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CRRAB II- Week 3 > Trachte: Blood Flow and Metabolism > Flashcards

Trachte: Blood Flow and Metabolism Flashcards

1
Q

What does the pulmonary artery contain?

A

Mixed venous blood

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2
Q

What’s the PO2 in the pulmonary artery? PCO2?

A

PO2- 40

PCO2- 46

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3
Q

Describe the path of the pulmonary artery?

A

Branches w/ the airways down to the TERMINAL BRONCHIOLES.

Breaks into the PULMONARY CAPILLARIES for gas exchange.

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4
Q

What are pressures in the pulmonary capillaries normally?

A

Usually LOW–little resistance so the heart doesn’t have to work hard to perfuse lungs

25/8 mmHg

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5
Q

What conditions significantly alter pressures in the pulmonary capillaries?

A

CHF
Mitral Valve stenosis

Blood isn’t being pumped adequately so pressure in pulmonary systems begin to rise–> pulmonary edema

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6
Q

What is the mean pressure in the pulmonary capillaries?

A

15 mmHg

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7
Q

What is CO?

A

5 L/min

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8
Q

What is Left atrial pressure?

A

5 mmHg

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9
Q

What’s the pulmonary resistance? How does this compare with systemic resistance?

A

***2 ml/mmHg

systemic is 98/5 which is about 10x higher

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10
Q

What pressures surround the pulmonary capillaries?

A

Alveolar pressure (surrounded by alveoli)

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11
Q

How does pressure around the pulmonary capillaries differ during exhalation and inhalation?

A

exhalation- couple mmHg

Inspiration- subatmospheric

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12
Q

What happens to pulmonary vessels during inspiration?

A

They’re PULLED OPEN

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13
Q

Are there any conditions that radically change the pressure surrounding the vessel?

A
    1. Tension pneumothorax–can shut down blood flow if pressure gets high enough
      1. Positive pressure ventilation–> above atm pressure
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14
Q

Why does pulmonary a. resistance DECREASE w/ an INCREASE in pulmonary a. pressure?

A
  1. RECRUITMENT of additional capillaries in conducting blood flow
  2. DISTENSION of capillaries conducting blood to allow for more blood flow
  3. EXPANSION of lungs reduces resistance
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15
Q

How can alveolar pressure increase resistance?

A

Alveolar pressure can COMPRESS vessels to INCREASE RESISTANCE if it is greater than capillary pressure

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16
Q

How NTs contract vessels to increase resistance?

A

NE
5HT
Histamine

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17
Q

What NTs relax pulmonary vessels to REDUCE resistance?

A

Ach
isoproterenol
prostacyclin–> PGI2 (inhibits platelet agg and causes dilation) prevents MI

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18
Q

What is the fick principle?

A

O2 consumption = CO (CAO2 – CVO2)

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19
Q

What is the equation for pulmonary blood flow?

A

Pulmonary blood flow= VO2/(CAO2 – CVO2)

20
Q

How can you measure concentration of O2 in the arterial blood?

A

Inject a dye

21
Q

Why is there more blood flow to the base of the lung usually than the apex?

22
Q

What are the 3 potential zones of perfusion?

A
  1. Zone 1 : PA > Part > Pvenous
  2. Zone 2: Part > PA > Pvenous
  3. Zone 3: Part > Pvenous > PA
23
Q

What are the characteristics of Zone 1?

A

PA > Part > Pvenous

  1. NO FLOW occurs in this region
  2. This does not occur naturally but can occur in HEMORRHAGE OR POSITIVE BREATHING PRESSURE
  3. NO GAS EXCHANGE
24
Q

What is zone one referred to as? Where is it most likely to occur?

A

alveolar dead space

APEX of the lung

25
What does zone 2 represent? What determines blood flow in this region? Does venous pressure influence flow?
Part > PA > Pvenous PRESSURE DIFFERENTIAL between arteries and Alveoli Venous pressure DOES NOT influence flow
26
Where is zone 2 most likely to occur?
APICAL REGION of lung where pressures are the lowest
27
What does zone 3 represent?
Part > Pvenous > PA
28
What is flow in zone 3 dependent on? Where does it occur?
Arterial/venous pressure difference (normal for the circulatory system) MIDREGIONS or BASE of lugns
29
What happens during alveolar hpyoxia? What is this mechanism independent of?
alveolar hypoxia CONSTRICTS blood vessels perfusing the hypoxic region of the lung NERVES
30
What is the mechanism for alveolar hypoxia leading to constriction? What does this do to the membrane potential?
INHIBITION of voltage gated K channels--> more K stays inside cell> DEPOLARIZES cell/DECREASE MEMBRANE POTENTIAL> INCREASE in Ca leading to vasoconstriction
31
What controls fluid movement out of the pulmonary vasculature?
Starling foces
32
What is the formula for fluid escape?
Fluid escape = Kf (Pcap – P int) – ∂ (πcap – πint)
33
What are the constant values for fluid escape?
Capillary pressure is 15- interstitial pressure can vary Osmotic pressure is normally 25--> this should keep your lungs dry
34
Why is there a slight leak of fluid out of the lungs? How does this differ from systemic circulations?
Lymphatic drainage (20 ml/hr) MUCH LOWER in systemic circulations b/c of LOWER hydrostatic pressure
35
What are situations when fluid movement is increased?
Heart failure--> back up of fluid from heart into lung--> increased fluid in lungs--> SOB Not enough protein
36
What happens if too much fluid escapes from the lungs?
alveolar edema> SOB
37
What are other functions of the pulmonary circulation?
1. RESERVOIR for blood (we lay down blood drains from legs to lungs) 2. FILTER blood (thrombi in legs/periphery can't get to the brain)
38
What does the lung do to ang I?
Activates it to Ang II (mediated by ACE)
39
What does the lung do to bradykinin?
Inactivates it (mediated by ACE)
40
What affect does the lung have on 5HT levels?
Accumulates it and removes it from circulation--> 5HT is a vasoconstrictor
41
What does the lung synthesize?
both PGs and leukotrienes It can also REMOVE leukotrienes from circulation
42
What are PGS and leukotrienes?
Bronchoconstrictors
43
What is an important role of PGE in pulmonary/systemic circulation?
Keeps DA open in fetal circulation.
44
How do ACE inhibitors cause cough?
Prolong bradykinin actions--> COUGH
45
If you wished to treat a patent ductus arteriosus pharmacologically what would you use?
Indomethacin (COX inhibitor)

CRRAB II- Week 3 (12 decks)

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