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Physiology I for Anesthesia > 06 - Gas Transport Part 2 > Flashcards

06 - Gas Transport Part 2 Flashcards

0
Q

Absorptive atelectasis occurs when oxygen is not repleted in the alveoli because

A

The concentration of oxygen in the blood decreases as it is deceived to tissue and continues to diffuse from the alveoli

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1
Q

What two ways are oxygen delivered to the body once it is in the blood?

A

Dissolved in the blood itself

Bound to hemoglobin

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2
Q

The most efficient method of oxygen transport is

A

Bound to hemoglobin, the desired saturation is above 95%

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3
Q

What is alveolar oxygen tension?

A

The partial pressure of oxygen in the alveoli

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4
Q

Decreased alveolar tension causes decreased

A

Arterial oxygen tension and decreased available oxygen to bind

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5
Q

Hemoglobin saturation is critically dependent on

A

Oxygen tension

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6
Q

What is the oxygen content equation?

A

CaO2 = ([0.003 ml O2/dL blood/mmHg]PO2) + SaO2Hb*1.31 ml/dL blood)

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7
Q

How much more oxygen is bound to hemoglobin compared to oxygen dissolved in the blood?

A

About 60x more

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8
Q

What is mixed venous oxygen?

A

The amount of oxygen returned to the right side of the heart

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9
Q

T or F. The content of any venous blood sample from one patient is the same.

A

False, up until the blood perfuses the alveolar beds, any venous blood sample will have subtle differences in oxygen concentration

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10
Q

What is the normal saturation of mixed venous oxygen?

A

65-75%

25% of the oxygen has been utilized

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11
Q

What determines what the mixed venous oxygen is?

A

Oxygen saturation
Concentration of hemoglobin
Oxygen consumption
Cardiac output

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12
Q

People with anemia compensate by __________ and ___________ to maintain cardiac output.

A

Increased stroke volume and heart rate

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13
Q

How is oxygen delivery calculated?

A

Oxygen delivery = oxygen content * cardiac output

DO2 = caCO2 * CO

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14
Q

Oxygen delivery depends on

A

Cardiac output
Hemoglobin concentration
PaCO2

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15
Q

Why does cardiac output in an anesthetized patient increase?

A

They are more desaturated and compensate by increasing cardiac output until the heart itself becomes ischemic

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16
Q

How can oxygen consumption be calculated?

A

O2 consumption = CO * (CaO2 - CvO2)

This is the Fick Equation

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17
Q

Why doesn’t the body deliver oxygen at maximum cardiac output constantly?

A

Energy is wasted

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18
Q

If oxygen consumption is more than delivery, this is

A

Oxygen debt

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19
Q

Long term anaerobic metabolism leads to

A

Acidosis

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20
Q

What is normal oxygen consumption? CO?

A

O2 consumption = 250 ml/min
CO = 5000 ml/min (men)
4000-4500 ml/min (women)

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21
Q

What is low flow anesthesia?

A

Flow rates are decreased to save anesthetic gas and preserve temperature (less cold gas going into patient)

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22
Q

Does low flow anesthesia affect O2 consumption?

A

No, delivery and consumption we independent at low levels.

There is a direct relationship at high levels.

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23
Q

What makes up oxygen stores and what is the normal amount?

A

Bound to hemoglobin
Remaining in lungs
Dissolved in body fluids
1500 ml O2

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24
Q

What is hemoglobin?

A

A large protein molecule with four heme groups

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25
Q

Each heme group can pick up ____ molecule of oxygen

A

1

26
Q

Why is oxygen extraction from hemoglobin 25%?

A

On average, one heme releases it’s oxygen while the other three stay bound

27
Q

Hemoglobin _________ to increase or decrease its affinity for oxygen

A

Changes its configuration

28
Q

Oxygen dissociation depends on

A

2,3 - diphosphoglycerate
CO2 tension
Hydrogen ion concentration
Temperature

29
Q

2,3-DPG binds to deoxyhemoglobin, stabilizing the ___________, making it ________ for oxygen to bind

A

Low oxygen affinity state (T state)
Harder (allows for the stereostatic change)

The T state of hemoglobin has an opening in the center that 2,3 DPG easily binds to. This opening is absent in the R state.

30
Q

A right shift in the oxygen dissociation curve, _______ oxygen

A

Releases

R for Release!

31
Q

Hypoxia is defined as

A

<60 mmHg O2 in the blood

32
Q

A decrease in temperature causes a higher O2 affinity because

A

Metabolic rates decrease

33
Q

An increase in pH

A

Increases O2 affinity

At a lower pH! more o2 is released to restore balance

34
Q

5 categories of hypoxia

A

Hypoxic: 5 categories
Cardiac: low perfusion due to heart not functioning well
Hemic: low hemoglobin even with increased CO or deranged Hgb
Demand: increased consumption of O2
Histotoxic: O2 delivery and CO are adequate, but tissue can not use the oxygen

35
Q

Oxygen is in the blood, but there is a. Problem with getting the blood circulated. This is an example of what kind of hypoxia?

A

Cardiac

36
Q

Malignant hyperthermia is an example of what kind of hypoxia?

A

Demand

37
Q

What is an example of hemic hypoxia?

A

Binding of hemoglobin to carbon monoxide

38
Q

What is an example of histotoxic hypoxia?

A

Cyanide poisoning mitochondria ch disrupts ETC function

39
Q

What are the methods of carbon dioxide transport?

A

Dissolved in plasma
Bicarbonate (carbonic acid)
Carbamino compounds (bound to proteins)

40
Q

T or F. There is no good way to transport carbon dioxide in the blood.

A

True, carbon dioxide does not have a hemoglobin equivalent.

41
Q

How is carbonic acid buffered with water in the blood?

A

Carbonic acid = [CO2 + H2O] [H + HCO3-] (bicarbonate)

42
Q

How does the carbon dioxide dissociation curve compare to the oxygen dissociation curve?

A

It behaves more linearly

43
Q

Removal of carbon dioxide from the blood is a self perpetuating cycle. What does this mean?

A

In order to allow more carbon dioxide to enter a RBC to be converted to carbonic acid, carbon dioxide needs to be removed.
Adequate alveolar ventilation and perfusion are required

44
Q

Describe the process of the chloride shift (hamburger shift)

A

Carbon dioxide generated in the tissues diffuses into the capillaries and enters red blood cells. RBCs contain carbonic anhydride which converts the CO2 into carbonic acid. The carbonic acid dissociates to form hydrogen ions and bicarbonate. The fall of CO2 in the call allows more CO2 to enter the cell (self perpetuating cycle). Bicarbonate ions are exchanged for chloride (hydrogen ions can not cross the membrane). This bicarbonate export and chloride intake is referred to as the chloride shift.

45
Q

What is the Haldane effect?

A

A property of hemoglobin to increase its affinity for carbon dioxide as blood is more deoxygenated

46
Q

What is deoxygenated hemoglobin’s affinity to CO2?

A

3.5x

47
Q

Venous blood carries _______ carbon dioxide tha arterial blood

A

More

48
Q

Large amounts of carbon dioxide is stored primarily as __________

A

Bicarbonate

About 120 L

49
Q

How long does it cake to equilibriate an imbalance in carbon dioxide production or elimination.

A

20-30 min

50
Q

What factors contribute to our control of breathing?

A 
Respiratory rhythm generators
Chemoreceptors
Arterial PO2
Lung and airway receptors
Vasal pulmonary stretch receptors
51
Q

What are the respiratory rhythm generators?

A

Dorsal and ventral respiratory group on the brainstem

52
Q

Group responsible for the rate of expiration

A

Ventral

53
Q

Group responsible for the rate of inspiration

A

Dorsal

54
Q

What do the chemoreceptors measure and where are they located?

A

Oxygen, carbon dioxide, acid state

Located at different parts of the arterial system

55
Q

Chemoreceptors can be impacted by

A

Anesthesia

Pain

56
Q

The hypercapnic drive is _______ than the hypoxic drive

A

Stronger

57
Q

Examples of airway reflexes

A

Bronchospasm

Laryngospasm

58
Q

What are the vagal pulmonary stretch receptors?

A

Activation of these receptors helps to prevent over inflation of the lungs.
Inhibits the inspiratory area and the apneustic center, inhibiting the activation of inspiration. Allows expiration to begin.

59
Q

Extubation criteria

A 
TV > 5 cc/kg
VC > 10 cc/kg
Adequate motor strength
Neg inspiratory pressure < -25 cmH2O
PaO2 > 65 mmHg on FiO2 < 0.40
PaCO2 < 50 mmHg
RR < 30/min
TV/RR > 10
RSBI < 105
60
Q

Too many breaths causes inadequate

A

Tidal volumes

This is why RR < 30 for extubation

61
Q

What is RSBI?

A

Rapid shallow breathing index

RSBI = RR/TV

62
Q

A low RSBI indicates

A

Less effort to breathe

Physiology I for Anesthesia (7 decks)

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