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FAll 2013 NAP Physiology > Respiratory Physiology > Flashcards

Respiratory Physiology Flashcards

1
Q

Name the 4 functions of the lung.

A

-prime function: gas exchange. Also metabolizes some compounds, filters unwanted materials from the circulation, and acts a resevoir for blood.

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2
Q

Oxygen and carbon dioxide are exchanged by what process?

A

simple diffusion, from high pressure to low pressure

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3
Q

What does Fick’s law state?

A

the amount of gas that moves across a sheet of tissue is proportional to the area of the sheet but inversely proportional to its thickness.

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4
Q

The conducting airways contain no _________ and therefore do not participate in gas exchange.

A

alveoli

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5
Q

Any part of the airway that does not participate in gas exchange is called?

A

dead space

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6
Q

What is the typical volume of normal anatomical dead space?

A

150mL

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7
Q

The terminal bronchioles divide into the ________ which have occasional alveoli budding from their walls.

A

respiratory bronchioles

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8
Q

Terminal bronchioles divide into respiratory bronchioles which then come to ___________ which are completely lined with alveoli.

A

alveolar ducts

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9
Q

The alveolated region of the lung where gas exchange occurs is known as the _____________.

A

respiratory zone.

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10
Q

The portion of the lung distal to the terminal bronchiole forms an anatomical unit called the:

A

acinus

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11
Q

The _________ zone makes up most of the lung, its volume being about 2.5 to 3 liters at rest.

A

respiratory

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12
Q

During inspiration the diaphragm _______ and the intercostal muscles _________ the ribs, thus increasing the cross-sectional area of the thorax.

A

descends; raise

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13
Q

Because the velocity of gas falls rapidly in the region of _____________, inhaled dust frequently settles out there.

A

terminal bronchioles

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14
Q

The airway is divided into 2 zones. They are:

A

conducting zone and respiratory zone.

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15
Q

Volume of the anatoic deadspace is about:_______mL.

A

150

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16
Q

Volume of the alveolar region is about ____ to ____ liters.

A

2.5-3

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17
Q

Gas movement in the alveolar region is chiefly by: _________

A

diffusion

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18
Q

The arteries, veins and bronchi run close together but toward the periphery of the lung what happens?

A

The veins move away to pass between the lobules, whereas the arteries and bronchi travel together down the center of the lobules.

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19
Q

The capillaries form a dense network in the walls of the ___________.

A

alveoli

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20
Q

The diameter of a capillary segment is about _________

A

7-10 micrometers, just large enough for a red blood cell.

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21
Q

The extreme thinness of the blood-gas barrier means that the capillaries are easily _________.

A

damaged

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22
Q

When damage occurs to the capillaries they______________

A

leak plasma and even RBCs into the alveolar space

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23
Q

The pulmonary artery receives __________ of the cardiac output.

A

100%

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24
Q

The resistance of the pulmonary circuit is (large/small)

A

very small

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25
Q

Each RBC spends about ____ seconds in the capillary network.

A

0.75 seconds. In this time it probably traverses 2-3 alveoli.

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26
Q

How is blood supplied to the conduction airways down to the terminal bronchioles.

A

By the bronchial circulation. This circulation is returned on the pulmonary vein to the L. atrium, thereby contributing a small amount of used, deoxygenated blood to be circulated to the body.

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27
Q

The blood/gas exchange area is (thick/thin)?

A

extremely thin. Only 0.2 -0.3 micrometers over much of its area.

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28
Q

The surface area of the blood/gas interface is (large/small)?

A

enormous. 50-100 meters squared.

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29
Q

The blood gas interface contains how many alveoli?

A

about 500 million

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30
Q

The blood gas interface is so thin that large changes in capillary pressure can___________.

A

damage the barrier.

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31
Q

Can the lung function without the bronchial circulation?

A

Yes. the bronchial circulation is a mere fraction of that through the pulmonary circulation. An example of someone living without this circulation is a lung tranplant recipient. The lung functions fairly well without it.

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32
Q

Because of the ________________ of the liquid lining the alveoli, relatively large forces develop that tend to __________ the lung.

A

surface tension; collapse.

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33
Q

The diameter of the capillaries is about:____________

A

7-10 micrometers

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34
Q

The thickness of much of the blood gas barrier is less than_________.

A

0.3 micrometers

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35
Q

Blood spends about ________ seconds in the capillaries/

A

0.75

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36
Q

Some of the cells lining the alveoli secrete_________, which dramatically lowers the surface tension of the alveolar lining.

A

surfactant

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37
Q

Large particles that try to enter the lungs are filtered out by:

A

the nose

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38
Q

Smaller particles that deposit in the conducting airways are removed by:

A

mucociliary escalator, a moving stairway of mucus that continually sweeps debris up to the epiglottis where it is swallowed.

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39
Q

The mucus of the mucociliary escalator is secreted by?

A

mucous glands and goblet cells in the bronchial walls

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40
Q

The mucociliary escalator moves rhythmically under normal conditions but are paralyzed by:

A

inhaled toxins (smokers)

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41
Q

How do the alveoli get rid of particles that reach them?

A

alveoli have no cilia so the particles are engulfed by large wandering cells called macrophages. The foreign material is then removed from the lungs by lymphatics or in the blood flow.

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42
Q

What is the advantage of having a thin blood gas barrier with a large surface area?

A

ideal for gas exchange by passive diffusion

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43
Q

The conducting airways extend to the terminal bronchioles, with a total volume of about _______mL. All the gas exchange occurs in the respiratory zone, which has a volume of about ____liters.

A

150 mL; 2.5-3 Liters

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44
Q

__________ flow takes inspired gas to about the terminal bronchioles; beyond this movement of gas is typically by:________

A

Convective flow; Diffusion in the alveolar region

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45
Q

When oxygen moves through the thin side of the blood-gas barrier from the alveolar gas to the hemoglobin it traverses what layers?

A

Surfactant; epithelial cell; interstitium; endothelial cell; plasma; red cell membrane

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46
Q

What is the Po2 in mmHg of moist inspired gas of a climber on the summit of Mt. Everest? (barometric pressure 247mmHg)

A

Po2= FiO2 x (pressure - vapor pressure) Po2= 0.21 x (247 -47 mmHg) Po2= 42 mmHg.

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47
Q

In the alveolar ducts, the predominant mode of gas flow is _________ rather than ________.

A

diffusion rather than convection

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48
Q

The functions of getting gas into and out of blood are carried out by what 3 functions?

A

ventilation, diffusion, and blood flow.

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49
Q

The amount of air inspired and expired in regular, relaxed breathing is the __________.

A

tidal volume

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50
Q

A maximal inspiration followed by a maximal expiration is the:_______ .

A

Vital Capacity

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51
Q

Even after maximum exhalation, some gas is left in the lung (it won’t deflate down to nothing). This volume is the ____________.

A

Residual volume

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52
Q

Ater a normal exhalation, the gas left in the lung is the ________________.

A

Functional Residual Capacity

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53
Q

Which three volumes cannot be measured with a simple spirometer?

A

Neither the functional residual capacity nor the residual volume nor the total lung capacity.

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54
Q

How can functional residual capacity and residual volume be measured if they cannot be read by spirometry?

A

Gas dilution technique. The patient inhales helium which is insoluble in the blood, after some breathes the helium in the lung with equalize with the amount being administered. Another way is by body plethysmograph, where the subject sits in an airtight box and pressure and volumes are measured as the patient breathes.

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55
Q

Do the body plethysmograph and the helium dilution method measure result in the same numbers?

A

No, body plethysmograph measures the total volume of gas in the lung, including any that is trapped behind closed airways. The helium dilution technique measures only communicating gas. or ventilated lung volume. (In a healthy patient, these numbers are virtually the same, but in someone with diseased lungs with air trapping, the numbers would be different)

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56
Q

Why is helium used in the gas dilution test?

A

Because of its low solubility in the blood.

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57
Q

The use of body plethysmograph depends on which gas law?

A

Boyles law.

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58
Q

What is the difference between total ventilation and alveolar ventilation?

A

total ventilation calculates the mL per breath x the RR. It gives the total amount of air leaving the lung each minute. However; because some is dead space, not all of that volume is available for gas exchange. Alveolar ventilation is more specific and accounts for the dead space.

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59
Q

What are the 4 stages of respiration?

A
  1. Ventilation- air into lung 2. Gas exchange from alveoli to pulmonary capillaries. 3. Gas transport from pulmonary capillaries to peripheral tissue capillaries 4. peripheral gas exchange from tissue capillaries into the cells.
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60
Q

Flow in the lungs is affected by ____________, _____________, and __________.

A

frictional reistance, shape of the conduit, and the nature of the gas

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61
Q

Bulk flow in the conducting apparatus occurs in response to _____________.

A

Pressure gradient

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62
Q

Flow, or __________ responds to a _____________.

A

volume over time; responds to a pressure gradient.

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63
Q

The high velocity conducting airways are the ______ and _______.

A

trachea and bronchi

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64
Q

The low velocity respiratory zone is comprised of __________ and ___________.

A

bronchioles and alveolar ducts.

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65
Q

As cross sectional area decreases, pressure gradient ________ and velocity of flow _______.

A

decreases; decreases

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66
Q

In the alveolus, O2 and CO2 move from air to blood by simple ________ in response to a _________ .

A

by simple diffusion in response to a pressure gradient. (Fick’s law)

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67
Q

Which gas is more diffusable CO2 or O2?

A

CO2

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68
Q

In a healthy person, does every RBC get exposed to oxygen in the capillary?

A

Yes, there is just enough room for one RBC to file through in a single file nature (everyone lines up to get a cookie)

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69
Q

How much more diffusable is CO2 than O2?

A

at least 20x. Think of a carbonated drink, how easily CO2 escapes. Even in a pathological state, CO2 will always be more diffusable.

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70
Q

What 2 types of cells line the alveolus?

A

Type 1 and Type 2 pneumocytes.

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71
Q

Which type of cells secrete surfactant?

A

Type 2 pneumocytes.

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72
Q

The pulmonary circulation is a (low/high) resistance circuit?

A

Low, pressures upon entering the circuit are low at about 12mmHg and go even lower as blood travels through, down to about 8 mmHg.

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73
Q

Name 4 factors that affect pulmonary circulation.

A
  1. the pressures around the alveolus 2. blood flow 3. The presence of vasoconstrictors or vasodilators. 4. Acid base status
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74
Q

What kinds of pressures affect the alveolus?

A

pressure in the alveolar vessels (on the alveolus themselves) and the extra alveolar vessel pressures from the vessels surround the alveolus.

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75
Q

Increased blood flow, or recruitment, as in the type that occurs with exercise causes a (decrease/increase) in resistance.

A

decreases resistance

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76
Q

Hypoxemia vasoconstricts or vasodilates the pulmonary vasculature?

A

vasconstricts. As oxygen supply decreases to a region of the lung, the vessels will constrict so that blood is shunted to a part of the lung that has more oxygen available for exchange.

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77
Q

Name 2 pulmonary vasodilators?

A

Nitric Oxide and Oxygen

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78
Q

How does acid base status affect vasodilation or constriction?

A

More alkaline blood will cause pulmonary vasodilation (So, Dr. N. runs the pH a little high in patients with pulmonary hypertension)

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79
Q

If you give inhaled Nitric Oxide to a patient, as treatment for pulmonary hypertension, what is the effect on systemic blood pressure?

A

Nil. Nitric oxide is bound to hemoglobin quickly and is inactivated within the pulmonary vasculature, so it won’t travel out to the rest of the body or have any effect on systemic BP.

80
Q

The perfect storm for efficient oxygen exchange occurs when lung volume is ________ and pulmonary resistance is ___________.

A

Optimal volume at low resistance. As you increase volume you will actually compress the vessels and less blood will be able to get through and be available for gas exchange.

81
Q

As the lung expands, what happens to extra alveolar vessels?

A

Alveoli are pulled apart, this expands extra-alveolar vessels and decreases resistance.

82
Q

At low lung volumes, extra alveolar resistance ___________ and alveolar or capillary vessel resistance ___________

A

Increases; decreases (not squashed)

83
Q

At high lung volumes, extra alveolar resistance _________ and alveolar or capillary vessel resistance _________.

A

decreases; increases (squashed)

84
Q

True or False, a Saline filled lung is easier to expand than an air filled lung.

A

True, because there is no air/fluid interface with surface tension

85
Q

As a healthy lung expands, surface tension __________.

A

increases

86
Q

As a healthy lung recoils back down, surface tension___________.

A

decreases. which prevents the alveoli from deflating completely and makes it easier to get that next breath in.

87
Q

Name the substance that keeps surface tension down at low lung volumes.

A

surfactant

88
Q

Surface tension occurs at :

A

air/ liquid interfaces

89
Q

Surfactant does 2 things. They are:

A

maintains stability, reduces surface tension at low lung volumes.

90
Q

What is the treatment for PPHN?

A

Inhaled Nitric Oxide

91
Q

How does inhaled nitric oxide work?

A

It diffuses into the pulmonary vascular bed, relaxing the pulmonary arteries.

92
Q

Name 5 non-respiratory functions of the lung.

A
  1. Defense- filter small particles 2. Metabolize vasoactive substances (produces angiotensin converting enzyme), 3. Metabolize bronchoactive substances (such as leukatreines- which causes bronchospasms) 3. Produces Immunoglobulins, especially IgA 4. Contain mast cells which contain Heparin.
93
Q

What do leukatrienes do in the lung?

A

cause bronchospasm

94
Q

What do mast cells do in the lung?

A

Produce heparin

95
Q

The key enzyme in salt and water homeostasis is?

A

ACE

96
Q

What is renin?

A

Renin is an enzyme secreted by the kidney that converts angiotensinogen (in the liver) to angiotensin I

97
Q

What is ACE?

A

ACE is an enzyme in the lungs that converts angiotensin I to angiotensin II.

98
Q

What 2 things does angiotensin II do to increase BP?

A

It constricts arterioles and expands the extracellular fluid

99
Q

As the lung expands, extra-alveolar vessels are pulled apart. This expands the extra-alveolar vessels and ____________resistance.

A

decreases

100
Q

What are some problems that might face a lung transplant recipient?

A

They will have a lack of ACE, a lack if IgA, a lack of mast cells (heparin) and difficulty metabolizing bronchoactive substances like leukotrines.

101
Q

Boyle’s law tells us that as ________ increases pressure decreases.

A

volume

102
Q

Is inspiration is active or passive?

A

active

103
Q

During inspiration the diaphragm moves down, the ribs move forward, upward and outward. This increases the lung volume. So pressure in side the lung must ___________

A

decrease

104
Q

When pressure in the lung decreases below atmospheric pressure a _________ is established and bulk air flow into the lung occurs.

A

gradient

105
Q

Is expiration active or passive?

A

Passive. Due to the elastic recoil of the chest

106
Q

As the chest wall volume decreases in exhalation, the pressure inside _____________.

A

increases

107
Q

Can expiration be an active process?

A

Yes, for example, when playing a wind instrument or in patients with asthma

108
Q

When expiration is active, what muscles are typically used?

A

abdominal, and internal intercostals.

109
Q

Bulk flow depends on 3 factors. They are:

A
  1. The size of the pressure gradient 2. The size and resistance of the conduit 3. The nature of the gas
110
Q

Describe the two types of flow.

A

Laminar: smooth, streamlined, fastest flow is through the midde. Turbulent: at branch points and asthma, or any state that creates increased resistance, the velocity of the gas slows down and increased pressure is needed to overcome it. Not smooth flow.

111
Q

Transitional flow occurs at:

A

branch points. Transition flow is turbulence not caused by a disease state but rather at normal transitional points in the airway.

112
Q

What is one manipulatable variable in turbulent air flow?

A

the density of the inspired gas. For example, heliox, which is low density, is used to treat airways obstructed by croup or asthma.

113
Q

What is heliox?

A

Heliox is a combination of 80 parts helium and 20 parts oxgyen.

114
Q

How does heliox work?

A

The low density heliox converts turbulent flow to laminar flow.

115
Q

Name 2 factors affecting airway resistance.

A

Generation of the airway and lung volume.

116
Q

Most airway resistance occurs up to the __________ generation.

A

7th

117
Q

The greater the lung volume the ________ the lung resistance.

A

lower

118
Q

How does bronchial smooth muscle affect airwary resistance?

A

If bronchial smooth muscle is contracted, airway resistance goes up.

119
Q

If beta 2 receptors are blocked, what happens to airway resistance?

A

resistance goes up

120
Q

Name two naturally occuring substances in the body that would block beta 2 receptors and cause bronchoconstriction.

A

acetylcholine and histamine

121
Q

Terbutaline and albuterol have what effect on beta 2 cells?

A

They are beta agonists that bronchodilate. They are used to treat asthma.

122
Q

Because of the effects of barometric pressure on the gas, the gas inhaled by deep sea divers has increased ________.

A

density

123
Q

The increased density of the gas breathed by deep see divers could cause ________ in the airway.

A

resistance, turbulent flow. Therefore divers often breathe some form of heliox to overcome this.

124
Q

Forced expiration, like pursed-lip breathing (increases/decreases) airwary resistance.

A

increases. They dynamic compression of the airways against the pursed lips causes an increase in airway resistance.

125
Q

In forced exhalation, pressure is built up in the airways up to a _________ point. At which point flow goes racing out like a waterfall effect.

A

Choke point

126
Q

Once you get past the choke point, what amount of the airflow is from the patients own effort?

A

None, once past the choke point, flow is effort indepedent.

127
Q

The term that describes a change in volume for a given change in pressure is:_________

A

compliance

128
Q

Elastic recoil of the lung occurs faster than the stretching of inhalation. Therefore the deflation curve on a volume pressure graph has a _________ slope.

A

steeper

129
Q

What are the effects of aging on lung compliance?

A

Like an old elastic band. Expands easily but does not recoil well. (increased compliance)

130
Q

What are the effects of asthma on lung compliance?

A

Breathing in is easy but it is difficult to breathe out against restricted airways. (higher compliance)

131
Q

What is the effect of fibrosis on lung compliance?

A

Fibrosis in the lungs scars the interstium and makes the lung both less stretchable and less able to recoil. decreased compliance.

132
Q

Does a lung with emphysema have increased or decreased compliance?

A

increased. Can breathe in easily but not out so well.

133
Q

Does a lung with pulmonary fibrosis have increased or decreased compliance.

A

decreased.

134
Q

Does a lung with alveolar edema have increased or decreased compliance?

A

decreased

135
Q

Does a lung with atelectalis have increased or decreased compliance?

A

decreased

136
Q

Does a hypoventilated lung (like with narcotics) have increased or decreased compliance?

A

decreased

137
Q

Does increased pulmonary venous pressure cause an increase or decrease in compliance?

A

decrease

138
Q

The elastic recoil of the lung tends to pull it inward but it is balanced by the ___________________ that counters that and balances it.

A

elastic recoil of the thoracic cage

139
Q

What is the volume of the lung that exists at the point where the elastic recoil of the lung pulling inwards and the elastic reoil of the thoracic cage pulling outward are balanced.

A

Functional residual capacity

140
Q

Name 2 good things the functional residual capacity does for us.

A
  1. keeps the lung open 2. acts as a bank to supply O2 when needed.
141
Q

By ‘keeping the lung open’, the functional residual capacity keeps _________ pressure negative.

A

intrapleural

142
Q

What effect does incentive spirometry have on functional residual capacity?

A

It maximizes FRC, preventing lung collapse

143
Q

Elastic recoil of the lung depends on _______ at the air-fluid interface of the alveoli.

A

surface tension

144
Q

Which cells produce surfactant?

A

Type 2 pneumocytes

145
Q

Name 5 effects surfactant has on the lungs.

A

1.It decreases surface tension at low lung volumes. 2.Increases compliance of the lung 3. Promotes stability of the alveoli 4.Keeps alveoli dry 5. Contributes to hysteresis

146
Q

What is hysteresis?

A

The difference in inflation and deflation volumes at a given pressure. The difference exists because of the air- water surface tension at the beginning of inhalation and because deflation is faster with the elastic recoil of the chest.

147
Q

Hysterisis would be less marked in a saline filled lung, why?

A

Because a fluid filled lung has no surfactant

148
Q

Surfactant _______ (increases/decreases) hysteresis.

A

decreases

149
Q

What are type 1 pneumocytes?

A

large, flattened, non-replicating cells involved in gas exchange.

150
Q

What happens when type 1 pneumocytes are damaged?

A

You get DAD (diffuse alveolar disease) as seen in SARS

151
Q

Type 2 cells can differentiate into ___________ if needed but ________________.

A

Type 1 but type 1 cannot differentiate into type 2s.

152
Q

Are ventilation and pefustion uniform throughout the lung?

A

No. They are non-uniformally distributed in the upright lung.

153
Q

Blood flow to the lung is _________ in the apex and ___________at the base because of gravitational effects.

A

lowest; highest

154
Q

Ventilation is _________ at the apex and ________ at the base.

A

Lowest; highest

155
Q

The V/Q ratio is ___________ at the apex and _________ at the base.

A

higher; lower

156
Q

Ventilation (increases/decreases) from the base to the apex of the lung in the upright position.

A

decreases

157
Q

_________ (apex/base) is aerated better at baseline because surrounding intrapleural pressure is more negative here.

A

Apex

158
Q

Per unit volume ventilation is (better/worse) at the base when compared to the apex.

A

better

159
Q

What is the partial pressure of O2 in the atmosphere?

A

Since O2 makes up 21% of our air, 21/100 x 760 mmHg = 149.73 or 150mmHg

160
Q

What does R represent in the alveolar gas equation?

A

R is the respiratory quotient. It represents the amount of CO2 generated per molecule of O2 utilized.

161
Q

What is the normal R value at basal metabolic rate?

A

0.8

162
Q

What is the normal value for PaO2 in a healthy lung?

A

95 mmHg for a healthy person breathing room air at sea level

163
Q

What is the alvelo- arterial gradient? What is the normal level?

A

The gradient that exists between the alveolar O2 and the arterial O2. PAO2- PaO2. Normal value is 5-10mmHg.

164
Q

Why would there by any difference ( the 5-10mm Hg accepted value) between the PAO2 and the PaO2?

A

because of physiological shunting. Some blood will enter the left heart without being oxygenated (ex. bronchial circulation) and this is ok at low levels.

165
Q

When would an increased Alveolar arterial gradient occur?

A

When there is a diffusion problem. As happens when the there is increased thickness in the wall or membrane.

166
Q

How do you calculate minute ventilation?

A

tidal volume x respiratory rate

167
Q

What are the 4 volumes of the lung?

A

Tidal volume, Residual Volume, Inspiratory reserve volume and expiratory reserve volume.

168
Q

What are the 4 capacities of the lungs?

A

Total lung capacity, vital capacity, inspiratory capacity and functional residual capacity.

169
Q

Which two capacities are essentially the same

A

FVC and VC

170
Q

Anything that involves measuring reserve capacites or volumes (can/ cannot) be measured by basic spirometery?

A

cannot

171
Q
A
172
Q

How can you measure anatomic dead space?

A

By Fowler’s method, which uses O2 to washout nitrogen.

173
Q

Physiological dead space contributes to the amount of CO2, true or false.

A

False. Gas in the dead space does not participate in gas exchange and therefore does not generate CO2.

174
Q

does PACO2 = PaCO2?

A

Yes, it should. CO2 is highly diffusable so arterial and alveolar CO2 will quickly reach equilibrium

175
Q

Tidal volume includes for both alveolar ventilation and dead space. True or False

A

True

176
Q

If alveolar ventilation is halved, what should happen to your PaCO2?

A

it is doubled

177
Q

Oxygen transfer from alveolus to artery is very efficient and is typically only limited by _____________.

A

Perfusion. or the number of RBCs available to pick up a molecule of O2.

178
Q

Which would be more likely to occur at high altitude, hypoxia or hypercarbia?

A

hypoxia. getting CO2 out is not the issue, getting O2 in is the issue.

179
Q

Which would be more likely to occur in interstitial lung disease, hypoxia or hypercarbia?

A

hypoxia. CO2 is more easily diffused so it will diffuse out a lot easier than oxygen will diffuse in.

180
Q

Which is more likely to occur in hypoventilaton, hypoxia or hypercarbia?

A

Hyerpcarbia. If you are breathing less there is more CO2 sitting in the alveolus. Passing blood CO2 will only diffuse out if a gradient exists.

181
Q

The transfer of CO is _________ limited.

A

diffusion

182
Q

CO is used to measure _________ capacity, which is decreased in interstitial lung fibrosis, sarcoidosis, or asbestosis

A

diffusion

183
Q

Hypoxemia: (Low O2 tension in arterial blood) could be caused by:

A

Low inspired O2, Hypoventilation, diffusion limitation, shunt, ventilation-perfusion mismatch.

184
Q

What sorts of things cause hypoventilation?

A

Drugs (morphine, barbiturates), damage to the chest wall, weakness of the respiratory muscles, increased resistance to airflow, as in deep sea diving.

185
Q

Does hypoventilation cause hypercarbia?

A

Yes, it always does.

186
Q

If pCO2 rises, what happens to alveolar O2?

A

it will decrease.

187
Q

Oxygen delivery to the tissues depends on __________.

A

perfusion

188
Q

Diffusion limitations can be overcome by increasing O2 only if_____________

A

the alveolus is adequately perfused

189
Q

How does increased PO2 in the alveolus increase the PO2 in the artery?

A

it increases the gradient

190
Q

What are 2 sources of physiological shunts?

A

bronchial and coronary circulation

191
Q

Name 4 common causes of pathological shunts?

A

AV malformations, ASDs, VSDs, PDAs.

192
Q

Does oxygen help treat a shunt?

A

No. it doesn’t matter how much O2 you put in the alveolus, if blood isn’t getting to it there will be no gas exchange.

193
Q

What happens to oxygen once it enters the blood?

A

Most of it is bound to hemoglobin but some of it will bubble around as free O2 in the blood exerting a partial pressure.

194
Q

___________ law helps us calculate how much O2 is carried in the blood in a dissolved state.

A

Henry’s

195
Q

Henry’s law states:

A

The amount of gas dissolved in a liquid is proportional to the partial pressure of the gas in the liquid.

196
Q
A

FAll 2013 NAP Physiology (2 decks)

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