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Physiology > Resp 3 > Flashcards

Resp 3 Flashcards

1
Q

Gases, just like ions and water, move

according to the principles of —

A

diffusion

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2
Q 
After gas 
exchange in the 
pulmonary 
capillaries,PO2 
is actually --- 
mmHg due to 
bronchial 
circulation
A

95

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3
Q

To calculate a partial pressure, you must
determine the — concentration of the gas
to other molecules

A

relative

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4
Q

Partial Pressure (Pgas) refers to the

A

pressure of one gas in

a mix.

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5
Q

Pgas =

A

PATM x Fractional Concentration of Gas

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6
Q 
Atmospheric Pressure (PATM) at sea level is --- mmHg and air is 
composed of --% nitrogen and --% oxygen (FiO2)
A

760
79
21

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7
Q

PN2 =

A

760 x 0.79 = 600 mmHg

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8
Q

PO2 =

A

760 x 0.21 = 160 mmHg

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9
Q

As air passes through the conducting zone of the lung, it is
humidified, creating a

A

partial (vapor) pressure for water (PH2O =
47 mmHg). This addition of water decrease) the partial pressure
of all other gases.

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10
Q

At normal alveolar ventilation and O2 absorption rates (250

ml/min), PAO2 is

A

100 mmHg. Increasing alveolar

ventilation will increase PAO2.

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11
Q

A gas within a liquid also exerts a —, designated in the same manner,
but calculated differently

A

partial

pressure

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12
Q

To calculate a partial pressure in a liquid solution, the

(2) are required

A

relative concentration and the solubility coefficient of the
gas

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13
Q

Solubility Coefficient.

A

Attractability of molecules to

water. If this number is high, the gas diffuses quickly.

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14
Q

Henry’s Law

A

Partial Pressure = Concentration of Dissolved Gas/(Solubility Coefficient)

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15
Q

is CO2 or O2 more soluble?

A

CO2 is more
soluble than
O2.

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16
Q

At a constant temperature, the amount of a gas that dissolves in liquid is directly proportional to the (2)

A

partial pressure and the solubility.

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17
Q

Conc. of Dissolved Gas=

A

Solubility Coefficient x Partial

Pressure

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18
Q

Gas Exchange at the Respiratory

Membrane Depends on (2)

A
  1. Transport rate through
    the respiratory membrane.
  2. The rate of alveolar
    ventilation
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19
Q 
An increase in alveolar 
ventilation will --- PAO2 and 
gas exchange with an upper 
limit of 150 mmHg (the PAO2 
of humidified air.
A

increase

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20
Q 
The  rate  of  gas  diffusion  across  the  respiratory  membrane 
depends on (5)
A
  1. Difference in Partial Pressures Across the Membrane (ΔP)
  2. Solubility of Gas in Fluid (S)
  3. Cross-Sectional Area of Membrane (A)
  4. Distance of Diffusion (d)
  5. Molecular Weight of Gas (MW)
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21
Q

Difference in Partial Pressures Across the Membrane (ΔP)

A

A tissue with high metabolic activity will have a
lower PO2, creating a larger partial pressure
gradient.

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22
Q

Solubility of Gas in Fluid (S)

A

CO2 is more soluble (S) than O2 so CO2 diffusion
more rapidly. This explains why there is rarely
ever a problem with CO2 exchange but often a
problem with adequately oxygenating blood.

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23
Q

Cross-Sectional Area of Membrane (A)

A

If more pulmonary capillaries are recruited, as in
exercise, the surface area (A) available for
diffusion increases (ex. converting Zone 2 into
Zone 3).

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24
Q

Distance of Diffusion (d)

A

If the thickness of the diffusion barrier increases
(d), such as with Pulmonary Fibrosis or Edema,
this decreases diffusion

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25
Q

V =

A

(ΔP x A x S)/(d x √MW)

V = Volume of gas
diffusing through the
tissue barrier per unit
time (ml/min)

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26
Q

Components of Respiratory Membrane: (6)

A
  1. Surfactant
  2. Alveolar Epithelium
  3. Alveolar Basement Membrane
  4. Interstitial Space
  5. Endothelial Basement Membrane
  6. Capillary Endothelium
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27
Q

Average width of respiratory membrane is

A

0.6 μm, 0.2 μm at slimmest

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28
Q

Under normal conditions, O2 transport into pulmonary
capillaries is —LIMITED, but under other
conditions (fibrosis, emphysema, strenuous exercise), it
can become —LIMITED.

A

PERFUSION

DIFFUSION

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29
Q

Diffusing Capacity of the Lung (DL)

Measures

A

respiratory membrane’s functional integrity

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30
Q

Measures respiratory membrane’s functional integrity

A

It is often useful to determine the diffusion characteristics of a patient’s lungs during their
assessment in the pulmonary function laboratory. It may be particularly important to
determine whether an apparent impairment in diffusion is a result of perfusion limitation or
diffusion limitation.

31
Q

Diffusing Capacity of the Lung (DL)

Amount of a

A

gas entering pulmonary blood per unit time
(ml/min/mmHg)
– Need to know the gas’s alveolar pressure, pulmonary capillary
pressure, and rate of uptake by the blood.

32
Q

Diffusing Capacity of the Lung (DL)
— cannot be calculated because of its rapid diffusion
and — is also difficult to calculate since most of O2 binds
to hemoglobin.

A

DLCO2

DLO2

33
Q

— is ideal for DL since it is diffusion-limited.

– Use diffusion coefficients to predict DL of other gases

A

Carbon monoxide

34
Q

Decreased Surface Area (A) or Increased
Distance of the diffusion barrier (d), will —
gas diffusion.

35
Q

What could an abnormally low DLCO test

indicate? (3)

A

Thickening of the Barrier
Decreased Surface Area
Decreased Uptake

36
Q

Thickening of the Barrier (increase d)

A

– Interstitial edema or fibrosis

37
Q

Decreased Surface Area (decrease A) (4)

A

– Emphysema
– Low Cardiac Output
– Tumors
– Ventilation-Perfusion Mismatch

38
Q

Decreased Uptake (2)

A

– Anemia
– Decreased blood volume in
pulmonary capillaries

39
Q

Someone with a thickened alveolar
membrane (pulmonary fibrosis) will
have (2)

A

diffusion limited oxygen transfer at
rest and it will be an even more
pronounced limitation with exercise.

40
Q

Calculation of PAO2 is important because you can compare

the value to —.

41
Q

Calculation of PAO2 is important because you can compare
the value to PaO2.
A large difference indicates

A

a problem with diffusion.

42
Q

Normal A-a gradient is — mmHg in a young, non-smoker.

The A-a gradient increases by — mmHg for each decade so a normal value for a 40 year-old would be — mmHg.

43
Q

You cannot easily measure —

44
Q

PAO2 is predicted based on: (3)

A
  1. The partial pressure of O2 inspired
  2. The PaCO2
  3. The ratio of CO2 produced/O2
    consumed—the respiratory quotient
45
Q

FiO2 is

A

the percentage of inspired oxygen (21%).

46
Q

Patm is

A

the ambient atmospheric pressure (760 mmHg at sea level).

47
Q

PH2O is

A

vapor pressure of water at 37°C and is equal to 47 mmHg.

48
Q

PaCO2 is

A

arterial CO2 levels (normal is 40 mmHg)

49
Q

Respiratory quotient (RQ) is

A

the ratio of CO2 produced (200 ml/min)
divided by the O2 consumed (250 ml/min), and its value is typically
0.8.

50
Q

The partial pressures of the gases

ONLY include the gases that are

A

dissolved in the plasma.

51
Q

If cells utilize more oxygen than
normal, the gradient —
which — flow of oxygen
from the blood to the tissues

A

increases

increases

52
Q

Tissue PO2 is a function of: (2)

A 
(1) The rate of O2 transport 
to the tissues in blood 
(blood flow)
(2) The rate at which the 
tissues use O2.
53
Q

Increased blood flow and/or
increased metabolism will
result in

A

more O2 delivery to

the tissues

54
Q 
Without Hemoglobin, CO 
would need to be --- L/min 
to transport sufficient oxygen 
to meet the needs of the 
tissues at rest.
55
Q

–% of total oxygen content is
dissolved in plasma (PaO2 =
100 mmHg)

56
Q

–% of O2 reversibly binds to
hemoglobin inside of the RBC
-does not contribute to partial
pressure

57
Q

Hemoglobin A (α2b2):

A

4 subunits
each of which each binds 1 O2
molecule.

58
Q

Iron must be in — state

to bind O2

A

ferrous (Fe2+)

59
Q

The amount of oxygen
bound to Hb
depends on: (2)

A
  1. Plasma PO2
  2. Number of binding
    sites in RBCs –
    depends on the Hb
    amount per RBC.
    (normally each
    RBC contains ~1
    million Hb
    molecules)
60
Q

CaO2 =

A

ml of O2 carried by oxyhemoglobin plus ml of O2

carried dissolved in plasma

61
Q

SaO2 is

A

the % saturation of hemoglobin

– Average 97%

62
Q

Hb represents

A

g of hemoglobin/100 ml blood

– Average is 15 g Hb/100 ml blood

63
Q

PaO2 is

A

the partial pressure of oxygen in arterial blood

– Average is 95 mmHg

64
Q

Average CaO2 is ~ — ml O2/ 100 ml blood

65
Q 
Reduction in the 
amount of hemoglobin 
in the blood 
significantly --- 
the blood oxygen 
content.
66
Q

2,3-BPG binds to Beta
subunits of deoxy HB
and

A

decreases its O2
affinity. It causes more
oxygen unloading.

67
Q

At a high PO2,
hemoglobin’s
affinity for O2 is
—.

68
Q

The lower the
PO2, the more
likely O2 will

A

dissociate from

hemoglobin

69
Q

Oxyhemoglobin Dissociation Curve

Shifts to the RIGHT (2)

A 
• Indicates  
DECREASED affinity 
between hemoglobin 
and oxygen
• In this instance, oxygen 
is MORE likely to 
dissociate from 
Hemoglobin.
70
Q

BOHR EFFECT

Helps match

A

O2 delivery to
O2 demand, advantageous
since O2 can be released at
selective tissues.

71
Q

RBCs contain 2,3-bisphosphoglycerate

A

– a metabolic intermediate. Levels of
2,3-BPG increase with exercise,
hypoxia from high altitude, pregnancy
and chronic lung disease.

72
Q 
Oxyhemoglobin Dissociation Curve Shifts to 
the LEFT (2)
A

• Indicates an INCREASED affinity between oxygen and
hemoglobin
• In this instance, oxygen is LESS likely to dissociate
from hemoglobin.

73
Q

Oxyhemoglobin Dissociation Curve Shifts to
the LEFT
causes (4)

A

– Decreased PCO2
– Increased pH (ex. 7.6)
– Decreased temperature
– Decreased 2,3-BPG

Physiology (53 decks)

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