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Pathophysiology Thorax > Modules #3: Respiratory Function > Flashcards

Modules #3: Respiratory Function Flashcards

1
Q

What drives gas exchange in the body?

A

driven by pressure gradients in both pulmonary capillaries and systemic capillaries

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2
Q

What is the PaO2 in the lungs?

A

PaO2 = 103 mmHg in the lungs

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3
Q

What is the PaO2 in blood returning from tissue?

A

as low as 40 mmHg

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4
Q

What is the PaO2 in blood leaving the pulmonary capillaries?

A

PaO2 = ~ 100 mmHg

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5
Q

What is the PaCO2 in the lungs?

A

PaCO2 = 40 mmHg

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6
Q

What is the PaCO2 in blood returning from tissue?

A

PaCO2 = 45 mmHg

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7
Q

What is the PaCO2 of blood leaving the pulmonary capillaries?

A

PaCO2 = ~ 40 mmHg

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8
Q

What is the PaO2 of tissues?

A

depending on metabolic demand, can be as low as 20 mmHg

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9
Q

What is the PaCO2 of tissues

A

depending on metabolic demand can be as high as 46 mmHg

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10
Q

What is pulmonary perfusion?

A

it is pulmonary circulation (blood flow)

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11
Q

How much is resting cardiac output (CO)?

A

5 L/min

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12
Q

How much is exercise cardiac output (CO)?

A

can increase up to 25 L/min

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13
Q

Describe the alveoli at the base of the lung

A

alveoli are smaller (and therefore have a reduced surface tension) which makes them easer to inflate

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14
Q

What are the alveoli @ the base responsible for?

A

normal tidal volume ventilation

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15
Q

Describe the alveoli at the apex of the lung

A

They’re larger (b/c they contain larger amount of residual air) which means they have an increased amount of surface tension = harder to inflate

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16
Q

What are the alveoli @ the apex responsible for?

A

ventilation during exercise

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17
Q

What is the pulmonary perfusion distribution dependent on?

A

Gravity

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18
Q

Does the base or apex have a greater amount of blood flow?

A

The base has a larger amount of blood flow

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19
Q

What happens when alveolar gas pressure exceeds capillary pressure?

A

the capillary collapses or is compressed

perfusion slows or stops

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20
Q

What happens as far as ventilation and perfusion at the 3 zones in upright lungs?

A

Zone I: alveolar pressure > arterial capillary pressure > venous capillary pressure –> perfusion is STOPPED by alveolar pressure

Zone II: arterial capillary pressure > alveolar pressure > venous capillary pressure –> perfusion = SLOWED DOWN by alveolar pressure

Zone III: arterial capillary pressure > venous capillary pressure > alveolar pressure –> perfusion is NOT EFFECTED by alveolar pressure

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21
Q

what is the V/Q ratio?

A

ratio of ventilation/perfusion

compares amount of air that enters alveoli/min w/ the amount of blood that travels through pulmonary capillaries/minute (Cardiac Output)

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22
Q

What is the V/Q ratio in the apex of the lung?

A

ventilation exceeds perfusion

this is a very small portion of the lung

23
Q

What is the V/Q ratio in the base of the lung?

A

perfusion exceeds ventilation

24
Q

What does V/Q measure clinically?

A

sum of V/Q from all zones

25
Q

What is normal V/Q at rest?

A

.8

Ventilation is lightly less than perfusion

See outline for explanation of calculation

26
Q

What is the V/Q during moderate exercise?

A

still @ .8

ventilation and respiration increase proportionately

27
Q

What is the V/Q during very intense exercise?

A

V/Q increases 5/1: ventilation = 100 L/min cardiac outut = 20 L/min

Ventilation increases way more than perfusion, meaning lungs aren’t limiting factor in exercise

28
Q

What happens to V/Q when blood flow is obstructed (i.e. pulmonary embolism?

A

V/Q will increase infinitely

29
Q

What happens to V/Q when ventilation is obstructed (i.e. COPD)

A

V/Q decreases

30
Q

What drives O2 transport across capillary membrane?

A

Drive by pressure gradients

31
Q

At rest how much time does it take RBC to travel through pulmonary capillary?

A

.75 seconds

32
Q

At rest how long does it take for for O2 to bind to hemoglobin (Hb)

A

.25 seconds

33
Q

What is the purpose of the oxyhemoglobin dissociation curve?

A

demonstrates oxygen saturation amounts @ different pressures

34
Q

What does the “flat” top portion of the oxyhemoglobin dissociation curve represent ?

A

buffer zone - 60 mmHg - 100 mmHg

increased O2 binding to Hb is maintained in this region

35
Q

What is happening at the “steep” portion of the oxyhemoglobin dissociation curve?

A

O2 doesn’t bind as well and will dissociate from hemoglobin

36
Q

What is happening with oxygen and hemoglobin in tissues?

A

Tissues are generally hypoxic (low PaO2) and will promote the release of O2 from hemoglobin so it can diffuse from blood stream into tissue

37
Q

Explain what is happening when the oxyhemoglobin dissociation curve has a “right shift” and what causes it.

A

there is a decreased affinity between hemoglobin and O2

elevated levels H+ (acidosis)

elevated levels of CO2 (hypercapnia)

38
Q

Explain what is happening when the oxyhemoglobin dissociation curve has a “left shift” and what causes it.

A

there is an increased affinity between hemoglobin and O2

low levels of H+ (alkalosis)

decreased CO2 levels (hypocapnia)

39
Q

What are the other 2 factors (besides H+ and CO2) that alters the oxyhemoglobin dissociation curve?

A

Body temperature

2,3 DPG levels

40
Q

What is the saturation of hemoglobin if PaO2 is 100 mmHg (like in the lung)?

A

Hb should be 98% saturated w/ O2

41
Q

What is the saturation of hemoglobin if PaO2 is 60 mmHg (right on the cusp of the flat portion of the curve?)

A

Hb should be 90% saturated w/ O2

42
Q

What is the saturation of hemoglobin If PaO2 is 40 mmHg (like what is typical of blood leaving exercising muscle)?

A

Hb should be 75% saturated w/ O2

43
Q

What does a pulse oximeter measure?

A

O2 saturation of arterial blood

44
Q

What is the normal pulse-ox values for healthy individuals?

A

95-97% saturated

45
Q

What is an acceptable pulse-ox values for pts suffering from pulmonary is eases like COPD?

A

90-90% saturated

46
Q

What is the threshold for “abnormal” pulse-ox values?

A

90%

47
Q

Whats the difference between the pressure gradient of CO2 and O2?

A

CO2 pressure gradient is much smaller

alveoli PaCO2 = 39-40 mmHg and pulmonary arteries/capillaries PaCO2 = 46 mmHg

48
Q

Name the 3 ways CO2 is transported throughout the body

A

dissolved in blood plasma

bound to hemoglobin (Hb)

transported in RBCs as bicaronate (HCO3-)

49
Q

How much of CO2 is dissolved in blood plasma?

A

5-10%

50
Q

How much of CO2 is bound to hemoglobin?

A

5-30%

51
Q

How much of CO2 is in bicarbonate form?

A

60-90%

52
Q

Describe the process of how CO2 forms bicarbonate

A

CO2 enters RBC

combines w/ H2O –> carbonic acid (H2CO3)

carbonic acid dissociated to form H+ + HCO3-

bicarbonate dissolves into blood plasma and RBCs buffer the H+

53
Q

What is the Bohr effect?

A

right shift of oxyhemoglobin dissociation curve

elevated CO2 decreases Hb - O2 affinity and promotes Hb - CO2 affinity

seen in tissues

54
Q

What is the Haladane effect?

A

left shift of oxyhemoglobin dissociation curve

elevated O2 values decreases Hb - CO2 affinity and promotes Hb - O2 affinity

seen in lungs

Pathophysiology Thorax (5 decks)

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