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CP Exam 1 > Lecture 8: Pulmonary Blood Flow > Flashcards

Lecture 8: Pulmonary Blood Flow Flashcards

1
Q

Alveolar capillaries

A

The alveolar capillaries receive deoxygenated blood (low O2 and high CO2) from the right ventricle.

O2 and CO2 are exchanged between the blood and the air.

Millions of alveolar capillaries make it so that the alveoli are a sheet of capillaries.

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2
Q

Extra-alveolar capillaries

A

Extra-alveolar capillaries receive oxygenated (high O2, low CO2) blood from the left ventricle and deliver it to the lung tissue.

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3
Q

How do the extra-alveolar capillaries return to the heart?

A

They return to the heart in pulmonary veins (venous admixture).

This, reduces the the PaO2 of the arterial blood by a few mmHg and increases the PaCO2 to a small degree.

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4
Q

Alveolar capillary

PaO2 in artery

PaCO2 in artery

A

PaO2 in artery- low

PaCO2 in artery- high

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5
Q

Fx of alveolar capillary

A

Gas exchange in the alveoli

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6
Q

Alveolar capillary

Blood gas in the vein

A

High PaO2

Low PaCO2

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7
Q

Extra-alveolar capillary

PaO2 in artery

PaCO2 in artery

A

PaO2 in artery- high

PaCO2 in artery- low

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8
Q

Fx of the extra-alveolar capillary

A

Provide nutrients to and remove wastes from the airways

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9
Q

Extra-alveolar capillary

Blood gas in the vein

A

low PaO2

High PaCO2

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10
Q

What is venous adventure?

A

When venous blood is being dumped into arterialized blood.

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11
Q

What is pulmonary vascular resistance?

A

How hard it is to pump blood to the body.

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12
Q

What is the equation for blood pressure?

A

BP= CO * TPR

Blood pressure= cardiac output * total peripheral resistance (how hard it is to pump blood into the body)

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13
Q

How can we find out the pulmonary blood pressure?

A

PBP= CO * PVR

Pulmonary blood pressure = cardiac output * pulmonary vascular resistance

PVR= how hard it is to pump blood through the lungs.

CO at rest is 5L/minute

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14
Q

How will vascoconstriction affect the pulmonary vascular resistance/resistance to blood flow?

A

It will increase TPR.

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15
Q

What is our normal pulmonary blood pressure?

CO?

Pulmonary BP compared to systemic BP?

A

25/15 mm Hg

5L/min

PBP is really low.

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16
Q

What is our systemic BP?

Cardiac output?

BP?

A
  • 120/80 mmHg
  • 5 L/min
  • higher, compared to pulmonary BP.
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17
Q

The pulmonary vascular resistance is much ______ that we see in the rest of the body.

A

LOWER.

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18
Q

What determines our pulmonary vascular resistance?

A

It is so low because:

1. A high amount of capillaries

2. How many of those capillaries are open at any given time.

3. There is less sympathetic/vasoconstricting going to the lungs.

4. Lung volume

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19
Q

During excercise, how does our PVR change?

A

Our PVR will drop, because we will open more pulmonary capillaries to accommodate the increased cardiac output (CO).

PVR drops, CO increases.

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20
Q

At low or very high lung volumes, how will the pulmonary vascular resistance change?

A

The pulmonary vascular resistance will increase a little because as the tissue is stretched, it compresses the capillaries.

Ex. Just like a rubber band gets thinner when it is stretched, the diameter of the capillary will decrease a little, increasing the resistance.

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21
Q

Pulmonary vascular resistance

Normal value:

BP:

Blood volume:

A

Normal value: Low

BP: Low

Blood volume: 5L/min

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22
Q

Systemic resistance

Normal value:

BP:

Blood volume:

A

Normal value: Moderate

BP: Higher

Blood volume: 5L/min

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23
Q

What happens when you walk a lot and then lock your knees?

A

Gravity will act on the blood and pull it to the legs. When you lock your knees, it prevents the blood from going back up to the heart and brain.

Not locking the knees will allow the skeletal muscles to increase blood flow from his legs–> thorax.

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24
Q

How do gravity and blood work together?

A

Gravity works on blood. When we stand, the blood pressure in our legs increases compared to thhe heart or brain.

This is why whenever we stand on our head, we get a rush of blood there.

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25
Q

Describe the regional blood flow in the heart at zone 1, zone 2 and zone 3.

A

Zone 1 is the apex. Here, the lung is above the level of the heart.

  • BP is reduced
  • Blood flow is less
  • Alveoli are somewhat expanded

PA >Pa>PV

Zone 2- middle of the lung, at the level of the heart.

  • BP is a little higher.
  • Alveoli are average size.
  • Blood flow is normal.

Pa>PA>PV

Zone 3- base of the lung

  • BP is high because we are below the level of the heart
  • alveoli are smaller
  • Blood flor is greater
  • Pa>PV>PA
26
Q

Describe the distribtuoin of blood flow in the lung of an upright person, contrasting the pressures involved in creating the differences in blood flow.

A

The regional blood flow is determined by how gravity is acting on the blood and how much air is in that region.

Apex- high alveolar pressure, low BP, little blood

Middle region- normal pressure on both sides, normal blood

Base- relatively low alveolar pressure, relatively high BP and lots of blood

27
Q

What does NO (nitric oxide) do?

A

NO relaxes the smooth muscle by causing vasodilation.

It is made by the endothelium.

Important in normal pulmonary blood flow.

28
Q

What does endothelin-1 do?

A

Made in the lungs and is a vasoconstrictor.

It is a player in pathologic conditions, not normal.

29
Q

Thromboxane-A2

A

Same as endothelin-1.

It is found in the pulmonary vasculature.

30
Q

What is the STRONGEST modifier of pulmonary blood flow?

A

Oxygen.

31
Q

-Increase O2 causes

A

blood vessels relax because you want more blood flow.

32
Q

Decrease in O2 causes–>

A

vasoconstriction–> hypoxic vasconstriction–> increase in PVR–> blood will shunt where the O2 is.

33
Q

What would happen if our whole lung would vascoconstrict?

A

A decrease in O2 overall would cause our whole lung to vasoconstrict

–> increase PVR

–> increase in pulmonary BP

–> right heart failure will leave to right ventricle hypertrophy and periphery edema

34
Q

What helps us to prevent pulmonary edema?

A

KEEPING THE ALVEOLI DRY

35
Q

What is the job of alveoli?

A

Alveoli allow oxygen to move from the air–> blood.

However, O2 is not water soluble and the tissue is.

How do we move O2 across the barrier then? If the capillaries leaked their fluid into the alveoli, it would impair the ability of O2 to cross into the blood.

36
Q

What determines whether water moves from the capillaries–> alveoli?

A

STERLING FORCES control how much fluid moves from the capillaries –> lungs.

37
Q

What are the starling forces?

A
  1. Two hydrostatic pressures
    - Capillary hydrostatic pressure (Pc)- blood pressure in the capillary trying to push fluid in the alveoli.
    - Tissue hydrostatic pressure (Pt)- pushes fluid from the tissue–> capillary
  2. Oncotic pressures
    - Capillary oncotic pressure (πc)- favors fluid into the capillary
    - Tissue oncotic pressure (πtissue)- favors water into the alveolus
38
Q

What is unique about the Sterline forces in the lungs?

A

Because the lung is always trying to collapse and the chest wall is always trying to spring away, it creates a negative intrapleural pressure.

This will ALSO, create a (-Ptissue).

This, this favors filtration of the fluid from the capillary –> alveolus.

39
Q

What forces favor filtration from the alveolar–> capillary?

A

Capillary oncotic pressure (πc)

40
Q

How do we decide the direction fluid will flow?

A

(Pc + πtissue + Ptissue) - (πc)

41
Q

In the lung, what is the single greatest force that decides the directtion

A

Capillary hydrostatic pressure Pc

42
Q

What is the net result of the starling forces in the lungs?

A

Favor net filtration of fluid from capillary –> alveoli.

43
Q

Filtration of fluid from the capillary–> alveoli is bad for gas exchange, right?

A

YES.

44
Q

What do we do to solve the problem of net filtration of fluid into our alveoli?

A

The LYMPHATICS SYSTEM BB

The lymphatics will move the tissue away from the lungs and allow gas exchange.

45
Q

Describe the key mechanism that alveoli are kept dry.

A

Interstitial hydrostatic pressure is believed to be negative and favors filtration of fluid from the capillary–> alveolus.

The net Starling forces are beleived to favor filtration from capillary–> alveolus.

HOWEVER. THIS IS BAD. So to keep the alveoli dry, the lymphatics remove the filtered fluid.

46
Q

Rening-angiotensin system pathway

A

[Angiotensinogen + renin, a enzyme added to the plasma by the liver] –> Angiotensin 1

Angiotensin 1–> Angiotensin 2 by ACE in the lungs.

ACE also INACTIVATES bradykinin, a vasodilator.

47
Q

What happens to 10-15% of people who are placed on ACE inhibitors?

A

ACE inhibitors decrease BP, but 10-15% develop a cough because of an accumulation of bradkinin.

48
Q

What particpates in the metabolism of the arachonic acid metabolites?

A

LUNGS

49
Q

What is the role of the lungs and the metabolism of arachidonic acid?

A

Lungs participate in the metabolism of arachidonic acid metabolites.

Leukotrienes and prostaglandins, thromboxane A2 are made by the immune system activation in the lungs.

Prostaglanding E2, F2alpha and leukotrienes are almost completely remved from the circulation in the lungs.

50
Q

What is the pressure in the L and R atria?

A

15/4 mmHg

51
Q

What is the pressure in the R ventricle?

A

25/0 mmHg

52
Q

What is the pressure in the L ventricle?

A

120/0

53
Q

What side of the heart pumps the most blood?

A

They both pump the SAME amount of blood.

54
Q

What part of the heart has the highest pressure?

A

Ventricles

55
Q

Systolic pressure of the L ventricle when the heart is contracting is _____.

Systolic pressure of the R ventricle when the heart is contracting is ______..

A

120

25

56
Q

Diastolic of the L and R ventricle?

A

0 for both.

However, the diastole is higher for the atria than the ventricles.

57
Q

CO of the L and R ventricle?

A

5L of blood/ minute

58
Q

What is the pressure in the aorta?

Pulmonary artery?

What side of the heart pumps blood easier?

A

120/80

25/15

Pulmonary side of the heart pumps blood easier.

59
Q

What happens in there is a increase in volume (backflow) of blood?

A

It will linger in the lungs.

60
Q

How does the low levels of O2 in the systemic circulation differ from low levels of O2 in the pulmonary circulation?

A

In the systemic circulation, low levels of O2 lead to vasodilation (increases blood flow).

In the pulmonary circulation, low levels of O2 will lead to vasoconstriction (decrease blood flow). This results in hypoxic vasoconstriction. This occurs because we want to shunt blood away from poorly ventilated areas and take it to MORE ventilated areas.

61
Q
A

CP Exam 1 (29 decks)

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