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Systems Phys 2022 > Respiratory High Yield Concepts > Flashcards

Respiratory High Yield Concepts Flashcards

1
Q

The primary responsibility of the lungs is…

A

exchange gas

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2
Q

What processes must be functioning for optimal gas exchange?

A

Ventilation → getting gas to the alveoli

Perfusion → removing gas from the alveoli by the blood

Diffusion → getting gas across alveolar walls

Control of breathing → regulating gas exchange

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3
Q

The airways consist of…

A

a series of branching tubes which become narrower, shorter, and more numerous as they penetrate deeper into the lung

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4
Q

Conducting zone

A

no alveoli

trachea, bronchi, bronchioles

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5
Q

Respiratory Zone

A

alveoli

respiratory bronchioles. alveolar ducts and sacs

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6
Q

There are ___ alveoli in lungs creating a total surface area of about ___

A

300 million

75 m2

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7
Q

Define: Alveoli

A

small, thin-walled inflatable air sacs encircled by pulmonary capillaries

has a single layer of thin exchange epithelium and is the site of gas exchange

air flows between adjacent alveoli via pores of Kohn

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8
Q

What are the 3 types of cells in alveoli?

A

Type I alveolar cells

Type II alveolar cells

Alveolar macrophages

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9
Q

Define: Type I alveolar cells

A

very thin, allowing gas exchange

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10
Q

Define: Type II alveolar cells

A

thicker

secrete surfactant to ease lung expansion

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11
Q

Define: Alveolar Macrophages

A

protect and defend

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12
Q

Atmospheric Pressure (PB)

A

760 mmHg at sea level

decreases as altitude increases

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13
Q

Intra-alveolar pressure (PA)

A

will equilibrate with atmospheric pressure

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14
Q

Intrapleural Pressure (Pip)

A

756 mmHg

recoil forces create a vacuum (“-4”)

closed cavity

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15
Q

Transmural Pressure (PL)

A

pressure across the lungs (PA - Pip)

key to inflating lungs

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16
Q

___ and __ hold the lungs and thoracic wall in tight apposition even though the lungs are smaller

A

Intrapleural fluid’s cohesiveness and the transmural pressure gradient (most important)

PA = 760 mmHg, pushes out vs. Pip of 756 mmHg

PB = 760 mmHg, pushes in vs. Pip

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17
Q

Why does the pleural space have slightly negative pressure?

A

because the chest is pulling out, lungs are pulling in, and there’s no extra fluid to fill expanded space

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18
Q

Pneumothorax

A

air enters pleural cavity, pressure equalizes with atmospheric pressure, transmural pressure gradient is gone, lungs collapse, thoracic wall springs out

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19
Q

Boyle’s Law

A

describes the relationship between the pressure and volume of a gas

as volume decreases, pressure increases

P1V1 = P2V2

changes in volume of chest cavity during ventilation cause pressure gradients

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20
Q

An increase in chest volume causes..

A

a decrease in pressure

air moves into the lungs from the atmosphere

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21
Q

A decrease in chest volume causes…

A

an increase in pressure, air moves out from body

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22
Q

Inspiration results from…

A

the contraction of the diaphragm and intercostal muscles (an active process)

the rib cage swings upwards and outwards

the enlarged cavity housing the lungs undergoes a pressure reduction with respect to the pressure existing outside the body

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23
Q

Expiration results from…

A

the relaxation of the diaphragm and intercostal muscles (a passive process)

The rib cage moves inward and downwards

The elastic recoil of the lungs creates a higher intra-alveolar pressure compared to atmospheric pressure that forces air out of the lungs

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24
Q

Laminar Airflow

A

low flow rate

usually in small airways

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25
Q

Turbulent airflow

A

fast flow rate

usually in large airways

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26
Q

Why is the overall contribution to total R of bronchioles low?

A

even though each terminal bronchiole has a high resistance to flow, their total cross-sectional area is large and the tubes are in parallel so their overall contribution to total R is less low

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27
Q

Air flow in the respiratory system obeys the same rules as blood flow, what are they?

A

Airflow = ΔP/R

Flow increases as the pressure gradient increases and decreases as resistance increases

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28
Q

Where is airway resistance the greatest and how can it be measured?

A

airway resistance is greatest in the medium sized airways

it can be measured using Poiseuille’s Law: R = 8nL/πr4

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29
Q

What is the primary determinant of resistance in airways?

A

airway radius

the length and viscosity are virtually constant in respiratory systems

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30
Q

Why is the diameter of the bronchiole adjustable?

A

no cartilage but has smooth muscle

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31
Q

Low CO2 in the bronchiole leads to…

A

bronchoconstriction → increases resistance and decreases airflow

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32
Q

Increased CO2 in the bronchiole leads to…

A

bronchodilation → increases airflow

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33
Q

Define: Equal Pressure Point (EPP)

A

when airway pressure is equal to intrapleural pressure

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34
Q

Pulmonary Function Tests

A

measure lung volumes, lung capacities and flow rates

these tests can detect abnormalities in lung function before diseases become symptomatic

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35
Q

Air moved during breathing is divided into 4 lung volumes…

A

Tidal volume (VT)

Inspiratory reserve volume (IRV)

Expiratory reserve volume (ERV)

Residual volume (RV)

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36
Q

Tidal Volume (VT)

A

air volume moving in a single normal inspiration or expiration

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37
Q

Inspiratory Reserve Volume (IRV)

A

Additional volume inspired above tidal volume

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38
Q

Expiratory Reserve Volume (ERV)

A

air exhaled beyond the end of normal expiration

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39
Q

Residual Volume (RV)

A

air in respiratory system after maximal exhalation (not measured directly)

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40
Q

Vital Capacity (VC)

A

Maximum volume of air voluntarily moved through the respiratory system

IRV + ERV + VT = VC

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41
Q

Total Lung Capacity (TLC)

A

VC + RV = TLC

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42
Q

Inspiratory Capacity

A

VT + IRV = Inspiratory Capacity

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43
Q

Functional Residual Capacity (FRC)

A

ERV + RV = FRC

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44
Q

Obstructive Lung Disease

A

characterized by increases in lung volumes and airway resistance and decreases in expiratory flow rates (FEV1/FVC)

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45
Q

Emphysema

A

type of COPD

obstructive lung disease

characterized by increased lung compliance and decreased diffusion capacity for CO

condition in which elastin fibers are destroyed

high compliance and low elastance

exhibit poor recoil during expiration

can result in hyper-inflated lungs and “barrel-chest”

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46
Q

Restrictive Lung Diseases

A

characterized by decreases in lung volume, normal expiratory flow rates and resistance, and a marked decrease in lung compliance

more work must be expanded to stretch stiff lung

Possible Causes: inelastic scar tissue, insufficient surfactant production

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47
Q

Compliance

A

the ability of the lungs to stretch

defined by slope of pressure-volume curve for lungs → curve is steep at low and normal lung volumes but flattens at very high volumes

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48
Q

High-compliance lungs…

A

easily stretch

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49
Q

Low-compliance lungs…

A

require more force to stretch lungs (more work)

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50
Q

Hysteresis

A

different compliance for expiration and inspiration because of surfactant

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51
Q

What does elasticity mean for the lungs?

A

the lung is able to return to its original shape after the force stretching it has been removed

the normal lung is both compliant and elastic

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52
Q

What causes the ventilation difference in an upright lung? what are they?

A

ventilation differences are caused by the effects of gravity

alveoli at the apex are larger and less compliant and receive less of each tidal volume breath than alveoli in the base

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53
Q

Pulmonary elasticity is generated by:

A

Elastic fibers → the natural tendency of these fibers to recoil facilitates passive expiration

Surface tension → surface tension on the alveolar surface arises due to the strong attractive force that water has for itself → tends to make alveoli collapse, particularly smaller alveoli

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54
Q

Surfactant molecules ___ surface tension

A

reduce

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55
Q

The chest wall and lung are in equilibrium at the…

A

FRC

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56
Q

Respiratory Control is….

A

both automatic and voluntary

57
Q

Ventilatory control is composed of…

A

sensors, controllers, and effectors

58
Q

The Medullary Respiratory Center

A

the primary respiratory control center providing output to respiratory muscles

59
Q

Ventral Respiratory Group (VRG)

A

contains the rhythm generator whose output drives respiration

sets eupnea (12-15 breaths/min)

60
Q

Dorsal Respiratory Group (DRG)

A

Integrates peripheral sensory input (from chemoreceptors and stretch receptors) and modifies the rhythm generated by the VRG based on physiological need

61
Q

What are the two pontine centers? What do they do in general together?

A

Apneustic Center and pneumotaxic center exert a “fine tuning” effect on the medullary center to ensure smooth breathing and a smooth transition between inspiration and expiration

Pneumotaxic dominates

62
Q

Pneumotaxic center

A

sends impulses to DRG to turn off inspiratory neurons

dominates

63
Q

Apneustic Center

A

prevents inspiratory neurons from being turned off

64
Q

Central Chemoreceptors

A

near ventral surface of medulla

respond to PCO2 by sensing H+ in the medullary interstitial fluid

65
Q

Peripheral Chemoreceptors

A

carotid and aortic bodies

responds primarily to decreases in PO2, less so to decreases in pH and increases in PCO2

a drop in PaO2 below 60 mmHg results in an increased firing rate

only chemoreceptors to respond to changes in PO2

mechanism of detection ends in inhibition of a K+ channel

66
Q

The lungs have pulmonary receptors that are sensitive to…

A

lung volumes, mechanics, and irritants

67
Q

Pulmonary Stretch Receptors

A

located in airway smooth muscle

respond to mechanical stimulation and are activated by lung inflation

68
Q

What are pulmonary stretch receptors responsible for?

A

The Hering - Breuer reflex

when VT > 1 L pulmonary stretch receptors activated → APs travel to medullary center and inhibit inspiratory neurons

69
Q

Irritant Receptors

A

located between airway epithelial cells

stimulated by particles, cold air, touch or noxious substances (dust, smoke)

Protect by inducing cough or hypernea

70
Q

Juxta-capillary (J receptors)

A

in the alveolar capillary membrane

stimulated by distortion of the alveolar wall (lung congestion or edema)

71
Q

What is the most important regulator of ventilation at rest?

A

PCO2

72
Q

The sensitivity of the ventilatory response to CO2 is enhanced by…

A

hypoxia

73
Q

The sensitivity of the ventilatory response to O2 is enhanced by…

A

hypercapnia

74
Q

How is O2 carried in the blood from the lungs to the tissues?

A

Physically dissolved in the blood

chemically bound to Hemoglobin

75
Q

How is CO2 carried in the blood?

A

physically dissolved in the blood

chemically combined to blood proteins as carbamino compounds

as bicarbonate

76
Q

Gases (NO) with a rapid rate of air-to-blood equilibration are…

A

perfusion limited

77
Q

Gases (CO) with a slow air-to-blood equilibration rate are…

A

diffusion limited

78
Q

Under normal conditions, O2 transport is ___ but can be ___ in certain conditions

A

perfusion-limited

diffusion-limited

79
Q

Fick’s Law of Diffusion

A

The diffusion of gas across a sheet of tissue is directly related to the surface area of the tissue, the diffusion constant of the specific gas, and the partial pressure difference of the gas on each of the tissue and is inversely proportional to tissue thickness

Vgas ∝ (A*D*(P1-P2))/T

A = surface tension, D = diffsion constant (=Solubility/sqrtMW)

P1-P2 = partial pressure difference of gas one ach side of tissue

T = tissue thickness

80
Q

What is the relationship between O2 and CO2 loading and unloading?

A

they occur simultaneously and facilitate each other

81
Q

CO2 diffuses approximately __ times more rapidly through the alveolar-capillary membrane than O2

A

20X

82
Q

O2 binds ___ and ___ to the heme groups of the hemoglobin molecule

A

quickly and reversibly

83
Q

Dissolved form of O2

A

maintains its molecular structure and gaseous state

this is the form that is measured clinically in an arterial blood gas sample as the PaO2

84
Q

The ability of CO2 to alter the affinity of hemoglobin for O2 (Bohr effect)….

A

enhances O2 delivery to tissue and O2 uptake in the lungs

85
Q

Tissue hypoxia occurs when…

A

insufficient amounts of O2 are supplied to the tissue to carry out normal levels of aerobic metabolism

86
Q

The major source of CO2 production is…

A

in the mitochondria during aerobic cellular metabolism

87
Q

The reversible reaction of CO2 with H2O to form carbonic acid (H2CO3) with its subsequent dissociation to HCO3- and H+ is catalyzed by…

A

the enzyme carbonic anhydrase within RBCs

major pathway for HCO3- generation

88
Q

What is the shape of the O2 dissociation curve?

A

S - shaped

it is not linear

89
Q

What happens during the Plateau portion of the O2 dissociation curve?

A

the plateau area is above 60 mmHg

increasing the PO2 has only minimal effect on hemoglobin saturation → the same is true if there is a decrease in PO2 from 100 to 60 mmHg → this assures adequate hemoglobin saturation over a large range of PO2

90
Q

What does the steep portion of the O2 dissociation curve show?

A

20-60 mmHg

illustrates that during O2 deprivation (low PO2) O2 is readily released from hemoglobin with only small changes in PO2, which facilitates O2 diffusion to the tissue

91
Q

Pulmonary circulation is a ___ flow, ___ pressure, ___ resistance circuit

A

high flow (5 L/min)

low pressure

low resistance (1-2 mmHg/L/min)

92
Q

The lungs receive the entire volume of ___ cardiac output

A

Right ventricle (5 L/min)

93
Q

The average pressure in the pulmonary circulation is ___ compared to ___ systemic blood pressure

A

25/8 mmHg

120/80 mmHg

only need enough pressure to lift blood to top of lung

work required by right ventricle is much less than left ventricle

94
Q

Why doesn’t the right ventricle have to work as hard to overcome peripheral resistance?

A

the pulmonary arteries are much more compliant (distensible, easier to stretch) than the aorta and systemic arteries

the total length of pulmonary blood vessels is shorter

95
Q

What is the result of the right ventricle not having to work as hard to overcome peripheral resistance?

A

it allows for low pulmonary blood pressure → results in low net hydrostatic pressure → yields low fluid flow into interstitial space → lymphatic system removed filtered fluid

96
Q

Bronchial Circulation

A

supplies the conducting portions of the lungs

part of the systemic circulation → but the deoxygenated venous blood of the bronchial circulation does not return to the system circulation

97
Q

Where does the deoxygenated venous blood of the bronchial circulation go?

A

it flows into the pulmonary veins along with freshly oxygenated blood from the alveoli → the addition of deoxygenated blood slightly lowers the oxygen content of the blood before it reaches the left side of the heart

98
Q

Increases in CO or pulmonary artery pressure…

A

decrease pulmonary vascular resistance (PVR) and increase pulmonary blood flow by recruitment and distention of capillaries

99
Q

___ affect PVR

A

Changes in lung volume

100
Q

PVR is lowest…

A

at FRC

101
Q

Where are extra-alveolar vessels? When are they compressed?

A

they are tethered to surrounding alveoli and compressed with low lung volumes

102
Q

Where are alveolar vessels? When are they compressed?

A

they are located between alveoli and are compressed with high lung volumes

103
Q

What effect does Hypoxia have on PCR and pulmonary blood flow? What does it depend on?

A

Hypoxia can alter pulmonary blood flow and PVR depending upon whether it is regional or generalized

104
Q

The relationships among pulmonary artery, alveolar and pulmonary vein pressures divide the lung into 3 functional zones, what are they?

A

Zone 1: Pa< PA

Zone 2: Pa > PA > PV

Zone 3: Pa > PV > PA

105
Q

Functional Zone 1

A

Pa< PA

capillary collapses before it crosses alveolus

no flow

doesn’t exist in normal lungs (might with hemorrhage when BP and intravascular volume are low)

106
Q

Functional Zone 2

A

Pa > PA > PV

flow driven by difference between arterial and alveolar pressure

primary area of distention

recruitment of vessels during exercise

107
Q

Functional Zone 3

A

Pa > PV > PA

continuous forward flow through distended vessels

108
Q

Pulmonary capillary fluid exchange is regulated by…

A

the same Starling Forces as systemic capillaries, but also has surface tension and alveolar pressure influences

109
Q

Pulmonary Capillary Wedge Pressure (PCWP) measures…

A

back pressure from left atrium

110
Q

Normal PCWP is….

A

2-15 mmHg

111
Q

Increased PCWP indicates…

A

hydrostatic pressure and filtration forces

112
Q

The sum of the partial pressures of a gas must be equal to….

A

the total pressure

113
Q

The partial pressure of a gas is equal to…

A

the fraction of gas in the gas mixture times the total pressure

114
Q

By the time inspired gas reaches the trachea….

A

it is fully saturated with water vapor, which exerts a pressure of 47 mmHg at body temp and dilutes the partial pressures of N2 and O2

115
Q

The conducting airways do not participate in gas exchange, and therefore….

A

the partial pressures of O2, N2, and H2O vapor remain unchanged in the airways until the gas reaches the alveolus

116
Q

Minute (Total) Ventilation (VE)

A

Minute Ventilation (VE) = Tidal Volume (VT) (mL/breath) x respiratory rate (f) (breaths/min)

117
Q

Minute (Total) Ventilation (VE) at rest

A

6,000 mL = 500 x 12

exercise can increase 25-fold to 150 L/min

118
Q

When is VT more important than respiratory rate

A

when minute (total) ventilation increases

119
Q

Anatomical Dead Space

A

150 mL

volume of air filled in conducting airways incapable of gas exchange with blood = 150 mL

120
Q

Alveolar Ventilation (VA)

A

VA = (VT - VD) x f

VT = tidal volume, VD = dead space, f = respiratory rate

121
Q

Alveolar Ventilation (VA) at rest

A

4,200 mL = (500 - 150) x 12

122
Q

What effect does breathing deeply and slowly have on minute (total) ventilation (VE) and alveolar ventilation (VA)?

A

VE stays the same but VA increases

123
Q

What effect does breathing shallowly and rapidly have on minute (total) ventilation (VE) and alveolar ventilation (VA)?

A

VE stays the same but VA decreases (even to zero)

124
Q

Alveolar Gas equation

A

PAO2 = FIO2 (PB - PH2O) - (PACO2/R)

gives the partial pressure of oxygen in the alveolus

at sea level and when R = 0.8;

PAO2 = 0.21(760-47) - (40/0.8) = 100

125
Q

The respiratory quotient

A

the ratio of CO2 produced to O2 consumed

Mixed diet: 0.8

126
Q

The relationship between CO2 production and alveolar ventilation is defined by….

A

the PCO2 Equation

there is an inverse relationship between PACO2 and VA

127
Q

In normal individuals, the alveolar PACO2 is…

A

tightly regulated to remain constant at about 40 mmHg

128
Q

The V/Q ratio is the crucial factor in determining…

A

alveolar, and therefore, arterial PO2 and PCO2

129
Q

At the apex of the upright lung, alveoli are…

A

poorly ventilated and perfused, but they are better ventilated than perfused leading to high V/Q with a high PO2 and low PCO2

130
Q

When there is poor perfusion but good ventilation, alveolar gas pressure is…

A

similar to inspired air

PAO2 = 150

PACO2 = 0

131
Q

At the base of the upright lung, alveoli are…

A

well ventilated and perfused, but they are better perfused than ventilated leading to a low V/Q with a low PO2 and high PCO2

132
Q

When there is poor ventilation but good perfusion, alveolar gas pressure is….

A

similar to mixed venous blood

PAO2 = 40

PACO2 = 45

133
Q

A-a O2 Gradient

A

can be determined using the alveolar gas equation and arterial blood gases

measures gas exchange efficiency across alveolar - capillary membrane and can point to the cause of hypoxemia

134
Q

A normal A-a O2 Gradient is ___ and is due to…

A

≤20 mmHg

due to normal V/Q mismatch and shunting of bronchial and coronary blood into Thebesian veins back to left side of heart

135
Q

Normal A-a O2 Gradient can be predicted by

A

age/4+4

A-a O2 Gradient increases with age

136
Q

The five causes of hypoxemia are

A

low inspired O2

hypoventilation

diffusion limitation

right-to-left shunt

ventilation-perfusion mismatch

137
Q

The A-a O2 Gradient is normal if hypoxemia is due to…

A

low inspired O2 and hypoventilation

138
Q

The A-a O2 Gradient is widened if hypoxemia is due to…

A

diffusion defects, V/Q mismatch, and/or right-to-left shunt

139
Q

Right-to-left shunt is the only cause of hypoxemia in which arterial PO2…

A

fails to rise to the expected level when 100% O2 is administered

Systems Phys 2022 (25 decks)

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