Exam #3: Pulmonary Circulation Flashcards

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1
Q

How do pulmonary arteries structurally compare to the systemic arteries?

A

1) Shorter
2) More compliant
3) Thinner walled

This allows them to accomodate the entire cardiac output

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2
Q

What is the bronchial circulation?

A

Circulation to the lung parenchyma itself

  • Bronchial arteries provide oxygenated systemic blood to the lungs
  • Bronchial veins carry 1/3 of the bronchial circulation back to the RA
  • Remaining 2/3 goes to the LA via the pulmonary veins, which is responsible for the “physiological shunt” of blood
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3
Q

What is the effect of bronchial circulation?

A

Physiological shunting of blood & drop in partial pressure of oxygen in systemic circulation compared to alveolar oxygen

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4
Q

What is hypoxic pulmonary vasoconstriction (HPV)?

A
  • Decreased alevolar Po2 i.e. alveolar hypoxia (<70 mmHg) causes local vasoconstriction, which is the OPPOSITE of what happens in systemic circulation
  • Blood redistribution to better aerated alveoli i.e. serves to match ventilation & perfusion by redirecting perfusion to better oxygenated alveoli
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5
Q

What causes HPV?

A
Airway obstruction 
Failure of ventilation 
Acute lung damage 
High altitude
COPD
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6
Q

What is the long term effect of HPV?

A

Pulmonary arterial hypertension (PAH)

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7
Q

What are the effects of gravity on the distribution of pulmonary blood flow? What is the clinical significance?

A
  • Blood flow is greater in the bases of the lungs than the apex in the standing individual.
  • Clinically, this is why you look for evidence of edema at the bases of the lungs
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8
Q

Describe the structure of the pulmonary capillaries.

A

Thin walled
Leaky to protein
Low pressure
Form a sheet of flow

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9
Q

Summarize the pulmonary capillary & interstitial fluid dynamics.

A

1) Normal outward forces are greater than inward forces, which provides a filtration pressure out of the pulmonary capillaries into the interstitial space
2) Pulmonary lymphatic pressure is negative relative to interstitial, which results in the recycling of fluid

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10
Q

What causes an increased in interstitial hydrostatic pressure?

A

Edema

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11
Q

What conditions will increase intravascular hydrostatic pressure?

A

Increased blood volume

Poor heart function

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12
Q

What will decrease capillary osmotic pressure?

A

CKD

Liver disease

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13
Q

What conditions will change capillary permeability?

A

Drug toxicity
Infection
Autoimmune disease

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14
Q

What is the ventilation- perfusion relationship?

A

Matching ventilation (V) to perfusion (Q) is essential for ideal gas exchange

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15
Q

What is the average normal for V/Q?

A

0.8

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16
Q

Draw the V/Q graph.

A

N/A

Note that ventilation & perfusion decrease from the base of the lung to the apex, but perfusion decreases FASTER

17
Q

How do V & Q change from the base to the apex of the lung?

A

BOTH drop, but there is a higher V than Q at the apex than the base

18
Q

What pathological condition favors high V at the apex of the lung?

A

TB

19
Q

What is a V/Q defect?

A

Mismatch between V & Q.

20
Q

What is the V/Q relationship at the dead space? What pathologic condition results in dead space?

A

Infinity b/c no perfusion

- Pulmonary embolism; there is ventilation but no perfusion because the region is occluded by the emboli

21
Q

What does it mean that there is a high VQ?

A
  • There is high ventilation relative to perfusion (high V compared to Q)
  • Usually due to a decrease in blood flow
22
Q

What does it mean that there is low V/Q?

A
  • There is low ventilation relative to perfusion, usually because ventilation is decreased
23
Q

What is the term for VQ= 0?

A

“Shunt,” this is a portion of the lung where the CO has been diverted

24
Q

What is a right to left shunt? What are the clinical features of a right to left shunt?

A

Shunting of blood from right heart to left heart e.g. in cases of LATE stage VSD or ASD

  • Hypoxemia always occurs because blood is not going through the lungs
  • Cannot be corrected with having the person breathe high O2 gas
25
Q

What is Eisenmenger Syndrome?

A

Refers to late stage septal defects that essentially have a reversal of shunting from left to right, to right to left

  • Left to right shunting causes increased pressure to be pumped into the pulmonary arteries
  • Vascular remodeling occurs that increases the thickness of these arteries, transmitting pressure back into right heart
  • Eventually right pressure is greater than left & shut reverses direction
26
Q

Describe the pathophysiology of PE.

A

Right ventricular failure
Right to left shunting
V/Q mismatch

27
Q

What is the physiologic shunt?

A

This refers to roughly 2% of the CO that NORMALLY bypasses the alveoli

28
Q

What is a left to right shunt? What are the clinical features of a left to right shunt?

A

Shunting of blood from the left side of the heart to the right

  • DO NOT cause hypoxemia
  • E.g. patent ductus arteriosus & traumatic injury