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Block 2 week 7 > Control of CO2 and O2 in alveoli and blood > Flashcards

Control of CO2 and O2 in alveoli and blood Flashcards

1
Q

Increase in PaCO2 in blood flowing to the medulla causes increase in (blank). What receptor allows for this?

A

ventilation

Central chemoreceptor in medulla

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2
Q

The peripheral chemoreceptors in carotid and aortic bodies have (blank) effect on the breathing of a normal person at rest at sea level.

A

little effect

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3
Q

When does peripheral chemoreceptors in carotid and aortic bodies begin to drive breathing?

A

when PaO2 falls below 60 mm HG and when lactic acid is released into the blood during strenuous exercise (lactate threshold)

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4
Q

What is the PCO2 ventilation equation?

A

PaCO2=(VCO2 X 0.863)/VA
VA=rate of alveolar ventilation by lung
VCO2= Rate of CO2 production metabolism

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5
Q

What is the alveolar gas equation oxygenation?

A

PAO2=PIO2-1.2(PaCO2)

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6
Q

Buildup of CO2 in the blood causes the pH to (blank)

A

fall

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7
Q

Buildup of CO2 in the blood causes the (blank) to fall

A

the PAO2

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8
Q

What are the two rates that control arterial CO2?

A 
metabolic production of CO2 (VCO2)
Alveolar ventilation (VA)
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9
Q

Buildup of CO2 in the blood is due to failure of some component of the (blank). (not an increase in metabolic CO2 production)

A

respiratory system

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10
Q

As you increase CO2 production, your ventilatory rate will (blank) to maintain your CO2

A

compensate

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11
Q

Alveolar ventilation and CO2 production double during moderate exercise in a 24-year old man. Describe the effect on PaCO2 this will have?

A

The PaCO2 will not changed

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12
Q

The terms hyper- and hypoventilation have nothing to do with patient’s (blank X 3)

A

respiratory rate, depth, or breathing effort!

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13
Q

Whether you are running around or sitting still your ventilatory rate will compensate so you will maintain your (blank) levels

A

CO2

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14
Q

What is the definition of hypercapnia?

A

greater than 45 mm Hg PaCO2 and you will be in hypoventilation

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15
Q

What is the definition of Eucapnia?

A

35-45 mm Hg and normal ventilation

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16
Q

What is the definition of Hypocapnia?

A

less than 35 mm Hg and hyperventilation

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17
Q

(blank) must be measured to assess a patient’s state of alveolar ventilation

A

PaCO2

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18
Q

An important clinical corollary of the PaCO2 equation is that we cannot reliably (blank) the adequacy of alveolar ventilation - and hence PaCO2 - at the bedside.

A

assess

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19
Q

What is the definition of hyperventilation?
What is the definition of hypoventilation?
What is the definition of Eucapnia?

A

less than 35 mm Hg
greater than 45 mm Hg
35-45 mm Hg

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20
Q

As PaCO2 increases pH falls if no compensation is present. As PaCO2 increases, PAO2 and PaO2 (blank), unless inspired O2 is supplemented.

A

fall

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21
Q

(blank) is a sign of advanced organ system impairment and is potentially dangerous. It results due to a failure of a component of the respiratory system.

A

Hypercapnia

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22
Q

The only physiologic reason for elevated PaCO2 is (blank) for the amount of CO2 produced and delivered to the lungs.

A

inadequate levels of alveolar ventilation

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23
Q

The rate of alveolar ventilation refers only to the alive volume of lung, dead spaces do not count, so what is the equation for alveolar ventilation?

A

VA (alive ventilation)= (VE) Total ventilation- (VD) dead space

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24
Q

How do you find total ventilation rate (VE)?

A

(breaths per min) X (tidal volume)

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25
Q

What is the space that is ventilated but not perfused called?

A 
dead space
(i.e. you will have gas entering and leaving but not blood flow and no gas exchange)
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26
Q

Alveolar space is called alive space because (blank) occurs here

A

gas exchange

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27
Q

What are the 2 types of dead space?

A

physiologic dead space and anatomic dead space

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28
Q

Alive alveoli that receive air, are perfused, and have gas exchanging, dead alveoli do what?

A

receive air but do not exchange gas

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29
Q

What is this?
All the airways that are ventilated but not perfused. Can never take part in gas exchange b/c of normal anatomy, ~150 ml
What is this?
anatomic + all other dead spaces

A

anatomic dead space

physiologic dead space (VD)

30
Q

What are the three processes required for gas exchange?

A
  1. gas entering and leaving
  2. blood flow= perfusion
  3. diffusion of gases across capilllary membrane
31
Q

(blank)= the total amount of air breathed per minute that is exposed to “live” alveoli

A

alveolar ventilation

32
Q

What happens when you have inadequate total ventilation (VE), or an increase in VD (lots of dead alveoli, or both?

A

hypercapnic

33
Q 
What do these do?
Massive obesity
Respiratory muscle weakness
Severe pulmonary fibrosis
Central nervous system depression
A

limit the rate or depth of breathing

34
Q

What is the minute ventilation requirement?

A

the level of VE (total ventilation) needed to keep PaCO2 constant

35
Q

When VD (ventilatory dead space) increases, minute ventilation requirement (blank).

A

increases

i.e. a rise in VE is needed to keep PaCO2 constant

36
Q

What is the minute ventilation requirement?

A

the level of VE (total ventilation) needed to keep PaCO2 constant

37
Q

When VD (ventilatory dead space) increases, minute ventilation requirement (blank).

A

increases

i.e. a rise in VE is needed to keep PaCO2 constant

38
Q

PaCO2 is elevated at (blank) mm Hg

39
Q

The PCO2 equation states that the only physiological reason for elevated PaCO2 is a level of (blank) inadequate for the amount of CO2 produced and delivered to the lungs.

A

inadequate alveolar ventilation

40
Q

(blank) is characterized by destruction of gas-exchanging air spaces, i.e., the respiratory bronchioles, alveolar ducts, and alveoli. Their walls become perforated and later obliterated with coalescence of small distinct air spaces into abnormal and much larger air spaces. V/Q goes (blank) .

A

Emphysema

up

41
Q

In a normal lung does PAO2 equal the PaO2?

A

no it does not!

42
Q

How do you find the partial pressure of a gas in air?

A

multiply the percentage of that gas in the air by the barometric pressure. i.e what is the PO2 of gas at sea level? A: .21 X 760 mm Hg= 159 mm Hg

43
Q

What is the partial pressure of oxygen in reno? How do you find the PIO2?

A

.21 X 680=143

(680-47)X.21

44
Q

What are these:
Region in which gas phase diffusion is so rapid that the PAO2 and PACO2 are uniform throughout the unit.
All alveolar ducts and their alveoli from proximal (first) respiratory bronchiole

A

Terminal Respiratory unit->physician’s working alveolus

45
Q

What is this:
Anatomic unit used by pathologists
10 to 12 terminal respiratory units

A

the acinus

46
Q

in the single alveolus, the PACO2 equals the (Blank) and the PAO2 equals the (blank)

A

PaCO2

PaO2

47
Q

In the terminal respiratory unit the Ave PAO2 (blank) the PaO2.

A

does not equal

48
Q

What does O2 expired equal?

A

=O2 inspired - O2 consumed by the body

49
Q

Is PAO2 and PIO2 and PaCO2 calculated or measured?

A

PAO2 and PIO2 is calculated

PaCO2 is measured

50
Q

What does PAO2 depend upon?

A

specific environmental conditions of the patient (i.e the PIO2)

51
Q

Is PAO2 and PIO2 and PaCO2 calculated or measured?

A

PAO2 and PIO2 is calculated

PaCO2 is measured

52
Q

Does PAco2 equal PaCO2?

Does PAO2 equal measured PaO2?

A

Yes

Yes at level of single alveolus, but at the level of the lung, terminal respiratory unit or patient then NO!

53
Q

PAO2 calculated from the alveolar gas equation is (blank) as the measured PaO2 from an ABG even in a healthy individual with no gas exchange problems

A

not the same

54
Q

PaO2 will always be (blank) than PAO2. What is a normal difference?

A

less

between 5 and 20 mm Hg

55
Q

What is the equation for normal PaO2?

A

Normal PaO2=100-(0.4 X age)

56
Q

What is the normal P(A-a)O2 difference?

A

Normal P(A-a)O2 difference = [Patient age / 4] + 4

57
Q

What is this?
Partial pressure of oxygen (PaO2) in the blood < normal for the subject’s age
It can also be defined as an oxygen content in the blood < normal for the subject’s age

58
Q

What is this?
Decreased oxygen supply to organs and tissues
Oxygen delivery to cells is insufficient for the demand
Does not require that the pO2 in the blood is low
But, can caused by hypoxemia.

59
Q 
What are these causes of?
Respiratory causes
Chronic obstructive pulmonary disease
Choking, asphyxiation, smoke inhalation, suffocation, carbon monoxide poisoning
Circulatory causes
Content of the blood
Cyanide toxicity
Accumulation of abnormal hemoglobin in blood
Anemia
Poor Blood Circulation
Very low blood pressure
Ischemic heart disease
Heart failure
Shock
60
Q

What are the three stages of diffusion of gases?

A

1) In the lung
2) Across the pulmonary capillary membrane and the RBC membrane
3) RBC interior to the Hb (O2) or from Hb to RBC interior (CO2)

61
Q

During inspiration what is happening in the conducting zone and the respiratory zone?

A

conducting zone-> gas is flowing

respiratory zone-> gas is diffusing passively

62
Q

What makes diffusion faster?

A

Large diffusing area (50-100 m)
High solubility of gas in barrier and blood
Large difference in gas partial pressures
-CO2 = 45-40 = 5
-PO2 = 100-40 = 60

63
Q

What makes diffusion slower?

A

Thicker barrier membrane
-Normal is ~ 0.3 µm
Gases with higher mass

64
Q

CO2 is (blank) times more soluble than O2

65
Q

In a fair fight, CO2 diffuses (blank) times faster than O2 across the alveolar membrane

66
Q

RBC capillary transit time is sufficient for (blank) to reach PAO2 under normal conditions

67
Q

capillary transit time is (blank) during exercise

68
Q

RBC capillary transit time is sufficient for blood to reach (blank) under normal conditions

69
Q

Is diffusion limited?

70
Q

Is perfusion limited?

71
Q

Diffusion is (blank) the process that limits the amount of O2 in the end capillary blood. Normally it is (blank) – the amount of gas taken up by the blood is limited by the amount of blood flow (not the rate of diffusion)

A

not normally

perfusion-limited

72
Q

What are these?
Severe exercise- capillary transit time is shortened
Pressure differences across membrane are lower (high alt)
Combination of the two

A

challenges to the diffusion of gases systems

Block 2 week 7 (9 decks)

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