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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
What is hemoglobin?
A large protein molecule with four heme groups
25
Each heme group can pick up ____ molecule of oxygen
1
26
Why is oxygen extraction from hemoglobin 25%?
On average, one heme releases it's oxygen while the other three stay bound
27
Hemoglobin _________ to increase or decrease its affinity for oxygen
Changes its configuration
28
Oxygen dissociation depends on
2,3 - diphosphoglycerate CO2 tension Hydrogen ion concentration Temperature
29
2,3-DPG binds to deoxyhemoglobin, stabilizing the ___________, making it ________ for oxygen to bind
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
A right shift in the oxygen dissociation curve, _______ oxygen
Releases R for Release!
31
Hypoxia is defined as
<60 mmHg O2 in the blood
32
A decrease in temperature causes a higher O2 affinity because
Metabolic rates decrease
33
An increase in pH
Increases O2 affinity At a lower pH! more o2 is released to restore balance
34
5 categories of hypoxia
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
Oxygen is in the blood, but there is a. Problem with getting the blood circulated. This is an example of what kind of hypoxia?
Cardiac
36
Malignant hyperthermia is an example of what kind of hypoxia?
Demand
37
What is an example of hemic hypoxia?
Binding of hemoglobin to carbon monoxide
38
What is an example of histotoxic hypoxia?
Cyanide poisoning mitochondria ch disrupts ETC function
39
What are the methods of carbon dioxide transport?
Dissolved in plasma Bicarbonate (carbonic acid) Carbamino compounds (bound to proteins)
40
T or F. There is no good way to transport carbon dioxide in the blood.
True, carbon dioxide does not have a hemoglobin equivalent.
41
How is carbonic acid buffered with water in the blood?
Carbonic acid = [CO2 + H2O] [H + HCO3-] (bicarbonate)
42
How does the carbon dioxide dissociation curve compare to the oxygen dissociation curve?
It behaves more linearly
43
Removal of carbon dioxide from the blood is a self perpetuating cycle. What does this mean?
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
Describe the process of the chloride shift (hamburger shift)
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
What is the Haldane effect?
A property of hemoglobin to increase its affinity for carbon dioxide as blood is more deoxygenated
46
What is deoxygenated hemoglobin's affinity to CO2?
3.5x
47
Venous blood carries _______ carbon dioxide tha arterial blood
More
48
Large amounts of carbon dioxide is stored primarily as __________
Bicarbonate | About 120 L
49
How long does it cake to equilibriate an imbalance in carbon dioxide production or elimination.
20-30 min
50
What factors contribute to our control of breathing?
``` Respiratory rhythm generators Chemoreceptors Arterial PO2 Lung and airway receptors Vasal pulmonary stretch receptors ```
51
What are the respiratory rhythm generators?
Dorsal and ventral respiratory group on the brainstem
52
Group responsible for the rate of expiration
Ventral
53
Group responsible for the rate of inspiration
Dorsal
54
What do the chemoreceptors measure and where are they located?
Oxygen, carbon dioxide, acid state | Located at different parts of the arterial system
55
Chemoreceptors can be impacted by
Anesthesia | Pain
56
The hypercapnic drive is _______ than the hypoxic drive
Stronger
57
Examples of airway reflexes
Bronchospasm | Laryngospasm
58
What are the vagal pulmonary stretch receptors?
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
Extubation criteria
``` 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
Too many breaths causes inadequate
Tidal volumes | This is why RR < 30 for extubation
61
What is RSBI?
Rapid shallow breathing index | RSBI = RR/TV
62
A low RSBI indicates
Less effort to breathe

Physiology I for Anesthesia (7 decks)

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