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Spring 2020 - Physiology 1 > Pulmonary & Bronchial Circulation - Quiz 3 > Flashcards

Pulmonary & Bronchial Circulation - Quiz 3 Flashcards

1
Q

Factors that vary blood flow throughout lung

A

Vascular Pressures

Gravity

Distensible Pulmonary Vessels

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2
Q

The right ventricle ejection fraction into the lungs is equal to what?

A

Left Ventricular Cardiac Output

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3
Q

Why is pulmonary pressure lower than systemic pressure?

A

Pulmomary flow is 10 x LESS resistant than systemic circulation

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4
Q

Describe the wall of the Pulmonary Artery

A

Thin & Compliant - 1/3 thickness of Aorta

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5
Q

What are the Pulmonary Vessels Divided Into

A

Alveolar and Extra-Alveolar

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6
Q

Alveolor Vessels

A
  • Related to Acini
  • Capillary network gas exchange
  • Directly affected by alveolar pressure
  • High Positive pressure during lung expansion collapses vessels
  • Capillaries can be compressed so that they contain no blood
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7
Q

Extra-Alveolar Vessels

A
  • the arteries and veins that move blood to/from respiratory units
  • Large vessels: thick walls and connective tissue
  • Not effected by lung pressures
  • No compression during positive pressure
  • Lung tissues pull these vessels open during lung volume expansion
  • Bronchial Vessels: oxygenated blood from systemic circulation, 1-2% CO, empty into left atrium
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8
Q

Alveolar vessels provide what kind of resistance to flow?

A

Longitudinal

2 Ways: Dimensions and Distensibility

(Dimensions NOT controlled by autonomic or hormonal)

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9
Q

??????What are the mechanisms to decrease pulmonary vascular resistance as vascular pressures are raised

A

Recruitment (opening of closed vessels)

and

Distension (Increase in Caliber of Vessels)

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10
Q

Pulmonary Capillaries

A
  • Covers 70-80% of alveolar surface area
  • Total Capillary surface area almost equals alveolar surface area
  • RBC travels 600-800 micrometers thru network
  • Blood volume = RV stroke volume
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11
Q

Functional Capillary Volume

A
  • Capillary volume increased by opening closed segments (recruitment)
  • 1mL/kg normal volume (70mL)
  • 200 mL at max volume
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12
Q

How long does RBC remain in capillary network?

A

One Cardiac Cycle - 0.75 sec

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13
Q

How much time does RBC need for gas exchange in the capillary network?

A

Less than 0.25 Seconds

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14
Q

Pulmonary Circulation Volume

A
  • TBV from pulmonary artery to LA: 500 mL
  • Lung is 40%-50% blood by weight; > than any other organ
  • Reservoir for LA, can alter volume from 50% to 200%
  • Prevents blood return to RV from affecting LV diastolic fillimg pressures over 2-3 cardiac cylces
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15
Q

How does increased CO effect Pulmonary Vascular Pressures?

A

Increases Pulmonary Pressure, but Decreases Pulmonary Resistance

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16
Q

When does Recruitment Occur

A

During stress and increased tissue oxygen demand

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17
Q

What is the chief mechanism for Decrease in Pulmonary Vascular Resistance

A

Recruitment

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18
Q

What is Capillary Distension

A

Rise in internal vessel pressure - open capillary beds

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19
Q

Elevated pressures in the _________ distends capilary beds.

A

Left Atrium

(Mitral Regurgitation, LV Failure)

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20
Q

Capillary Distension

A

Leads to Lung Congestion and Heart Failure

Occurs at High Pulmonary Vascular Pressures

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21
Q

What Happens to Capillary Volume During Exercise

A
  • CO Increase
  • Increase Pulmonary Arterial Pressure
  • More Recruitment
  • Volume doubles to give time for gas exchange during increased blood flow
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22
Q

Pulmonary Blood Flow on Inspiration

A
  • Greater Subatmospheric Pleural Pressure
  • Increased pressure gradient for blood flow into thorax
  • RV gets greater volume in diastole
  • Increase venous blood return into thorax
  • LV ejects less blood due to increased pressure gradient b/t LV and systemic pressures
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23
Q

Pulmonary Blood Flow on Expiration

A
  • Lower Pleural Pressure Gradient
  • More positive thoracic pressure DECREASES venous blood return
  • Decreased pressure gradient prevents venous blood return to RV
  • Less RV ejection pressure
  • Reduce gradient b/t LV and Systemic arteries allows increased stroke volumes
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24
Q

How does PVR change with Lung volume close to FRC

A

Minimal Change

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25
Q

How does Higher and Lower lung volumes effect Pulmonary Vascular Resistance

A

Increased PVR

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26
Q

What happens to Extra-Alveolar vessels during Inspiration?

A

Dilation

  • Diameter increased by radial traction and flow resistance
  • Vessels receive more blood volume as higher alveolar pressure compresses vessels
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27
Q

What happens to alveolar vessels during inspiration?

A

Compression

  • Capillary resistance increase during elevated alveolar pressures
  • Pulmonary capillaries - major vascular resistance
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28
Q

How does mechanical positive pressure ventilation effect Alveolar pressure

A

Increases alveolar pressure

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29
Q

How does mechanical Ventilation effect Zone 2 Lung Volume

A

Increases amount of Zone 2 Lung Volumes relative to pulmonary venous pressure

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30
Q

How does the rise in Alveolar Pressure effect Zone 2

A

Increases resistance to blood flow in Zone 2

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31
Q

Positive-Pressure Ventilation can _______ CO or ________ V/Q imbalance.

A

Decrease CO and Increase V/Q Imbalance

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32
Q

What lung structures does the oxygenated blood from the aorta nourish?

A
  • Conducting airways to Terminal Bronchials
  • Parenchyma - pleura, interlobal septal tissues, pulmonary arteries and veins
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33
Q

How much Bronchial Blood Circulation returns to where via which vein?

A

50% returns to Right Atrium via Azygos Vein

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34
Q

How does the other 50% of bronchial blood exit lungs?

A

Exits through small anastomoses with pulmonary veins contributing to normal venous admixture - right-to-left shunt

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35
Q

What system is critical to keep alveoli free of fluid moving from capillaries?

A

Lymphatic System

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36
Q

What forces tend to move fluid out of capillaries and how fast?

A

Hydrostatic starling forces at 20mL/hr

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37
Q

Interstitium

A

Lymphatics drain fluid from interstitium

Kept at a slight negative pressure

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38
Q

Fick Principle

A
  • Method to measure CO, blood flow through lungs per minute
  • O2 Consumption/min = Oxygen uptake by blood in lungs/min
    • VO2 at rest: 300 mL/min
  • Measures arterial and mixed venous blood and determines O2 consumption
  • CO = O2 consumption (VO2) / Arteriovenous [O2] difference
39
Q

Indicator Dilution Principle

A
  • Inject Dye into venous circulation
  • Diluted concentration measured on arterial side
  • Thermodilution technique also used to measure CO
40
Q

How does Gravity effect Systemic BP

A
  • Degree of pressure change from heart level
  • Pressure gradient of 0.74 mmHg / cm
  • Postural dependent relationship with gravity
  • Supine: Arterial pressure feet > head
41
Q

How does Gravity effect Pulmonary Circulation

A
  • Greater changes in flow occur because pulmonary pressures are much lower
  • Distribution of blood flow in lung affected by gravity
  • Changes in pulmonary arterial pressure effect distribution of blow flow over height of lung
42
Q

How does exercise effect blood flow to Lungs?

A

Converts entire lung to Zone 3 Flow

Increases blood flow 4-7x

43
Q

What is Hydrostatic Pressure

A

The Pressure Effect gravity has on a Column of Fluid

  • Alters potential energy of the fluid column
44
Q

What are considered the Zero Reference Points?

A

The Right Atrium

and

Middle of Lung

45
Q

How does Supine or Prone position effect Hydrostatic Pressure

A

Hydrostatic Pressures are minimized

46
Q

How is Lung Perfusion effected by Gravity?

A
  • Bottom/base of lung gets more of RV ejection fraction than the top of lung
  • Hydrostatic pressure cause distension and recruitment of pulmonary capillaries in base of lung
47
Q

What does Blood flow to Lungs depend on?

A

Pressures in Pulmonary vessels relative to Alveolar Pressure

  • Pressures depend on:
    • Hydrostatic Pressure
    • Gravity
    • Transmural Compressive Pressure
    • Lung Volume
48
Q

Lung Perfusion Zone 1

A

Does NOT receive blood flow

  • PA > Pa: Alveolar pressure > Regional pulmonary blood pressure
  • Pulmonary capillaries are collapsed by higher PA
49
Q

Lung Perfusion Zone 2

A

Arterial-Alveolar Pressure Gradient drives Blood Flow

  • Pa > PA > Pv
  • Intermittent blood flow
  • Water Fall effect - downstream venous pressure changes do not alter flow
50
Q

Lung Perfusion Zone 3

A

Lung Base d/t Gravity

  • Pa > Pv > PA
  • Hydrostatic pressure cause distension and recruitment of pulm. capillaries -> decreases resistance to blood flow
51
Q

Lung Perfusion Zone 4

A

Abnormal Condition of Reduced Blood Flow

  • Pa > Pi > Pv > PA
  • High Pulmonary Venous Pressure (LV Failure, Mitral Stenosis)
  • Pulmonary edema - vascular cuffing
  • Increased Vascular Resistance & reduced local blood flow
52
Q

What are Lung Pressures dependent on?

A

Hydrostatic Pressure

Gravity

Transmural Compressive Pressure

Lung Volume

53
Q

What creates the Lung Zones

A

Differences of Pulmonary arterial, venous, and alveolar pressures

54
Q

What Factors Expand Zone 1

A
  • Decreased Pulmonary Artery Pressure - shock, hypovolemia
  • Increased Alveolar Pressure - PEEP
  • Occlusions - PE
55
Q

Factors that Reduce Zone 1

A
  • Increased Pulmonary Artery Pressure - IVF, Blood Infusion
  • Reduced Hydrostatic Effect - change in position, standing to supine
56
Q

Pressure Flow Curves

A

Pulmonary-Hemodynamic Curve

  • Assesses driving pressurs across pulmonary vasculature as CO varies
  • Increased PA pressures w/ increased CO (exercise)
  • PVR is change in pressure over CO
  • PVR = Slope of line from point of orgin to point on curve
  • Hypoxia raises resistance over entire curve
57
Q

Pulmonary Vascular Resistance

A

Active Regulation of Blood Flow

  • Active regulation occurs by altering vascular smooth muscle tone in arterioles
  • Pulmonary capillary smooth muscle alters PVR
  • Vasomotor tone of pulmonary vessels affected by many things
58
Q

Vascular Innervation

A
  • Motor innervation from sympathetic branch of Autonomic Nervous System
    • Increase in sympathetic outflow = vasoconstriction - stiffening
  • Sensory Innervation Adventitia - vascular stretching and chemicals
59
Q

What is the most active regulation pulmonary vessels mediated by?

A

Local Metabolic Influences

60
Q

Pulmonary Vasoconstrictors

A
  • Reduced PAO2
  • Increased PCO2
  • Histamine
  • Thromboxane A2
  • Alpha-Catecholamines
  • Norepi
  • Angiotensin
  • Serotonin
61
Q

Pulmonary Vasodilators

A

Increased PAO2

Nitric Oxide

Beta Catecholamines

Dopamine

Prostacyclin

62
Q

Thromboxane A2

A

Potent Local Vasoconstrictor

  • Product of cell membrane arachidonic acid metabolism
  • Constrictor of Pulmonary Arterial & Venous smooth muscle
  • Produced during acute lung tissue damage by macrophage, leukocytes, and endothelial cells
  • Effect localized to injured region d/t half-time of thromboxane inactivation is only seconds
63
Q

Prostacyclin

A

Prostaglandin I2 - Potent Vasodilator

  • Inhibits platelet activation
  • Produced by endothelial cells
  • Product of arachidonic acid metabolsim
64
Q

Nitric Oxide

A

Epithelial Vasodilator

  • Potent endothelium-derived endogenous vasodilator
    • Strictly localized effect
    • Formed from L-arginine lead to smooth muscle relaxation through synthesis of cyclic GMP
  • ​Activates guanylyl cyclase and increases cGmp
  • Basis for how Nitroglycerin and Sodium Nitroprusside wrok
  • Very Toxic
    • Methemoglobinemia - HGB doesnt let go of oxygen to tissues
65
Q

What is the critical factor governing pulmonary circulation?

A

Partial Pressure of Oxygen (PAO2) in Alveoli

66
Q

PO2 in alveoli is _________ important than oxygen tension in mixed venous blood

67
Q

What does Oxygen Diffusion into Pulmonary Arteriole Walls Cause?

A

Cause Smooth muscle dilation

  • As alveolar oxygen tension decreases - surrounding aterioles constrict
  • Low alveolar PO2 - increase in local vascular resistance
  • Blood flow shifted to area of lung with higher PO2
  • These small changes in local resistance do not effect overal PVR
    • (If < 20% of lung volume involved)
68
Q

How does global reduction in alveolar oxygen tension effect PVR?

A

Increases total PVR by constriction of arterioles and small arteries

69
Q

What does Alveolar Hypoxia Cause

A

Hypoxic Pulmonary Vasoconstrction (HPV)

  • Localized response of pulmonary arterioles
  • Enahnced by hypercapnia and acidosis
  • Contraction of smooth muscles in region of hypoxia
  • Important mechanism of balancing V/Q ratio
    • Shift of flow to better ventilated areas
    • Happens because less Nitric Oxide in hypoxic area.
70
Q

Pulmonary HTN

A
  • High PVR
    • Generalized alveolar hypoxia increases total pulmonary resistance
    • Hypoventilation
    • Low Inspired PO2, Increased PCO2
    • Pain
    • Histamine Release
    • High Altitudes
71
Q

What causes increased work for the Right Ventricle?

A

Pulmonary HTN

  • RV Hypertrophy
  • Tricuspid Regurg
  • Right Heart Failure - Cor Pulmonale
72
Q

Pulmonary HTN is considered a _________ pumonary vascular condition

A

SERIOUS

  • Narrowing of small musclar pulm. arteries
  • Increase in pulm. arterial pressure
  • RV pressures rise to compensate until failure
  • Lung Transplant ONLY effective treatment
73
Q

Distribution of Ventilation

A
  • Normal lung is more ventilated at base
  • Difference between regional & local ventilation due to differences in airway resistance, compliance, and hydrostatic effects
74
Q

Regional Nonuniform Ventilation

A
  • Gravity causes hydrostatic interpleural pressure gradient
    • Alveoli more expanded at top of lung than base
    • Alveolar volume parallels lung compliance curve
  • Regional lung volume changes vary b/c transpulmonary pressures influenced by interpleural pressure gradient
  • Differences in transpulmonary pressure affect lung compliance
75
Q

What causes Local Nonuniform Ventilation

A

Variable Airway Resistance and Localized Difference in Compliance

  • Healthy lungs have equal constants in all acini
  • Acini ventilation not as effected by hydrostatic pressure changes
76
Q

Lower Lung Ventilation vs Apex of Lung

A

More ventilation to base than to top

  • FRC is less at base
  • Base compliance > Top compliance
77
Q

Local Ventilation Distribution

A
  • Ventilation not even throughout lung
  • Time constant establishes rate of acinar volume change
  • Longer time constant = Slower Ventilation of Lung Unit
  • Increased Resistance and/or Decreased Compliance = Longer Alveolar Filling Time
  • Decreased compliance (stiff lung) reduces lung volume changes
78
Q

V/Q Matching

A

Maintains PaO2 of 85-100 mmHg

  • Distribution of VQ ratios not normally uniform
79
Q

Alveolar-Arterial (A-a) PO2 Differences

A

Express Unequal Match of V/Q

  • Normal PO2 differences are 10-15 mmHg
  • Larger PO2 gradients indicate intrinsic pulm. disease - > shunting
  • Hypoxemia with normal PO2 gradient -> hypoventilation
  • V/Q mismatch is most common cause of inefficient gas exchange
  • Wasted ventilation & venous admix cause abnormal PO2 differences.
80
Q

Right to Left Heart Shunt

A

Pulmonary Venous Admixture

  • Shunt = Perfused but not Ventilated
  • Reduces systemic arterial oxygen tension and concentration
  • Reduce efficiency of gas exchange
  • Small shunts are normal b/c some venous blood bypasses lung to left heart

(Allowing nonoxygenated right side heart blood to the left)

81
Q

True Anatomical Shunts

A

Bronchopulmonary Venous Anastomoses

Intracardiac Thesbian Veins

Mediastinal Veins

Pleural Veins

82
Q

What is Venous admixture of blood equivalent to?

A

Wasted Ventilation

83
Q

Left-to-Right Heart Shunt

A

Pulmonary Venous Recirculation

  • Part of CO returns to right heart without flowing through body
  • Does not affect systemic arterial oxygen tension
  • Increased Right Heart oxygen tension
    • Location of increased oxygen concentration indicates site of L-to-R shunt
    • Amount of change PO2 allows estimate of shunt
84
Q

What kind of Regualtion of blood flow through capillaries occur in response to changes in Cardiac Output

A

Passive Regulation

  • Increases blood flow - recruitment & distension
  • Prevent rise in Pulmonary pressure with increase in blood flow
85
Q

How much do alveolar walls contribute to total resistance?

86
Q

How much do alveolar arterioles contribute to resistance?

87
Q

How much do arterioles contritubute to systemic circulation resistance?

88
Q

Right Atrial Pressure

89
Q

Left Atrial Pressure

A

6 - 12 mmHg

90
Q

Right Ventricle Pressure

91
Q

Left Ventricule Pressure

A

120/0 mmHg

92
Q

Pulmonary Capillary Pressure

93
Q

Pulmonary Artery Pressure

A

25/8 mmHg

Mean: 15

94
Q

Pressure of the aorta

A

120/80

Mean: 90

Spring 2020 - Physiology 1 (24 decks)

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