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Cardiovascular and Pulmonary > Pulmonary Physiology 3 > Flashcards

Pulmonary Physiology 3 Flashcards

1
Q

Diffuses much quicker than O2 but has a lower arteriole to vein gradient

A

CO2

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2
Q

Intense exercise reduces the time available for

A

Oxygenation

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3
Q

Exercise increases blood flow and thus decreases

A

Capillary transit time

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4
Q

In a healthy person with a normal environment, exercise will not change

A

PaO2

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5
Q

Exercise increases blood flow and reduces capillary transit time, normally this is not a problem unless there is a

A

Diffusion barrier or low PAO2 (hypoxia)

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6
Q

Under normal circumstances, PaO2 within the alveolar capillary reaches its maximum within approximately

A

0.25 seconds

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7
Q

This is explained by the fact that deoxy-Hb,sucha as what exists in venous RBCs has a high affinity for

A

O2

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8
Q

Once the O2 binding sites on Hb are saturated, we see an increase in

A

PaO2 (because PaO2 represents dissolved O2)

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9
Q

The alveolar-to-blood gas pressure gradient is the driving force for O2 diffusion from the

A

Alveolus

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10
Q

Once PaO2 is near 100 mmHg, a significant pressure gradient no longer exists and we see no further diffusion of O2 from the alveolus to the

A

Capillaries

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11
Q

During periods of increased cardiac output, blood moves through the capillaries more rapidly. This results in reduced

A

Perfusion limitation of O2 transfer

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12
Q

Because the rate of O2 diffusion is really fast and the formation of oxyhemoglobin occurs within 100ths of a second, the only limitation to oxygenation is the

A

Rate of capillary blood flow

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13
Q

The number of RBCs passing through a capillary per unit time

A

Rate of capillary blood flow

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14
Q

Keep in mind that in a healthy lung, total O2 transfer is elevated with increased cardiac output due to recruitment of previously non-perfused capillaries which augments the surface area for

A

O2 diffusion

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15
Q

Oxygen is carried in the blood in which two forms?

A
  1. ) Dissolved in plasma

2. ) Bound to Hb (SaO2)

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16
Q

Incorporates these variables plus the amount of Hb

A

Total blood O2 (CaO2)

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17
Q

The amount of gas dissolved in liquid is proportional to its partial pressure and temperature in equilibrium with

A

Gas

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18
Q

The higher the partial pressure of alveolar O2, the higher the

A

O2 in solution in blood

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19
Q

At normal body temperature (37 C) for each mmHg of PO2, there is

A

0.003 ml O2 / dl Blood

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20
Q

Thus at normal conditions, what is the mL O2 / dL blood?

A

0.3mL O2 / dL blood (dissolved O2)

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21
Q

Dissolved O2 can only meet a small portion of O2 demand, this is why it is critical that we have

A

Hb

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22
Q

A complex of Heme (iron porphyrin) with a protein globin

A

Hemoglobin

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23
Q

The oxygen binding capacity of Hb is

A

1.39 mL O2 / g Hb

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24
Q

Therefore under normal conditions, how much O2 can be carried in the arterial blood in the form of HbO2?

A

20.7 mL O2 / dL blood

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25
Q

Under normal conditions, the Hb is completely

A

Saturated

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26
Q

Oxygen saturation (SaO2) is commonly determined in the clinic with a pulse oximeter, which detects the color of

A

Hemoglobin

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27
Q

Non oxygenated Hb conformation appears

A

Purple (thus cyanosis is purple-blue)

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28
Q

Oxygenated Hb has which color?

A

Red

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29
Q

Saturation can also be used to determine concentration if you also know the

A

Concentration of Hb (usully 15g/dL)

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30
Q

If you know the O2 binding capacity and the concentration of Hb, PO2, and SaO2, you can calculate

A

O2 concentration

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31
Q

O2 concentration is proportional to PO2 in blood until

A

Hb binding sites are saturated

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32
Q

Upon saturation, the curve basically

A

Plateaus

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33
Q

In an O2 dissociation curve total CaO2 is primarily due to that complexed to

A

Hb

-dissolved O2 makes up only a small fraction

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34
Q

In an O2 dissociation curve at exceedingly low PO2, the O2 dissociation curve is

A

Less steep

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35
Q

In an O2 dissociation curve with increased PO2, the plot becomes steeper as

A

More O2 is bound to Hb (thus increasing the binding capacity)

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36
Q

In an O2 dissociation curve the steep portion of the curve represents

A

The ability of Hb to off-load O2 at the tissue level as well as up-load O2 at alveolar capillary level

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37
Q

In an O2 dissociation curve at normal PaO2, Hb is

A

100% saturated with O2. Increasing PO2 can not augment saturation

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38
Q

Note that normal arterial blood is represented on the

A

Upper, flat portion of the O2 dissociation curve

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39
Q

On the O2 dissociation curve, we can see that lowering PO2 to approximately 60-70 mmHg will

A

Not effect CaO2 (SaO2)

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40
Q

This phenomenon enables us to go to reasonably high altitudes and be exposed to other moderate hypoxic conditions without a significant loss in the ability to

A

Deliver O2 to tissues

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41
Q

The sigmoidal shape of the oxygen dissociation curve shows a rapid increase in blood O2 (oxyhemoglobin) with increased

A

PO2 (up to approximately 70 mmHg)

42
Q

After 70 mmHg, further increase in PO2 will not appreciably increase

A

O2 content

43
Q

The steep central portion of the sigmoidal curve shows that Hb will readily unload O2 at the level of peripheral tissues in response to a small drop in

A

Capillary PO2

44
Q

Moderate hypoxia or small decreases in ventilation and/or diffusion will not dramatically reduce

A

Oxygenation

45
Q

At a constant PO2, a shift in the O2 dissociation curve to the RIGHT shows that

A

Increased unloaidng of O2 from Hb will occur

46
Q

What 4 things will cause a rightward shift in the O2 dissociation curve, indicating a change of affinity of O2 for Hb?

A
  1. ) Reduced pH
  2. ) Increased PCO2
  3. ) Increased DPG (increased with hypoxia)
  4. ) Increased temperature
47
Q

At a constant PO2, a leftward shift in the dissociation curve signifies that

A

O2 has higher affinity for Hb (like in fetal circulation)

48
Q

CO2 is transported in the blood in which 3 forms?

A
  1. ) Dissolved
  2. ) Bicarbonate (HCO3-)
  3. ) Carbamino compounds
49
Q

Accounts for 10% of total CO2 expired by the lungs

-20x more soluble than O2

A

Dissolved CO2

50
Q

The reaction of H2O with CO2 to form H2CO3 and eventually HCO3- and H+ occurs in the

A

RBCs

51
Q

What percentage of CO2 blown off at the lungs is transported as HCO3-?

-Converted to CO2 upon reaching the lungs

A

60%

52
Q

Carbon dioxide that is combined with terminal amino groups of proteins, particularly Hb, are known as

A

Carbamino compounds

53
Q

Readily form in RBCs in the presence of CO2 and protonated deoxy-Hb

A

Carbamino compounds

54
Q

Carbamino compounds account for what percentage of expired CO2?

A

30%

55
Q

The dissociation of CO2 form Hb is affected by

-due to competitive binding sites on Hb

A

O2 sat

56
Q

The lower the PO2 and Hb binding, the greater the binding of

A

CO2 to Hb

57
Q

At the level of the alveolar-capillary unit, high PO2 induces

A

Dissociation of CO2 from Hb for expiration

58
Q

Enzymes, ligands, receptors, ion channels, transporters, and structural proteins are examples of molecules, the functions of which, will be affected by

A

Alterations in molecular charge

59
Q

The principal chemoreceptors

A

Carotid chemoreceptors

60
Q

Together, the peripheral chemoreceptors sense changes in

A

PCO2, pH, and PO2, with increased PCO2 as the main driving force

61
Q

As PCO2 rises even a couple of mm Hg above the normal range, receptor activity is increased sending afferent signals from the

  1. ) Aortic receptors via?
  2. ) Carotid receptors via?
A
  1. ) CN X

2. ) Hering’s Nerve

62
Q

Hering’s nerve essentially runs as a branch along

A

CN IX

63
Q

These afferents are wired into ventilatory regulatory centers within the

A

Medulla

64
Q

The peripheral chemoreceptors are more or less insensitive to changes in PO2 above approximately

A

50-60 mmHg

65
Q

Thus, the predominant driving force to increase ventilation is

A

Hypercapnia as opposed to hypoxemia

66
Q

Moderate decrease in PO2 will in fact induce an elevation in

A

Ventilation

67
Q

However, this effect is transient since the rapid expulsion of CO2 via increased ventilation raises

-counteracts increase in ventilation

A

pH

68
Q

Central chemoreceptors do not respond to

A

Hypoxemia

69
Q

Instead, these receptors are exclusively designed to sense elevated

A

PCO2 within CSF (most likely as increase [H+])

70
Q

The largest organ, the function of which is affected by fairly robust hydrostatic and pleural pressure gradients

A

The lung

71
Q

In order for gas exchange to occur, the alveoli must be sufficiently

A

Ventilated

72
Q

Importantly, alveoli ventilation (4-6 L/min) must also be matched with

A

Perfusion of alveoli

73
Q

In general, pulmonry blood flow (perfusion) is set by which 3 things?

A
  1. ) Local hydrostatic pressures
  2. ) Alveolar pressures
  3. ) Vascular resistance
74
Q

In general, ventilation is dependent on which 3 things?

A
  1. ) Pleural hydrostatic gradients
  2. ) Airway geometry
  3. ) Regional tissue compliances
75
Q

Equals the entire output of the right ventricle, which matches cardiac output

A

Pulmonry blood flow

76
Q

Consist of relatively thin walls when compared to those comprising the systemic vasculature

A

Pulmonary blood vessels

77
Q

This histologic feature is largely due to a low compliment of

A

Vascular smooth muscle

78
Q

Because of this, pulmonary vessels offer less resistance to

A

Flow

79
Q

Highly distensible and under relatively low pressure

A

Pulmonary Vessels

80
Q

The primary determinants of mean pulmonary artery pressure are

A

LA pressure, pulmonary blood flow, and pulmonary vascular resistance (PVR)

81
Q

Itself is affected by lung volume, alveolar and interpleural pressures, right ventricular output, and gravity

A

PVR

82
Q

The difference between the inside and outside pressures of a vessel

A

Transmural pressure gradient

83
Q

If there is a large pressure gradient, pulmonary vessel diameter will

A

Increase

84
Q

Will cause compression or collapse of a vessel

A

A negative transmural pressure

85
Q

With inspiration, the alveoli expand, this is combined with an elongation and reduction in diameter of

A

Alveolar capillaries

86
Q

This reduction in diameter causes an increased resistance to

A

Blood flow

87
Q

With expiration, alveoli collapse, this is combined with a shortening and increased in diameter of

A

Alveolar capillaries

88
Q

This increased diameter causes a decrease in resistance to

A

Blood flow

89
Q

Actually distend with inspiration and compress with exhalation

A

Large pulmonary arteries and veins

90
Q

An interesting phenomenon occurs during physical exertion whereby cardiac output can increase as much as 5-7x yet we do not see a correspondingly large increase in

A

Mean pulmonary arterial pressure

91
Q

This trait enables pulmonary vascular resistance to decrease with elevations in

-thus providing a greater matching of ventilation and perfusion

A

Pulmonary blood flow

92
Q

Pulmonary capillaries posses a high

A

Critical opening pressure

93
Q

That is, at resting cardiac output, when less ventilation is required, many of these vessels which surround less ventilated alveoli are

A

Constricted and relatively non-perfused

94
Q

However, with increased metabolic demand, increased flow due to increased cardiac output forces these vessels to

A

Open

95
Q

There is a regional distribution of

A

Pulmonary blood flow

96
Q

Pulmonary blood pressure increases towards the

A

Base of the lung

97
Q

This increased pressure recruits more vessels in this region to distend, allowing for

A

Disproportionately greater flow to base of the lung

98
Q

Lower blood pressures are present towards the

A

Apex of the lung

99
Q

Lower blood pressures are present outwards the apex of the lung, such that at rest, the critical opening pressure for these vessels is

A

Not achieved

100
Q

There are several factors which actively regulate

A

PVR

Cardiovascular and Pulmonary (25 decks)

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