascular distending pressures

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7
Q

What is capillary resistance dependent on?

A

Lung conditions

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8
Q

How does CO affect blood flow through capillaries?

A

Passive regulation of blood flow through capillaries occurs in response to changes in CO

  • increased blood flow accommodated by recruitment and distinction
  • prevent rise in pulmonary driving pressure with increase in blood flow
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9
Q

How does BP affect pulmonary vascular resistance?

A

As you increase vascular pressure, pulmonary vascular resistance will decrease.

*Bc of recruitment and distinction. Increased flow opens other channels that are closed and distended open channels

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10
Q

What is pulmonary wedge pressure a good indicator of what?

A

Preload on left side of heart

Pulmonary artery diastolic pressure is usually close to wedge pressure. An estimable of the filling pressure of the left side of the heart

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11
Q

Capillary volume closely equals what?

A

Stroke volume.

Usually 70mL at rest or 1mL/kg of body weight
-with each heartbeat will replace all blood in capillary bed

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12
Q

What is the total blood volume from main pulmonary arter to left atrium?

A

500mL

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13
Q

What is the blood distribution between artery and vein in pulmonary circulation?

A

It’s equally distributed between arteries and veins

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14
Q

What is function of the capacitance reservoir for the left atrium?

A

Pulmonary vasculature acts as a reservoir and cal alter its volume from 50% to 200% of resting volume.

  • prevents changes in blood return to left ventricle from affecting left ventricular diastolic filling over 2-3 cardiac cycles.
  • a buffer. Helps your body compensate for any abrupt changes in position
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15
Q

What are ways that capillary volume can be increased?

A
  • Recruitment

- Distention

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16
Q

What is the main process that causes pulmonary vascular resistance to go down?

A

*Recruitment

  • increases capillary volume by opening closed vessels
  • increased CO raises pulmonary vascular pressure, but decreases pulmonary vascular resistance
  • occurs during periods of stress and increased tissue oxygen demand
  • chief mechanism for fall in PVR
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17
Q

What is distention?

A

-Internal vessel pressure raise and open capillary beds

  • If goes on too long a can lead to…..
  • elevated left atrial pressure distends capillary beds (mitral regurgitation, LV failure)
  • lead to lung congestion and heart failure
  • mechanism seen at high vascular pressures
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18
Q

How does inspiration affect pulmonary blood flow?

A
  • pleural pressure more negative
  • pressure gradient for blood flow in thorax is increased
  • RV receives greater blood volume during diastole
  • increase in venous return into thorax
  • LV ejects less blood secondary to increased pressure gradient between LV and systemic pressures
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19
Q

How does exhalation affect pulmonary blood flow?

A
  • pleural pressure less negative
  • more positive thoracic pressure decreases venous blood return
  • decreases pressure gradient, prevents venous return to RV
  • less RV ejection pressure
  • the reduced gradient between LV and systemic arteries allows increased stroke volume

don’t worry too much about

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20
Q

What happens to PVR when lung volume is close to FRC?

A

PVR is minimal

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21
Q

What happens to PVR with higher and lower lung volumes?

A

PVR is increased

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22
Q

What happens to extra-alveolar vessels during inspiration?

A
  • They dilate and reduce flow resistance

- They receive increased lung volume as higher alveolar pressure compresses alveolar vessels

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23
Q

What happens to alveolar vessels during inspiration?

A

They compress

  • capillary resistance increased during elevated alveolar pressures
  • pulmonary capillaries are vessels of major vascular resistance
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24
Q

What are the effects of mechanical ventilation on pulmonary venous pressure?

A
  • alveolar pressure artificially increased
  • increases the amount of ZONE 2 lung volume relative to pulmonary venous pressure
  • the rise in alveolar pressure increases resistance to blood flow in ZONE 2
  • can decrease CO or increase V/Q imbalance or mismatch
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25
Q

Oxygenated blood from the aorta nourishes what lung structures?

A
  • conducting airways to terminal bronchioles
  • parenchyma supporting structures
    • pleura, interlobar septal tissues, pulmonary arteries and veins
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26
Q

What is the pressure of bronchial blood flow?

A

Systemic pressure

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27
Q

How much of bronchial circulation returns to the right atrium via the azygos vein?

A

50%

28
Q

What are some of the functions fo the pulmonary lymphatic system?

A
  • critical to keep alveoli free of fluid moving from capillaries
  • hydrostatic starling forces tent to move fluid out at 20mL/hr
  • Numerous lymphatic drain fluid from interstitium which is kept at a slight negative pressure
  • alveolar edema interferes with pulmonary gas exchange
29
Q

What is the Fick Principle?

A

One method of determining CO, blood flow through lungs/min

30
Q

What is the indicator dilution principle?

A

Dye injected into venous circulation

Diluted concentration measured on arterial side

31
Q

What is gravity’s effects on systemic blood pressure?

A
  • degree of pressure change from level of the heart
  • pressure gradient of 0.74mmhg/cm
  • in supine position, arterial pressure higher in feet than head
32
Q

What is the effects of gravity of pulmonary circulation?

A
  • Greater alterations in flow occur bc pulmonary circulation pressures much lower
  • distribution of blood flow in the lungs affected by gravity (in upright lung)
  • changes in pulmonary arterial pressure affect distribution of blood flow over the height of the lung
33
Q

What is hydrostatic pressure?

A
  • the pressure effect gravity has on a column of fluid
  • alters the potential energy of fluid in a column.
  • gravity affects the perfusion of blood in the different zones of the lung.
34
Q

What is considered the zero reference point for hydrostatic pressure

A

Right atrium level and middle of lung

35
Q

What portion of the lung receives more blood flow?

A

The lung base receives a greater portion of RV ejection fraction than apex of the lung

36
Q

What is PA?

A

Alveolar pressure

Arteriole sac

Highest at apex of the lung. Will close off small capillaries in ZONE 1, no gas exchange taking place

37
Q

What is Pa?

A

Pulmonary Artery pressure

De-oxygenated blood coming into the lung

38
Q

What is Pv?

A

Pulmonary Venous pressure

-oxygenated blood going out to tissues

39
Q

Describe the difference zones of the lung

A
  • ZONE 1
  • does not receive blood flow. (PA>Pa)
  • pulmonary capillaries collapse by higher PA
  • high V/Q mismatch
  • ZONE 2
  • intermittent blood flow. Blood flow with systole bc at that point Pa>PA
  • some gas exchange occurring
  • ZONE 3
  • most ideal
  • Pa>Pv>PA
  • blood vessel stays open entire time
  • ZONE 4
  • an abnormal condition of reduced blood flow

**ventilation increases as you go down the lungs and increased blood flow

40
Q

The perfusion of the lung zones depends on what?

A

-the relationship between alveoli and blood pressure in pulmonary arteries and veins

41
Q

What affects the perfusion distribution in the lung?

A
  • gravity affects the regional distribution of blood flow in different lung zones
  • transmutation distending pressure of vessels at bottom of lung > apex
  • alveoli pressure affects blood flow
  • pulmonary, arterial, venous, and alveolar pressure difference create lung zones
42
Q

What factors expand ZONE 1?

A
  • decreased pulmonary artery pressure
    • shock, hypovolemia
  • increased alveolar pressure
    • PEEP
  • occlusion of blood vessels
    • PE
43
Q

What factors reduce ZONE 1?

A
  • increased pulmonary artery pressure
    • infusion of fluid or blood
  • reduced hydrostatic effect
    • change pt position
    • standing to supine
44
Q

What is the pulmonary-hemodynamic curve?

A

-assessment of driving pressures across the pulmonary vasculature as CO varies

45
Q

How does pulmonary vascular resistance change blood flow?

A
  • active regulation occurs by altering vascular smooth muscle tone in pulmonary vessels (arterioles)
  • pulmonary capillary smooth muscle alters PVR
  • vasomotor tone of pulmonary vessels is affected by may factors
46
Q

What is the most active regulator of pulmonary vessels?

A

Regulation is primary regulated by local metabolic influences

47
Q

What causes vasoconstriction of pulmonary vessels?

A
  • reduced PAO2*
  • increased PCO2*
  • histamine*
48
Q

What causes vasodilation of pulmonary vessels?

A

-increased PAO2*
-nitric oxide*
-

49
Q

What is Thromboxane A2

A
  • a potent vasoconstrictor
  • constrictor of pulmonary arterial and venous smooth muscle
  • will send blood elsewhere other than damaged area of lung where gas exchange can occur
50
Q

What is Prostacyclin (Prostaglandin 12)?

A
  • potent vasodilator

- produced by endothelial cells

51
Q

What does nitric oxide do to epithelium?

A
  • potent endothelium-derived endogenous vasodilator
    • strictly localized effect
    • leads to smooth muscle relaxation through synthesis of cyclic GMP
  • can be toxic in high concentrations and binds irreversibly to heme iron in hemoglobin
52
Q

What are the effects of alveolar oxygen tension on pulmonary blood flow?

A
  • partial pressure of oxygen (PAO2) in alveoli is a critical governing pulmonary circulation
  • PO2 in alveoli more important than oxygen tension in mixed venous blood
  • oxygen diffusion into pulmonary arteriole walls causes smooth muscle dilation
    • as alveolar oxygen tension decreases, surrounding arterioles constrict.
    • will shunt areas of blood award from places getting not ventilation well (like mucous plug). Sense low O2 and shunt blood to areas venting better
  • global reduction in alveolar oxygen tension increases total PVR by constricting arterioles and small arteries
53
Q

What does alveolar hypoxia produce?

A

Hypoxic pulmonary vasoconstriction(HPV)

  • localized response
  • response enhanced if high CO2
  • opposite reaction than systemic circulation hypoxia
    • systemic blood vessels dilate in response to hypoxia
  • HPV is an important mechanism of balancing V/Q ratio.
    • shift of flow to better ventilated pulmonary regions
54
Q

What is pulmonary HTN?

A

-increased resistance to blood flow in the lung
-high pulmonary vascular resistance, elevated pulmonary artery pressures.
Can be seen with:
-generalized alveolar hypoxia (COPD)
-hypoventilation
-low inspired PO2
-increased PCO2
-pain
-histamine release

*can increase work of right ventricle

55
Q

What is primary pulmonary HTN?

A

*serious pulmonary vascular condition

  • small muscular pulmonary arteries narrow
  • very high pulmonary artery pressures
  • RV pressure increases to compensate until RV failure
  • lung transplant is only effective treatment
56
Q

Is ventilation evenly distributed throughout lung?

A

No

Lower portion of lung tends to be ventilated > than apex

57
Q

Is compliance greater at base or apex of the lung?

A

Greater at the base

58
Q

Why does the apex of the lung have a higher PO2?

A

Because it’s not getting perfused and oxygen isn’t being extracted

59
Q

What. Is a normal A-a gradient?

A

Alveolar to arterial parietal pressure gradient is normally 10-15 mmHg

Looks at how well O2 gets from alveolar space into the artery

-larger gradients indicate intrinsic pulmonary disease—>shunting

60
Q

What is a right to left shunt?

A

De-oxygenated Blood coming from right area of the heart and not participating in gas exchange

Will decrease partial pressure of O2

There are some small, normal shunts

61
Q

What is left to right heart shunt?

A

Pulmonary venous recirculation

  • portion of OC returns to right heart without flowing through the body
  • does not affect systemic arterial oxygen tension
  • oxygen tension in right heart is increased
62
Q

CaO2

A

Oxygen carry capacity

How much O2 is carried in the arterial blood

20mL/dL

63
Q

DO2

A

Oxygen delivery

How much oxygen is carried in the blood and how fast it is being delivered to the tissues

1000mL/min

64
Q

EO2

A

Oxygen extraction ratio

Hoe much O2 is extracted by the tissues

25% for whole body (individual tissue beds will vary)

65
Q

VO2

A

Oxygen consumption

How much oxygen is consumed by the tissues

250mL/min (at rest)

66
Q

CvO2

A

Venous oxygen content

How much O2 is carried in the venous blood

15mL/dL

Respiratory (4 decks)

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