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physiology IV > Pulmonary Circulation > Flashcards

Pulmonary Circulation Flashcards

1
Q

What is the only vascular bed to receive the entire cardiac output?

A

pulmonary circulation

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2
Q

Is the series circulation in parallel or series with the pulmonary circulation?

A

series

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3
Q

Why is ischemic damage rare in the lung?

A

multiple supplies of O2

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4
Q

Why is the pulmonary blood pressure lower than the systemic blood pressure?

A

vascular resistance is less than TPR

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5
Q

Is the afterload lower in the left ventricle or right ventricle?

A

right ventricle

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6
Q

What is the normal anatomic shunt and what percentage of CO does it carry?

A

Left to left shunt

1-2% of cardiac output

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7
Q

Where does the lymphatic system drain into ?

A

caudal mediastinal lymph node and thoracic duct

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8
Q

How are the valves of the lymphatic system regulated?

A
  • By mechanical pumping during breathing

- by sympathetic activity

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9
Q

Are there arterioles in the pulmonary circulation?

A

No

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10
Q

Why does pulsatile pressure still exist in the pulmonary circulation?

A

Since resistance is so low

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11
Q

What is the mean Ppa?
What Ppa indicates pulmonary hypertension?
What Ppa indicates pulmonary edema?

A

Mean = 11 mmHg
If Mean Ppa>20 - pulm hypertension
If mean Ppa>25 - pulmonary edema

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12
Q

Diastolic P in pulmonary artery is nearly equal to what?

A

Left ventricular P

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13
Q

What occurs during exercise in the pulmonary circulation?

A
  • radius of the vessels increases and resistance therefore decreases passively
  • Compliance of the vessels is high so P doesn’t increase much

(There is not autoregulation, this all occurs passively)

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14
Q

Vessels in the alveoli are exposed to what type of P? Extraalveolar vessels are exposed to what type of P?

A

Alveolar vessels - alveolar P

extralveolar vessels - intrapleural P

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15
Q

What occurs to the alveolar blood vessels during inflation?

A
  • they are stretched and become narrower
  • radius decreases and so resistance increases
  • This reduces their pressure
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16
Q

What happens to extraalveolar blood vessels in response to inflation?

A
  • There is a more negative intrapleural P as the lung inflates
  • their transmural P increases
17
Q

What is the relationship btwn alveolar and extra-alveolar vessels? How does this affect total resistance?

A

They are in series, so resistance is additive

18
Q

When is PVR at a minimum?

A

FRC

PVR increases at any other value

19
Q

During normal breathing what is the normal alveolar pressure, and what effect does this have on the alveolar vessels?

A

alveolar P fluctuates around zero and so all the vessels remain open

20
Q

During mechanical ventilation what happens to alveolar pressure? What does this mean for you as a physician?

A

It becomes slightly positive

  • capillaries can collapse and inc their R
  • must ventilate at lowest possible P near the FRC
21
Q

Name some vasodilators that affect pulmonary vascular resistance? (4)

A
  • prostacycline
  • histamine (bronchoconstrictor)
  • calcium channel blockers
  • Nitric oxide
22
Q

What happens in the lung when a certain area is not able to be ventilated and becomes hypoxic?

A

blood is shunted to a better ventilated region of the lung by hypoxic vasoconstriction

23
Q

Name some vasoconstrictors that affect pulmonary vascular resistance? (3)

A
  • inc PCO2, low pH
  • norepinephrine - weak effect
  • angiotensin II
24
Q

In what part of the lung is blood flow greatest? Why?

A

at the base of the lung

-due to gravity and passive distension

25
Q

What happens to the pressure inside the capillaries as you distend down the lung?

A

it gradually increases

-due to the pressure from intrapleural fluid under the influence of gravity

26
Q

When a person is standing upright what is their apex pressure? What is their base pressure?

A 
Apex= Ppa -10
Base= Ppa + 10
27
Q

What zone does this describe and what occurs:

PA>Pa>Pv

A

Zone 1

  • not normally present
  • capillaries will collapse and flow stops-no perfusion
  • can occur during blood loss or cardiac output decrease
28
Q

What zone does this describe and what occurs here:

Pa>Pv> PA

A

zone 3

  • flow inc due to gravity and passive distension
  • capillaries are wide open
29
Q

How is flow determined in zone 3?

A

by the difference btwn PA-Pv

30
Q

What zone does this describe and what occurs here:

Pa>PA>Pv

A

Zone 2

-partial collapse of capillaries on low pressure side but with maintenance of flow

31
Q

How would you determine the flow in zone 2?

A

Difference btwn Pa and PA

-Pv has no effect - it is downstream

32
Q

Describe what changes in the four starling filtration pressures cause pulmonary edema?

A
  1. inc capillary permeability
  2. inc in capillary hydrostatic pressure
    - mitral valve stenosis
  3. dec interstitial hydrostatic P
  4. dec colloid osmotic P
33
Q

Does high or low protein in the blood cause pulmonary edema?

A

low protein —hypo

34
Q

In the equation: QS/QT = (C”c”O2-CaO2)/ (C”c”O2-CvO2), what occurs if QS =0?

A

normal condition of no shunt

CaO2 = C”c”O2

35
Q

In the equation: QS/QT = (C”c”O2-CaO2)/ (C”c”O2-CvO2), what occurs if QS =QT?

A

all blood is shunted - no oxygenation

CaO2 = CvO2

36
Q

In the equation: QS/QT = (C”c”O2-CaO2)/ (C”c”O2-CvO2), what occurs if QS =QT/2?

A

50% Shunt- aterial oxygen content is average of shunt and functional capillary content

-CaO2 = (C”c”O2+ CvO2)/2

37
Q

Does shunting give more hypoxemia or hypercapnea?

A

more hypoxemia due to the O2 dissociation curve

-CO2 curve is linear

38
Q

Can breathing O2 rich gas help people with abnormal shunts?

A

NO - they physically cannot be oxygenated so this is just a waste

physiology IV (40 decks)

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