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FHB - Pulmonary & Renal - Exam 2 > Pulmonary 5 > Flashcards

Pulmonary 5 Flashcards

1
Q

How is gas transferred across the blood brain barrier?

A

Via diffusion

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2
Q

What are the 3 factors that facilitate diffusion in the respiratory system?

A
  1. Large Surface Area
  2. Short Distances
  3. Gases with advantageous diffusion properties
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3
Q

What is Fick’s Law?

A

Vgas = Area * Diffusion constant * Difference in Partial Pressure / THICKNESS

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4
Q

The amount of gas transferred through the capillaries is proportional to what? What is it indirectly proportional to?

A

Area, Diffusion constant, and difference in partial pressure

Indirectly proportional to THICKNESS

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5
Q

What is graham’s law? What is the solubility of O2 and CO2 and how is this important for the rate of diffusion?

A

Rate of Diffusion = Solubility coefficient of the gas/ (molecular weight)^1/2

O2 = 1
CO2 = 22

Rate of diffusion of CO2 is twice as fast than the rate of diffusion of O2

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6
Q

What gasses are perfusion limited? What does this mean?

A

N2O and O2

  • their partial pressures have equilibrated with alveolar pressure before exiting the capillary

(once it hits the threshold, the concentration does not change)

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7
Q

What gas is diffusion limited? What does this mean?

A

CO

-partial pressure of CO does not reach equilibrium with alveolar pressure (can continuously increase)

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8
Q

What is O2 and CO2 uptake usually? Perfusion or Diffusion limited? When does this change

A

Perfusion limited

  • changes at LOW ALVEOLAR PO2 such as in high altitude
  • severe exercise can lead to diffusion impairment oxygen transfer in healthy people
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9
Q

Is Cardiac output different in the systemic & pulmonary circuit?

A

NO, same since it is in series
- resistance to flow through the lungs is VERY low so the pulmonary driving pressure is 6 mmHg as compared to 87 mmHg in the systemic system

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10
Q

The following describe which structure?

  1. Only Arteries with deoxygenated blood
  2. Thin wall
  3. 7x more compliant
  4. Easily Distensible
  5. Low Pressure Circulation
A

PULMONARY ARTERIES

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11
Q

During inspiration, what occurs to alveolar & extra-alveolar vessels?

A

Alveolar are compressed

Extra-alveolar are pulled open

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12
Q

What 4 factors influence lung perfusion?

A
  1. Gravity
  2. Pulmonary Vascular Resistance
  3. Alveolar Pressure
  4. Arterial-Venous pressure gradient
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13
Q

How does the lung respond to an increase in vascular pressure?

A

Decreases pulmonary vascular resistance

  1. Capillary Recruitment
  2. Capillary Distension
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14
Q

When would Capillary Recruitment & Capillary Distension occur?

A

During increased Cardiac Output

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15
Q

Why does the change in total pulmonary vascular resistance form a U shape?

A

There is a tradeoff between the increase in resistance in alveolar pressure & decrease in resistance in extra-alveolar vessels (and opposite for expiration) which forms a curve

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16
Q

What are two reasons for more blood in the base of the lung( similar to the movement of airflow)

A
  1. Gravity

2. shape of lung - forming a triangular base that allows more blood to be stored

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17
Q

Describe the 3 zones of the lung. What is the waterfall zone? Which zone only exists under abnormal conditions? Which zone only depends on the arterial/capillary and venous pressures?

A

Zone 1 - exists only under abnormal conditions
“no flow zone” - no blood can reach this because the Right Ventricle cannot pump that strongly
exists under:
1. Positive Pressure Ventilation (PA high)
2. Hypotension/Shock (Pa low)
PA>Pa>Pv

Zone 2 - Water Fall zone - blood falls down through the capillaries since the pulmonary venous pressure is below atmospheric pressure Pa>PA>Pv
- Alveolar Pressure controls the flow (not venous/arterial gradient)
“compressive flow” since alveolar pressure compresses the capillaries and collapses them slightly

Zone 3 : Normal Zone at the base of the lung –> both pulmonary arterial and venous pressure are above atmospheric pressure & ALVEOLAR pressure has NO AFFECT on the vascular resistance

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18
Q

What are 2 controls of pulmonary perfusion?

A
  1. Hypoxic Vasoconstriction

2. Local Vasoconstrictors/Vasodilators

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19
Q

What occurs to the flow of blood under Hypoxic Vasoconstriction? What determines this?

A

Determined by PO2 in ALVEOLAR gas (not by arterial PO2)

- shifts blood from hypoxic areas to well-perfused areas

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20
Q

What creates the lung fluid balance?

A

Hydrostatic & Oncotic Pressures

- STARLING FORCES!

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21
Q

What happens if the plasma water that is filtered from systemic capillaries cannot be picked up by lymphatics?

A

Engorgement of the pleural space resulting in pleural effusions at the expense of loss of lung volume

  1. Interstitial Lung Edema
    THEN
  2. Alveolar Lung Edema
22
Q

What is O2 and Co2 usually limited by? When does this change?

A

Perfusion Limited

  • Becomes diffusion limited under extreme conditions
    1. Alveolar Hypoxia
    2. Exercise
    3. Thickening of blood-gas barrier
23
Q

What would occur if the erythrocyte spend less than 0.25 seconds in the capillary bed?

A

Diffusion Limitation of CO2 and O2 (instead of perfusion limitation)

24
Q

What are two conditions when PVR increases?

A
  1. Low Volumes

2. High volumes

25
Q

What type of gas transfer is the following:

  1. N20
  2. O2 & CO2
  3. CO

(diffusion limited, perfusion limited, both)

A
  1. N20 - Perfusion limited
  2. O2 & CO2 usually perfusion limited, but during exercise/high altitude it is diffusion limited
  3. CO Diffusion limited
26
Q

What is perfusion limited transfer of gas? Does equilibrium occur? How can one increase the Partial Pressure of a gas that is perfusion limited?

A

Perfusion limited gas transfer means that the gas reaches Equilibrium fairly quickly (before passing through 1/3 of the capillary bed)

  • the only way to increase partial pressure of N2O that has reached equilibrium, would be to increase the FLOW OF BLOOD
  • insoluble gases that do not chemically combine with proteins are Perfusion Limited because their partial pressure can build up
27
Q

What is Diffusion limited transfer of gas? Does equilibrium occur? How can one increase the Partial Pressure of a gas that is perfusion limited?

A

Diffusion limited transfer of SOLUBLE gas that have a high affinity for hemoglobin

  • Little or NO increase in partial pressure so equilibrium is NOT reached for CO (linear increase)
  • transfer only depends on
    the diffusion properties of the gas
28
Q

When is the exchange of CO2 and O2 diffusion limited?

A

Heavy Exercise at High Altitude

  • the transit time of erythrocytes is very short (fast) so system cannot reach equilibrium for the gas (O2 or CO2)
  • high altitudes usually form a lower pressure gradient for O2/CO2 exchange and so gas transfer is slower
29
Q

What is the equation for Pulmonary Vascular Resistance? PVR

A

PVR = Pressure Change / Flow (Q)

30
Q

When pressure in the system increases, how does it change to reach baseline values?

A

Decrease pulmonary vascular resistance!

  • by recruiting capillaries and by distention of perfused capillaries
31
Q

What demarcates the upper boundary between zones 1 and 2?

What demarcates the LOWER boundary between zones 2 and 3?

A

Pulmonary Artery Pressure

Pulmonary VEIN pressure!

32
Q

What are 2 ways that the Pa can be lower than the PA in zone 1?

A
  1. Low cardiac output

2. Hypotension

33
Q

Which zone is based off the pressure gradient of alveolar pressure and NOT venous pressure?

A

Zone 2

34
Q

Which zone are Pulmonary Arterial & Venous pressures SUBATMOSPHERIC?

A

Zone 1!

35
Q

The PO2 in arteries determined Hypoxic Vasoconstriction.

True or False?

A

FALSE

  • determined by PO2 in ALVEOLAR gas
36
Q

What are 3 situations that change O2 diffusion from perfusion limited o DIFFUSION limited?

A
  1. Alveolar Hypoxia
  2. Exercise
  3. Thickening of blood-gas barrier (fibrosis)
37
Q

When the erythrocyte spends less than 0.25 in the capillary bed, what happens to gas exchange of CO2 and O2?

A

Changes from Perfusion limited to DIFFUSION LIMITATION

38
Q

If capillary pressure is less than alveolar pressure and the capillaries collapse and blood flow stops, which zone does this represent?

A

ZONE 1

39
Q

What is the amount of blood volume in the alveolar capillary network under resting conditions? During exercise?

A

Total blood volume is 70 mL

  • increases to 150-200 mL during exercise
  1. Capilalry recruitment
  2. Distension
40
Q

How is the Pulmonary Vascular Resistance different from Autoregulation?

A

OPPOSITE of auto regulation

  • As pressure INCREASES, the vascular resistance DECREASES due to recruitment and distention

(most of PVR lies in the capillaries)

41
Q

Where is most of the Pulmonary Vascular Resistance located?

A

CAPILLARIES

42
Q

What is the function of the perivascular sheath in the pulmonary vessel?

A

As you INHALE the whole lung expands and radial forces of the perivascular sheath pull the vessels apart

  • diameter increases so FLOW increases & resistance decreases

(high lung volumes, blood resistance decreases)

43
Q

When is PVR lowest?

A

at FRC! - intermediate point

u-shaped graph of alveolar & extra-alveolar resistance

44
Q

When is PVR the highest?

A

at VERY LOW and VERY HIGH volumes

45
Q

When does the difference in flow between the apex and base become less?

A

DURING EXERCISE!

46
Q

When is Hypoxic Vasoconstriction important?

A

During BIRTH

  • the first breath there is a dramatic decrease in PVR
  • increase in pulmonary blood flow
47
Q

What are a few pulmonary vasoconstrictors?

A
  1. ThromboxaneA2
  2. α1-adrenergic receptor agonists
  3. Angiotensin
  4. Leukotriens
  5. Neuropeptides
  6. Serotonin
  7. Endothelin
  8. Histamine
  9. Prostaglandins
  10. High CO2
48
Q

High CO2 causes constriction or dilation?

A

Vasoconstriction!

49
Q

What are a few pulmonary vasodilators?

A
  1. Prostacyclin
  2. B1-adrenergic receptor agonists
  3. Nitric oxide (NO)
  4. Acetylcholine
  5. Bradykinin
  6. Dopamine
50
Q

When are the effects of vasoconstrictors/dilators most important?

A

PATHOLOGICAL CONDITIONS!

  • not important under normal circumstances
51
Q

PVR is low, and falls even lower when?

A

During an increase in Cardiac Output!

FHB - Pulmonary & Renal - Exam 2 (21 decks)

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