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Lange Pulmonary Physiology, 10e > Chapter 4 > Flashcards

Chapter 4 Flashcards

1
Q

What are the main objectives of studying blood flow to the lung?

A

To understand the structure, function, distribution, and control of the blood supply of the lung

This includes comparing bronchial and pulmonary circulation, explaining physiological consequences, and understanding the effects of lung volume and pressures on pulmonary vascular resistance.

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2
Q

What constitutes pulmonary blood flow (PBF)?

A

The entire output of the right ventricle supplying the lung with mixed venous blood

This blood undergoes gas exchange with alveolar air in the pulmonary capillaries.

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3
Q

How much blood is typically present in the pulmonary circulation per square meter of body surface area?

A

250 to 300 mL

About 60 to 70 mL/m2 of this blood is located in the pulmonary capillaries.

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4
Q

What is the average time a red blood cell takes to travel through the pulmonary circulation at resting cardiac output?

A

4 to 5 seconds

Approximately 0.75 seconds of this time is spent in the pulmonary capillaries.

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5
Q

What is the diameter of pulmonary capillaries compared to erythrocytes?

A

Pulmonary capillaries average around 6 mm; erythrocytes are about 8 mm

Erythrocytes must change shape slightly to pass through the smaller pulmonary capillaries.

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6
Q

What is the estimated potential surface area for gas exchange in the lungs?

A

50 to 100 m2

This is due to approximately 280 billion pulmonary capillaries supplying about 300 million alveoli.

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7
Q

What do bronchial arteries supply?

A

Arterial blood to the tracheobronchial tree and other lung structures down to the terminal bronchioles

They also supply the hilar lymph nodes, visceral pleura, pulmonary arteries and veins, vagus, and esophagus.

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8
Q

What percentage of the left ventricle’s output does bronchial circulation constitute?

A

About 2%

Blood pressure in bronchial arteries is comparable to systemic arteries.

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9
Q

True or False: The venous drainage of bronchial circulation enters the pulmonary veins.

A

True

This results in bronchial venous blood mixing with ‘arterial’ blood in the pulmonary veins.

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10
Q

What is Poiseuille’s law used for in pulmonary physiology?

A

To estimate pulmonary vascular resistance (PVR)

It relates pressure difference, flow, and resistance in a tube.

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11
Q

What is the formula for calculating pulmonary vascular resistance (PVR)?

A

PVR = (MPAP - MLAP) / PBF

MPAP is mean pulmonary artery pressure, MLAP is mean left atrial pressure, and PBF is pulmonary blood flow.

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12
Q

How does the resistance to blood flow in the pulmonary circulation compare to the systemic circulation?

A

PVR is about one-tenth that of systemic vascular resistance (SVR)

This is due to the structural differences in the pulmonary circulation.

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13
Q

What is the distribution of pulmonary vascular resistance across the pulmonary vasculature?

A

About one-third in pulmonary arteries, one-third in capillaries, and one-third in pulmonary veins

In contrast, about 70% of resistance in systemic circulation is in systemic arteries.

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14
Q

What is the primary determinant of pulmonary vascular resistance?

A

Transmural pressure difference across vessel walls

This reflects the change in pressures due to the surrounding alveolar and intrapleural pressures.

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15
Q

Fill in the blank: The pulmonary artery and its branches are much ______ than corresponding parts of the systemic circulation.

A

thinner walled

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16
Q

What happens to blood pressure as you move up from the heart to the head?

A

Blood pressure decreases

This is due to the effect of gravity on the column of blood.

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17
Q

What is the significance of the high arterial pressure in the systemic circulation?

A

It allows for redistribution of left ventricular output and control of blood flow to different tissues

This is necessary for supplying all body tissues with blood.

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18
Q

What must the left ventricle maintain to overcome hydrostatic forces and pump blood to the brain?

A

A relatively high mean arterial pressure

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19
Q

Why is high arterial pressure in systemic circulation necessary?

A

It allows the redistribution of left ventricular output and control of blood flow to different tissues

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20
Q

What happens to blood vessels supplying exercising muscle during exercise?

A

They dilate in response to increased local metabolic demand

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21
Q

What is the effect of increased resistance to blood flow in other vascular beds?

A

It helps maintain blood pressure

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22
Q

In pulmonary circulation, why are redistributions of right ventricular output usually unnecessary?

A

All alveolar-capillary units participating in gas exchange perform the same function

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23
Q

What is the workload of the left ventricle compared to the right ventricle?

A

The workload of the left ventricle is much greater

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24
Q

What factors have a profound effect on pulmonary vascular resistance (PVR)?

A

Gravity, body position, lung volume, alveolar and intrapleural pressures, intravascular pressures, right ventricular output

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25
Q

What determines the vessel diameter in distensible-compressible vessels?

A

The transmural pressure difference

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26
Q

How does increased transmural pressure difference affect vessel diameter?

A

Increases vessel diameter and decreases resistance

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27
Q

What happens to the pulmonary capillaries as lung volume increases during inspiration?

A

They are elongated and their diameters decrease

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28
Q

At which lung volume is pulmonary vascular resistance (PVR) lowest?

A

Near the functional residual capacity (FRC)

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29
Q

What occurs to the resistance of extraalveolar vessels at higher lung volumes?

A

It decreases due to increased transmural pressure and radial traction

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30
Q

What is the effect of mechanical positive-pressure ventilation on PVR?

A

It elevates PVR throughout the respiratory cycle

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31
Q

What are the two mechanisms by which increased mean pulmonary artery pressure may decrease PVR?

A

Recruitment and distention

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32
Q

What is recruitment in the context of pulmonary capillaries?

A

The opening of previously unperfused capillaries due to increased perfusion pressure

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33
Q

What happens to PVR when cardiac output or pulmonary artery pressure decreases?

A

It can result in derecruitment of pulmonary capillaries

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34
Q

What effect does increased pulmonary artery pressure have on pulmonary vascular resistance?

A

Decreases due to recruitment and distention

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35
Q

What type of influences can alter pulmonary vascular smooth muscle activity?

A

Neural and humoral influences

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36
Q

Fill in the blank: Increased lung volume above FRC _______ PVR.

A

Increases

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37
Q

Fill in the blank: Positive intrapleural pressure _______ PVR.

A

Increases

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38
Q

What is the relationship between blood viscosity and PVR?

A

Increased blood viscosity increases resistance

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39
Q

True or False: The resistance of alveolar and extraalveolar vessels is additive at any lung volume.

A

True

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40
Q

What is the term for the volume of air remaining in the lungs after a normal expiration?

A

FRC (functional residual capacity)

FRC is essential for maintaining adequate gas exchange.

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41
Q

What effect does gravity have on pulmonary blood flow?

A

Decreases in gravity-dependent regions of the lungs

Gravity affects the hydrostatic pressure and subsequent blood flow in the lungs.

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42
Q

What are the hydrostatic effects that influence pulmonary blood flow?

A

Recruitment and distention

These effects lead to increased interstitial pressure and compression of vessels.

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43
Q

How does positive-pressure ventilation affect alveolar pressure?

A

Increases alveolar pressure

This increase can lead to compression and derecruitment of alveolar vessels.

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44
Q

What is the relationship between viscosity and resistance in the pulmonary circulation?

A

Viscosity directly increases resistance

Increased blood viscosity leads to greater resistance to blood flow.

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45
Q

What are the active influences on pulmonary vascular resistance that can increase it?

A
  • Stimulation of sympathetic innervation
  • Norepinephrine, epinephrine
  • α-Adrenergic agonists
  • PGF2α, PGE2
  • Thromboxane
  • Endothelin

These factors contribute to increased pulmonary vascular resistance.

46
Q

What effect does alveolar hypoxia have on pulmonary vascular resistance?

A

Causes pulmonary vasoconstriction

Alveolar hypoxia is a significant factor leading to increased resistance.

47
Q

True or False: The pulmonary vasculature is innervated by both sympathetic and parasympathetic fibers.

A

True

However, the innervation is relatively sparse compared to systemic vessels.

48
Q

What is Fick’s Principle in relation to total pulmonary blood flow?

A

The total amount of oxygen absorbed by the body per minute must equal cardiac output times the difference in oxygen content between arterial and mixed venous blood

This principle is used to calculate cardiac output based on oxygen consumption.

49
Q

What is the Indicator Dilution Technique used for?

A

Determining cardiac output

It involves injecting a known amount of dye and measuring concentration changes.

50
Q

Fill in the blank: The _______ technique involves injecting cold fluid and monitoring the temperature change to calculate cardiac output.

A

Thermal dilution

This method requires a specific type of catheter for accurate measurements.

51
Q

What happens to the regional distribution of pulmonary blood flow when a subject lies down?

A

Perfusion to the anatomically upper and lower portions of the lung becomes roughly evenly distributed

Gravity still influences blood flow per unit volume.

52
Q

What is the effect of exercise on pulmonary blood flow?

A

Increases blood flow per unit volume to all regions of the lung

Despite the increase, the perfusion gradient still persists.

53
Q

What is the primary reason for the gradient of regional perfusion in the lung?

A

Gravity

The hydrostatic effects of gravity lead to greater intravascular pressures in lower regions.

54
Q

What happens to pulmonary blood flow in the uppermost regions of the lung during low pump outputs?

A

No blood flow is received

This occurs due to low pulmonary artery pressure.

55
Q

What is the effect of gravity on pulmonary blood flow (PBF) in the lungs?

A

There are significant variations in PBF within a given horizontal plane of the lung due to local factors and mechanical stresses.

56
Q

What happens to lung perfusion when alveolar pressure equals pulmonary arterial pressure?

A

Perfusion of the lung ceases because the transmural pressure across capillary walls becomes negative.

57
Q

Define zone 1 in the context of lung perfusion.

A

Zone 1 is where PA > Pa > Pv, resulting in no blood flow; it is considered alveolar dead space.

58
Q

In which zone does blood flow occur, and what is the condition of pressures?

A

Zone 2: Pa > PA > Pv, where blood flow occurs due to effective driving pressure being Pa - PA.

59
Q

What characterizes zone 3 of the lung?

A

Zone 3: Pa > Pv > PA, where blood flow is driven by pulmonary artery pressure minus pulmonary vein pressure.

60
Q

What determines the boundaries between the zones of the lung?

A

The boundaries are dependent on physiologic conditions and are not fixed anatomical landmarks.

61
Q

True or False: Hypoxic pulmonary vasoconstriction occurs throughout the lung during localized hypoxia.

A

False; it occurs locally in response to alveolar hypoxia.

62
Q

What is the mechanism of hypoxic pulmonary vasoconstriction?

A

It involves inhibition of potassium currents in vascular smooth muscle, leading to depolarization and contraction.

63
Q

Fill in the blank: Hypoxic pulmonary vasoconstriction begins at alveolar PO2s in the range of _______.

A

100 to 150 mm Hg.

64
Q

What is the physiological function of hypoxic pulmonary vasoconstriction?

A

It diverts mixed venous blood flow away from poorly ventilated areas to better-ventilated areas.

65
Q

How does positive-pressure ventilation affect pulmonary blood flow (PBF)?

A

It decreases PBF by decreasing right ventricular preload and increasing right ventricular afterload.

66
Q

What is pulmonary edema?

A

Pulmonary edema is the extravascular accumulation of fluid in the lung, impairing gas transfer.

67
Q

What does the Starling equation describe?

A

The movement of liquid across the capillary endothelium.

68
Q

What factors are included in the Starling equation?

A
  • Kf (capillary filtration coefficient)
  • Pc (capillary hydrostatic pressure)
  • Pis (interstitial fluid hydrostatic pressure)
  • σ (reflection coefficient)
  • πpl (plasma colloid osmotic pressure)
  • πis (interstitial fluid colloid osmotic pressure)
69
Q

What happens to the surface area of the alveolar-capillary barrier in relation to the Starling equation?

A

The surface area is included in the Kf value, affecting fluid movement.

70
Q

In what scenario does hypoxic pulmonary vasoconstriction become a strong response?

A

It can be strong during whole-lung hypoxia, such as at high altitude or in hypoventilation.

71
Q

What is the alveolar-capillary barrier?

A

The interface between the alveoli and pulmonary capillaries that facilitates gas exchange.

It plays a crucial role in determining fluid movement and pulmonary edema.

72
Q

What does Pc represent in the context of the Starling equation?

A

Capillary hydrostatic pressure.

73
Q

What does Pis represent?

A

Hydrostatic pressure of the interstitial fluid.

74
Q

What is the reflection coefficient (σ)?

A

It describes the ability of the membrane to prevent extravasation of solute particles such as plasma proteins.

75
Q

What does πpl stand for?

A

Colloid osmotic (oncotic) pressure of the plasma.

76
Q

What is πis?

A

Colloid osmotic pressure of the interstitial fluid.

77
Q

What is Kf in the context of the alveolar-capillary barrier?

A

A factor that includes the surface area of the alveolar-capillary barrier.

78
Q

What is the significance of the Starling equation in pulmonary edema?

A

It helps categorize potential clinical causes of pulmonary edema.

79
Q

What are some factors that predispose to pulmonary edema?

A
  • Increased capillary permeability (Kf, σ)
  • Increased capillary hydrostatic pressure (Pc)
  • Decreased interstitial hydrostatic pressure (Pis)
  • Decreased colloid osmotic pressure (πpl)
  • Insufficient pulmonary lymphatic drainage.
80
Q

Which clinical problems are associated with increased capillary permeability?

A
  • Acute respiratory distress syndrome
  • Oxygen toxicity
  • Inhaled or circulating toxins.
81
Q

What can cause increased capillary hydrostatic pressure?

A
  • Increased left atrial pressure
  • Overadministration of intravenous fluids.
82
Q

What conditions may lead to decreased interstitial hydrostatic pressure (Pis)?

A
  • Too rapid evacuation of pneumothorax
  • Upper airway obstruction.
83
Q

What are some causes of decreased colloid osmotic pressure (πpl)?

A
  • Protein starvation
  • Dilution of blood proteins by intravenous solutions
  • Renal problems resulting in urinary protein loss.
84
Q

What can lead to lymphatic insufficiency in the lungs?

A
  • Tumors
  • Interstitial fibrosing diseases.
85
Q

True or False: Pulmonary edema can occur after head injury.

A

True.

86
Q

What is the estimated normal capillary hydrostatic pressure?

A

About 10 mm Hg.

87
Q

What happens when pulmonary capillary hydrostatic pressure increases dramatically?

A

It can lead to increased filtration of fluid across the capillary endothelium.

88
Q

What is the role of interstitial hydrostatic pressure in pulmonary edema?

A

A more negative interstitial pressure increases the tendency for pulmonary edema to develop.

89
Q

How does the reflection coefficient affect fluid movement?

A

More solute leaving the capillaries leads to more fluid movement out of the vascular space.

90
Q

What is the normal range for plasma colloid osmotic pressure?

A

25 to 28 mm Hg.

91
Q

What can happen with increased concentration of solute in the interstitium?

A

It will pull fluid from the capillaries.

92
Q

What is the relationship between pulmonary vascular resistance (PVR) and lung volume?

A

PVR is usually lowest at functional residual capacity and increases at higher and lower lung volumes.

93
Q

What factors can decrease pulmonary vascular resistance?

A
  • Increases in pulmonary blood flow
  • Pulmonary artery pressure
  • Left atrial pressure
  • Pulmonary capillary blood volume.
94
Q

Where is there more blood flow in the lungs?

A

In the lower regions compared to the upper regions.

95
Q

What effect does alveolar hypoxia have on pulmonary vessels?

A

It can cause constriction of precapillary pulmonary vessels.

96
Q

What is a common condition associated with pulmonary edema?

A

Left ventricular failure.

97
Q

Fill in the blank: The Starling equation is very useful in understanding the potential causes of _______.

A

pulmonary edema.

98
Q

What does an increase in pulmonary capillary hydrostatic pressure lead to?

A

Increased filtration of fluid into the pulmonary interstitium.

99
Q

What is the clinical significance of pulmonary vascular congestion?

A

It decreases lung compliance and gas diffusion.

100
Q

What happens to pulmonary edema fluid when the patient is in an upright position?

A

It collects in lower regions of the lungs, allowing better gas exchange in upper parts.

101
Q

What is the title of the textbook authored by Levitzky, Cairo, and Hall?

A

Introduction to Respiratory Care

Published by WB Saunders and Company in 1990.

102
Q

What is the main topic of the article by Luecke and Pelosi?

A

Positive end-expiratory pressure and cardiac output

Published in Crit Care in 2005.

103
Q

What condition is discussed in the chapter by Matthay and Martin?

A

Pulmonary edema and acute lung injury

Found in Murray & Nadel’s Textbook of Respiratory Medicine, 5th ed.

104
Q

What physiological phenomenon is explored by Moudgil, Michelakis, and Archer?

A

Hypoxic pulmonary vasoconstriction

Discussed in J Appl Physiol in 2005.

105
Q

Who authored ‘The Normal Lung’ and when was the first edition published?

A

Murray JF; first edition published in 1976

Published by WB Saunders and Company.

106
Q

What is the focus of the 2nd edition of ‘The Normal Lung’ by Murray JF?

A

Continued exploration of pulmonary function

Published in 1986 by WB Saunders and Company.

107
Q

What is the main question addressed in the article by Ward and Aaronson?

A

Mechanisms of hypoxic pulmonary vasoconstriction

Published in Respir Physiol in 1999.

108
Q

What topic does West JB cover in ‘Ventilation/Blood Flow and Gas Exchange’?

A

The relationship between ventilation and blood flow in the lungs

5th edition published by Blackwell in 1990.

109
Q

What was the main finding of the study by West, Dollery, and Naimark in 1964?

A

Distribution of blood flow in isolated lung

Published in J Appl Physiol.

110
Q

Fill in the blank: The chapter on pulmonary edema and acute lung injury is found in _______.

A

Murray & Nadel’s Textbook of Respiratory Medicine

Lange Pulmonary Physiology, 10e (12 decks)

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