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Physiology - Pulmonary > Gas Exchange and Transport > Flashcards

Gas Exchange and Transport Flashcards

1
Q

What governs the movement of gas between the liquid and gaseous environment?

A

Diffusion

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2
Q

Diffusion is responsible for movement of gas…

A

…near zero velocity environment of the alveolar sac

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3
Q

What is partial pressure?

A

The pressure of each individual gas in a mixture of gases.

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4
Q

What does Henry’s Law express?

A

Relationship between partial pressure and the amount of gas in a physical solution.

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5
Q

Henry’s law equation?

A

Concentration = (Solubility)(Partial Pressure)

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6
Q

What is the total gas pressure comprised of?

A

It is the sum of the partial pressures of each individual gas

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7
Q

Partial pressure is a good measure of tendency to ________

A

Diffuse

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8
Q

In a mixture gasses act as though they occupy ____% of the volume.

A

100%

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9
Q

Equation for partial pressure of a specific gas.

A

P = (Moles of X) (Total Pressure)

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10
Q

P-H2O in the lungs?

A

47 mmHg

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11
Q

Effects of additional water pressure in the lung?

A

Proportionally lowers the partial pressures of the other gasses.

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12
Q

Diffusion is inversely proportional to

Explain this in the context of a lighter gas

A

sqrt (MW)

Smaller gasses will achieve equilibrium faster

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13
Q

Determine the equation set up required for the diffusion ration of O2 (MW=32) and CO2 (MW=44)

A

Dif-Co2/Diff-O2 = sqrt[32/44]

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14
Q

Equ. for diffusion through liquid.

A

Diff-X/Diff-y = sqrt[(MW-Y)/MW-X)] X (solx/soly)

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15
Q

What is Fick’s Law of Diffusion all about?

A

Rate of Diffusion of Gas Across a Membrane

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16
Q

Equation for Fick’s Law of Diffusion.

A

Vol = [(Diffusion Coefficient)(Mem. Surface Area)(PP1-PP2)] / Membrane Thickness

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17
Q

Should you have Fick’s Law Memorize?

A

Sounds like yes.

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18
Q

In the respiratory system, conductance =

A

1/Resistance

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19
Q

Name three sources of Membrane resistance to diffusion to Oxygen.

A

Alveolar Capillary Interface
Plasma
Erythrocyte Membrane

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20
Q

Equation for Chemical Reaction Resistance.

A

1 / (O2 volume combining with hemoglobin/minute)(Pulmonary Capillary Volume)

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21
Q

What is Chemical Reaction Resistance?

A

The resistance to diffusion of O2 imposed by the chemical reaction of O2 with hemoglobin.

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22
Q

What is (o2 volume reacting with hemoglobin)(Pulmonary Cap. Volume) referring to?

A

Reaction rate of O2 and Hemoglobin for the Entire Lung

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23
Q

What is Diffusive Resistance?

A

Total Diffusive Resistance of the Lung

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24
Q

Equation for diffusive resistance?

A

Diffusive Resistance = Membrane Resistance + Chemical Reaction Resistance

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25
Q

Typically Membrane Resistance and Chemical Rxn Resistance are >, <, or =.

A

Approximately =

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26
Q

What might make Chemical Rxn Resistance much larger?

Why is this almost never a problem?

A

Hb saturation

O2 entering the lungs is far from saturated

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27
Q

Other than Oxygen, what compound may be influenced heavily by chemical resistance in the lungs.

A

CO2

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28
Q

How does exercise tend to influence the end capillary Po2?

A

It doesn’t typically, due to the built in safety factor

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29
Q

What happens with capillary Po2 at high altitudes?

A

With lower PO2, time for end capillary equilibration is prolonged (due to steep dissociation curve of hemoglobin.

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30
Q

How might thickening of the blood/gas barrier influence end capillary PO2?

A

End capillary PO2 may not reach alveolar

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31
Q

Express diffusion capacity in terms of Fick’s Law

A

Lung Diffusion Capacity = Rate of Diffusion/(Palv-Pcap)

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32
Q

What is the diffusion capacity….really?

A

The volume of gas moving per unit time for a given difference in PP of gas

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33
Q

Unit type used for diffusion capacity?

A

Conductance

1/Resistance

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34
Q

Relationship of diffusion capacity and Body Surface Area

A

Bigger Body = Bigger Diffusion capacity

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35
Q

Relationship of Diffusion capacity and training?

A

More training = recruitment of unused capillaries = Bigger Diffusion capacity

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36
Q

Relationship of Diffusion capacity and thickening of alv/cap membrane

A

Decreases

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37
Q

Relationship of Diffusion capacity and alv. surface area?

A

Decreases

Seen in Emphysema

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38
Q

Normal ph level?

A

7.35-7.45

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39
Q

Normal PA-O2?

A

80-10- mmHg

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40
Q

Normal Sa-O2?

A

95-100%

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41
Q

Normal Pa-CO2

A

35-45 mmHg

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42
Q

HCO3- conc?

A

22-26 meq/L

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43
Q

Pressure gradients move O2 through what pathway?

A

Inspired Air>Alveoli>Systemic arterial blood>tissues

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44
Q

Pressure gradiaents of CO2 through what pathway?

A

Tissues>Systemic Venous Blood>Alveoli>Expired Gas

45
Q

What causes difference in gas composition of inspired and alveolar air? (3)

A

Anatomic Dead Space (Incomplete Exchange)
Constant Absorption of O2, Secretion of CO2
Humidification decreasing PP of all gasses

46
Q

How much blood bypasses the pulmonary capillaries?

A

2-3%

47
Q

What gets around the pulmonary capillaries?

A

Blood in non-exchanging portions of the lungs

Coronary Venous Blood that goes straight to left ventricle

48
Q

What is the Ventilation/Perfusion Ratio (concept)?

A

Ratio of alveolar ventilation to alveolar blood flow

49
Q

Average V/Q ratio?

A

0.8

4L/min / 5L/min

50
Q

If an alveoli can’t open, what is the V/Q?

Physiological Shunt

A

Approx. 0

51
Q

If a lesion prevents any bloodflow to alveoli, what happens to V/q? (Physiological Dead Space)

A

Approaches infinity

52
Q

Two types of maladies that can cause ventilation perfusion mismatch.

A

Uneven Ventilation

Uneven Perfusion

53
Q

Ventilation is greatest at _____ and poorest at ____.

A

Base. Apex

54
Q

Why are ventilation changes seen across the lung?

A

The gradient of intrapleural pressure from apex to base.

55
Q

Alveoli in what part of lungs have greatest compliance? Why?

A

Base. Surfactant Effects

56
Q

Why do alveoli in the lungs have lower potential energy?

A

Relaxed elastic elements.

57
Q

How does gravity influence perfusion of the lung

A

Gravity increases hydrostatic pressure below the heart and decreases it below.

58
Q

Amount of O2 typically dissolved in blood.

So What?

A

0.29 ml/dl

Not enough to support life

59
Q

Where is the other 98.5% of oxygen in the blood?

A

Hemoglobin

60
Q

Why is there 25X more CO2 than O2 in the blood?

A

Higher solubility in water

61
Q

Weight of hemoglobin?

A

64.5k MW

62
Q

Basic molecular structure of hemoglobin?

A

4 subunits (2 alpha, 2 beta) with a polypeptide chain complexed with a heme

63
Q

What is a heme group?

A

A porphyrin ring with one ferrous iron atom

64
Q

What do heme groups do?

A

Reversibly binds O2 in an oxygenation reaction

65
Q

Can Fe3+ bind oxygen?

A

No

66
Q

How is the heme sandwich avoided?

A

Proximal Histidine binds Fe2+ and distal histidine (E7 prevents apposition of the second heme group.

67
Q

Who occupies the binding site in deoxyhemoglobin?

A

H+

68
Q

What does the property of cooperativity mean for hemoglobin?

A

Binding of one molecule of O2 facilitates the binding of other O2s

69
Q

Hill Plot logs values of ______ vs. _______

A

O2 combining with hemoglobin/1- (02 comb. with Hb)

Log PO2

70
Q

What is the slope of a Hill Plot Called? What does it represent?

A

Hill Coefficient

Cooperativity

71
Q

Approximate Hill Coefficient of Hb?

A

3 (So 3 cooperative binding sites)

72
Q

Give an example of an oxygen carrier with a Hill Coefficient of 1.

A

Myoglobin

73
Q

Increased CO2 shifts the dissociation curve…

A

Right

Decreasing affinity of O2 (Bohr Effect)

74
Q

What does the Haldane Effect say?

A

High PO2 results in dissociation of H+ and CO2 from Hb

75
Q

Mneumonic for Oxy dissociation curves?

A

CADET, Face Right

CO2, Acid, 2,3-DPG, Exercise and (Increased) Temperature

76
Q

What is BPG?

A

A highly anionic organic phosphate in fetal RBCs

77
Q

Why is it BPG in fetuses important?

A

It makes infant oxygen affinity greater than mom’s, so they can snag oxygen from her blood.

78
Q

Describe Salt Links in Deoxy Hb.

A
  1. Made from carboxy terminal amino acids.

Holds in “Tense Form”

79
Q

What happens to salt links in oxygenation?

A

Shifts alpha1 and beta2 subunits, breaking strong salt links for weaker ones.

Greater molecular movement. “Relaxed Form”

80
Q

Role of the porphyrin ring in cooperativity?

A

It is energetically difficult for the first O2 to get Fe2+ into a planar position.

Future broken salt bridges make later positioning easy

81
Q

The oxygen saturation curve is in a _______ shape.

A

Sigmoidal

82
Q

How does anemia influence O2 delivery?

A

It may be fine at high PO2 and fall dramatically as O2 saturation drops.

83
Q

Flattened Oxygen saturation relationship at high PO2 ensures…

A

..complete saturation despite wide PO2 variations.

84
Q

PO2 required in cells to sustain life?

A

30 mmHg

85
Q

Give an example of a time where the steep part of the SAturation/PP curve is a big deal

A

Exercise at high altitudes

You slide down the curve to way low O levels

86
Q

DPG is upregulated in ________

A

Poorly oxygenated erythrocytes

Right Shift –> Greater Delivery

87
Q

Two scenarios in which DPG upregulation is likely important?

A

High Altitude Living

Lung Disease

88
Q

How are carbamino compounds made?

A

Combination with Plasma Proteins

89
Q

The all-powerful CO2 in serum rxn

A

CO2+H2O H2CO3 H+ + HCO3-

90
Q

Why are bicarbonate generating reactions so slow in the blood?

A

No enzymes to catalyze them

91
Q

Review Dissolved CO2 equation on Page 8-17.

A

I don’t really know what to do with this.

92
Q

Form most CO2 takes in RBCs

A

Bicarbonate

93
Q

Enzyme that catalyzes the rxn of CO2+H2O?

A

Carbonic Anhydrase

94
Q

How does HCO3- get out of the RBC?

How is electroneutrality maintained?

A

Anion Exchanger

Cl- in for each HCO3- out

95
Q

Why is the hematocrit of venous blood higher than arterial?

A

Each CO2 adds an HCO3-/Cl-, triggering net movement of water into the cell

96
Q

Name two places carbonic anhydrase is found.

A

RBCs

Capillary Endothelium

97
Q

What does cap endo carbonic anhydrase do?

A

Facilitates Bicarbonate –> CO2 transition

98
Q

What do Hb molecules do with their extra H+ bound?

A

Upon oxygenation, liberate it to Convert HCO3- to CO2

99
Q

Two influences on the CO2-dissociation curve

A

Amount of Oxygenation

Haldane Effect

100
Q

With deoxygenation of tissues, Hb affinity for ____ increses.

A

CO2

101
Q

Pulmonary system has comparatively ____ pressure, _____ resistance, and ____ compliance

A

Low
Low
High

102
Q

Why are pressure, resistance, etc. diff in pulmonary?

A

Different Ventricle Thickness

Very little smooth muscle in arterioles

103
Q

Which circulation has lower mean capillary pressure?

A

Pulmonary

104
Q

What are extra-alveolar vessels?

A

Large extraparenchymal arteries/veins on the lung surface

Smaller arteries and veins in parenchyma

105
Q

Large extra-alveolar vessels are exposed to?

A

subatmospheric intrathoracic pressure

106
Q

Where are smaller extra-alveolar art/veins?

A

Tethered by connective tissue to alveoli (and thus expand with inflation)

107
Q

How is pulmonary vascular resistance lowered in exercise?

A

Distention of Microvessels

Recruitment of poorly perfused capillaries

108
Q

Why would a patient purse their lips in exhalation?

A

To increase airway resistance, thus improving airflow to lungs

109
Q

What to look for –

Post-partum woman, leg pain, high respirations, difficulty walking, cyanotic

A

Pulmonary Embolism

Physiology - Pulmonary (5 decks)

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