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CRRAB II Week 5 > Blood Flow & Metabolism > Flashcards

Blood Flow & Metabolism Flashcards

1
Q

What does the Pulmonary artery contain?

A

Mixed venous blood!

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2
Q

What is the PO2 in the pulmonary artery?

A

About 40 mmHg

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3
Q

What is the PCO2 in the pulmonary artery?

A

About 46 mmHg

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4
Q

How is most CO2 transported?

A

As bicarbonate

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5
Q

How does the pulmonary circulation travel?

A

It branches with the airways down to the terminal bronchioles -> then breaks into pulmonary capillaries for gas exchange

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6
Q

What are the pressures in the pulmonary capillaries?

A

Relatively low (25/8 mmHg normally)

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7
Q

What conditions significantly alter the low pressure in the pulmonary capillaries?

A
  • Pulmonary HTN (when pressure goes up)
  • Heart failure –> elevated pulmonary artery pressures
  • Anything that causes inadequate pumping from the left of the heart
  • Alveolar hypoxia (COPD) patients all have pulmonary HTN
  • High altitudes –> cause pulmonary HTN
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8
Q

What is the mean pressure in the pulmonary circulation?

A

15 mmHg

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9
Q

What is the cardiac output?

A

5L/min

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10
Q

What is the left atrial pressure?

A

5 mmHg

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11
Q

What is the resistance in the pulmonary capillaries if the flow is 5L/min, mean arterial pressure is 15 mmHg and the pressure is 5mmHg in the left atrium?

A

Resistance = Change in P/Flow

=15-5 mmHg = 10 mmHg/5L/min = 2!!

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12
Q

What is the pressure around the pulmonary capillaries?

A

During exhalation = couple mmHg

During inhalation = subatmospheric

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13
Q

What is the pressure around pulmonary capillaries known as?

A

Surrounded by alveoli.

Therefore, it’s alveolar pressure.

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14
Q

What happens to pulmonary vessels during inspiration?

A

They are pulled open!

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15
Q

Why do people die from tension PTX?

A

It crushes the venis in the lungs!

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16
Q

IMP: Are there any conditions that radically change the pressure in around the pulmonary capillaries?

A

Tension PTX (very high tension —–> compress blood flow), anything that increases pressure in the chest

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17
Q

How does pulmonary artery resistance relate to pulmonary artery pressure ?

A

Resistance decreases with an increase in pulmonary artery pressure

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18
Q

What causes pulmonary artery resistance to decrease with an increase in pulmonary artery pressure?

A
  • Recruitment of additional capillaries in conducting blood flow
  • Distention of capillaries conducting blood to allow more blood to flow
  • Expansion of the lung also reduces resistance
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19
Q

What does alveolar pressure do if it is greater than capillary pressure??

A

It can compress vessels to increase resistance!

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20
Q

What does NE, Serotonin and Histamine do to vessels?

A

Contracts pulmonary vessels to reduce their resistance.

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21
Q

What does Acetylcholine (ACh), Isoproterenol & Prostacyclin do to pulmonary vessels?

A

Relaxes/dilates pulmonary vessels to reduce resistance

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22
Q

What does the shorter length of the pulmonary circulation cause?

A

Shorter length –> allows it to have lower pressure (mean = 15 mmHg) and lower resistance
-Ex: in the short artery traveling from the RV to the pulmonary circulation

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23
Q

What does the longer length of the systemic circulation cause?

A

-Longer length –> higher resistance, higher pressure (mean = 100 mmHg)
It also has muscular arteries

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24
Q

What is pulmonary resistance??

A

Delta P/Flow = 15-5 = 10 mmHg/5 L/min (CO) = 2 mmHg/L/min

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25
What does Fick's Principle Measure?
Oxygen consumption
26
What is Fick's Equation?
O2 consumption = Cardiac Output (CaO2 - CvO2) C = concentration of O2 -Referring to systemic arterial & venous blood here
27
How do we calculate pulmonary blood flow?
Pulmonary blood flow = VO2/ (CaO2-CvO2) | VO2 = oxygen consumption
28
If oxygen volume consumed is 250 ml/min (at rest) and oxygen concentration in blood is 20 ml/dL and 15 ml/dL in arteries and veins, what is pulmonary flow?
250/(20-15) = 250/5 = 50 dL = 5L
29
Let's say CO2 production is 200 mL/min and O2 consumption is 250 mL/min, what is the respiratory quotient?
200 mL/min / 250 mL/min = 0.8
30
What does a 0.8 respiratory quotient indicate?
You aren't producing as much CO2 as you're using O2 --> this means you're burning fat!
31
What happens to the respiratory quotient when you exercise?
The number increases to 1 because your CO2 production is similar to your O2 consumption
32
Where is there more blood flow in the lung?
More flow to the base of the lung than to the apex because of gravity
33
How many zones of perfusion exist?
Three!
34
What is the flow in zone 1 of perfusion? What are the pressures?
Palveolar > Parterial > Pvenous - No flow occurs in this region - This does not occur naturally but can occur in hemorrhage or positive pressure breathing - This area does not participate in gas exchange (physiologic dead space) - -> Most likely to occur at apex of lung
35
What influences the flow in zone 2 of perfusion? What are the pressures?
Parterial > Palveolar > Pvenous - Blood flow in this region is determined by pressure differential between arteries and Alveoli - Venous pressure does not influence flow - Most likely to occur in the apical region of the lung
36
What influences the flow in zone 3 of perfusion? What are the pressures?
Parterial > Pvenous > Palveolar - Flow is dependent on the arterial/venous pressure difference (i.e., normal situation in the circulatory system) - Occurs in the mid regions or base of lungs - Zone 3 is the "normal region"
37
What does alveolar hypoxia do the blood vessels perfusing the hypoxic region of the lung?
Alveolar hypoxia will CONSTRICT the hypoxic region of the lung (diverts the blood to other non-hypoxic areas)
38
How does alveolar hypoxia lead to blood vessel constriction in that area?
- Mechanism independent of nerves - Appears to involve inhibiting voltage gated K+ channels - -> this would hypopolarize (depolarize) the membrane potential - Causes an increase in [Ca] leading to a vasoconstriction
39
What are examples of when alveolar hypoxia and resultant blood vessel constriction occurs?
-High altitudes, newborns
40
What forces control fluid movement out of the pulmonary vasculature?
Starling forces
41
What is the equation that describes starling forces and the fluid movement in the lung?
Fluid escape = Kf (Pcap - Pint) - delta(picap - pi int)
42
What is the 'fluid escape' or flow in the lungs?
constant (15 - ?) - constant (25 - ?) = -10 = fluid reabsorption
43
Why is it good that fluid movement is shifted toward reabsorption in the lungs?
-It's good for keeping the lungs dry
44
What might leak out of the lungs? What does this cause?
- Must be a slight leak of fluid out the lungs because there is lymphatic drainage (20 ml/hr) - This is .001/.01% of total flow - This should be much less than in systemic circulations because of the lower hydrostatic pressure (Pcap)
45
How does oncotic and hydrostatic pressure change along the capillary
As the capillary moves from arteriole to venous the hydrostatic pressure drops and the oncotic pressure remains the same the whole time.
46
What are situations where fluid movement would be increased (fluid movement into the lungs)?
- Heart failure | - Pulmonary HTN
47
What does too much fluid in the lung cause? What do patient's experience?
Too much fluid escapes --> alveolar edema | -Experienced as shortness of breath
48
What are 25% of hospital admissions due to?
Heart failure
49
What are two functions of the lung relating to blood?
1. Reservoir for blood - -> When we lay down, blood drains from the legs to the lungs 2. Filter of blood - -> Thrombi in the legs (periphery) can not get to the brain (prevents PE from reaching brain and causing stroke!)
50
What does the lung activate?
Angiotensin I to Angiotensin II (but this occurs in all blood vessels) -Mediated by angiotensin converting enzyme
51
What does the lung inactivate?
Bradykinin | --> mediated by angiotensin converting enzyme (it breaks down bradykinin)
52
What does the lung accumulate?
Serotonin to remove it from the circulation
53
What does the lung metabolize?
Prostaglandin E1, E2 and F2alpha
54
What does the lung synthesize?
Prostaglandins & Leukotrienes (mediators of asthma) - -> bronchoconstrictors - Lung also removes leukotrienes from circulation
55
What is a very important function of PGE in the lung in early life?
Keeps the patent ductus arteriosus open
56
If you wished to treat a patent ductus arteriosus, what drug would be best?
Indomethacin (COX inhibitor)
57
How does indomethacin close the patent ductus arteriosus?
It inhibits COX which normally stimulates PGE and PGE dilates/causes the ductus arteriosus to remain patent.
58
Where is pressure lower, in the pulmonary or systemic circulation?
Pressure is MUCH LOWER in the pulmonary circulation
59
When does resistance fall in the pulmonary circulation?
Resistance is extremely low and falls further upon increases in cardiac output because of recruitment and distention
60
How is blood flow distributed?
Toward the base of the lung and away from the apex
61
How do you define Zone 1 of the lung?
-Physiological dead space | Paleveoli >Parteriole > Pvenous
62
How do you define Zone 2 of the lung?
Parteriole > Palveoli > Pvenous
63
How do you define Zone 3 of the lung?
Parteriole > Pvenous > Palveoli
64
What does poor ventilation do to blood flow?
Hypoxic pulmonary vasoconstriction reduces blood flow to poorly ventilated sections of the lung
65
What mediates fluid movement out of pulmonary capillaries?
Fluid movement out of the capillary is mediated by the balance of pressures (hydrostatic and oncotic) --> not much movement out of capillary due to hydrostatic and oncotic pressures --> low hydrostatic pressure makes lung less likely to experience edema than other circulations

CRRAB II Week 5 (12 decks)

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