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1 APEX > Respiratory - Airway Physiology > Flashcards

Respiratory - Airway Physiology Flashcards

1
Q

What is the conducting zone of the lungs?

A

anatomical dead space and does not participate in gas exchange

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2
Q

What is the respiratory zone of the lung?

A

where gas exchange takes place

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3
Q

Gas exchange can only occur in what type of tissue?

A

flat epithelium

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4
Q

What is the transitional zone of the lungs?

A

both an air conduit and allows some gas exchange

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5
Q

What anatomical structures make up the transitional zone of the lungs?

A

respiratory bronchioles and alveolar ducts

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6
Q

In order for gas exchange to occur, does pressure need to be greater inside or outside the lung?

A

pressure inside the airway needs to be greater than pressure outside the airway

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7
Q

What is pressure inside the lungs minus pressure outside the lungs called?

A

transpulmonary pressure TPP

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8
Q

What is pressure inside the lungs called?

A

alveolar pressure

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9
Q

What is pressure outside the lungs called?

A

intrapleural pressure

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10
Q

What is formula for TPP?

A

TPP = alveolar pressure - intrapleural pressure

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11
Q

What pressure is always positive to keep the lungs open?

A

TPP

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12
Q

What pressure is ways negative to keep the lungs inflated?

A

intrapleural

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13
Q

What instances causes intrapleural pressure to become positive? (2)

A

pneumo, forced expiration

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14
Q

When does alveolar pressure become positive? negative?

A

positive during expiration, negative during inspiration

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15
Q

During what phases of the respiratory cycle is there no airflow? (2)

A

FRC and end-expiration

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16
Q

What does contraction of inspiratory muscles do to thoracic pressure and thoracic volume?

A

decreases thoracic pressure, increases thoracic volume

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17
Q

What law explains the decrease in thoracic pressure, and increase in thoracic volume during inspiration?

A

Boyles

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18
Q

Contraction of what muscles are primarily responsible for inspiration? (2)

A

diaphragm and external intercostals

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19
Q

What are the accessory muscles of inspiration?

A

sternocleidomastoid ad scalene muscles

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20
Q

Is exhalation passive or active? How?

A

passive, recoil of chest wall

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21
Q

What muscles are responsible for forced exhalation? (TIREs)

A

transverse abdominus, internal oblique, rectus abdominis, external oblique

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22
Q

What muscles play a secondary role in active exhalation?

A

internal intercostals

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23
Q

What causes exhalation to become active?

A

increase in minute ventilation, lung disease, cough/clear secretions

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24
Q

What vital capacity is required to produce an effective cough?

A

15mL/kg

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25
Q

What is the process of exchanging gas between the atmosphere and the lungs, Oxygenation or ventilation?

A

ventilation

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26
Q

What are the two primary functions of ventilation?

A

acquire O2, remove CO2

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27
Q

Does the entire tidal volume participate in gas exchange? Why?

A

No, dead space.

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28
Q

What is the volume of dead space?

A

2mL/kg

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29
Q

What does increased dead space do to the PaCO2 - EtCO2 gradient?

A

widens the gradient and causes CO2 retention

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30
Q

What is the consequence of increased dead space?

A

more difficult to eliminate expired gas from the lungs

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31
Q

Where is anatomic dead space?

A

conducting airways (nose/mouth to terminal bronchioles)

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32
Q

What is physiologic dead space?

A

anatomic dead space and alveolar dead space

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33
Q

Do alveoli participate in dead space? How?

A

Yes, alveoli that are ventilated but not perfused

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34
Q

What is the formula for minute ventilation (VE)?

A 
VE = tidal volume x respiratory rate
VE = 500 x 10 = 5000mL/min
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35
Q

What is the fraction of VE that is available for gas exchange?

A

alveolar ventilation (VA)

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36
Q

What is the formula for VA?

A 
VA = (Vt - Vd) x RR
VA = (tidal volume - dead space) x respiratory rate
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37
Q

VA is directly proportional to what?

A

CO2 production

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38
Q

VA is indirectly proportional to what?

A

PaCO2

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39
Q

What is the Vd/Vt ratio?

A

fraction of tidal volume that contributes to dead space

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40
Q

Calculate the Vd/Vt for a 70kg patient spontaneously breathing a Vt of 0.45L

A

150mL / 450mL = 0.33

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41
Q

What affect does mechanical ventilation have on Vd/Vt ratio (increase or decrease)?

A

increase

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42
Q

Why does mechanical ventilation increase Vd/Vt ratio to 0.55?

A

increase alveolar pressure -> increases ventilation relative to perfusion

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43
Q

What is the most common cause of altered Vd under general anesthesia?

A

decreased cardiac output

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44
Q

How does a LMA affect dead space?

A

decreases Vd.

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45
Q

How does Atropine affect dead space?

A

Increases

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46
Q

How does atropine increase dead space?

A

bronchodilation increases the volume of the conducting airways

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47
Q

The table is being turned 180 during a craniotomy. You add extension tubing to your circle system. How is dead space affected? Why?

A

It isn’t! Anything proximal to the y piece does not affect dead space.

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48
Q

How can the circle system increase dead space?

A

faulty one way valve. The entire limb becomes dead space.

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49
Q

What equation is used to calculate physiologic dead space?

A

Bohr

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50
Q

What equation compares the partial pressure of CO2 in the blood vs partial pressure of CO2 in exhaled gas?

A

Bohr

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51
Q

What is the formula for the Bohr equation?

A

Vd/Vt = (PaCO2 - PeCO2) / PaCO2

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52
Q

What airway devices increase dead space? (3)

A

facemask, HME, PPV

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53
Q

What airway devices decrease dead space? (3)

A

ETT, LMA, trach

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54
Q

What drugs cause a decrease in dead space?

A

anticholinergics due to bronchodilation (atropine)

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55
Q

How does age affect dead space?

A

old age increases dead space

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56
Q

What does neck flexion and extension do to dead space?

A

extension increases

flexion decreases

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57
Q

What are the pathophysiologic causes of increased dead space?

A

decreased CO, decreased pulm. blood flow, COPD, PE (air, thrombus, amniotic fluid, bone)

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58
Q

What patient positions decrease dead space? Increase?

A

decrease - supine, head down

increase - sitting

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59
Q

What is the normal V/Q ratio?

A

0.8 (ventilation 4L/min, Perfusion 5L/min)

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60
Q

What two mechanisms affect distribution of blood flow to the lungs?

A

gravity and hydrostatic pressure

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61
Q

How are V/Q ratios affected by the upright position?

A

Higher V/Q ratio in the apex, Lower V/Q in the base of the lungs

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62
Q

In which portion of the lung are alveoli best and least ventilated?

A

best base, least apex

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63
Q

In which portion of the lung is perfusion the greatest?

A

base due to gravity

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64
Q

How is compliance calculated?

A

compliance = change in volume / change in pressure

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65
Q

Describe alveolar ventilation in non-dependent and dependent regions of the lung.

A

Non-dependent: low

Dependent: high

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66
Q

Describe perfusion in non-dependent and dependent regions of the lung.

A

Non-dependent: low

Dependent: high

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67
Q

Describe V/Q in non-dependent and dependent regions of the lung.

A

Non-dependent: high

Dependent: low

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68
Q

Describe PAO2 in non-dependent and dependent regions of the lung.

A

Non-dependent: high

Dependent: low

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69
Q

Describe PACO2 in non-dependent and dependent regions of the lung.

A

Non-dependent: low

Dependent: high

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70
Q

Describe PAN2 in non-dependent and dependent regions of the lung.

A

Non-dependent: same

Dependent: same

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71
Q

What does the balance of ventilation and perfusion throughout the lung determine?

A

PaO2 and PaCO2

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72
Q

Describe the relationship of V and Q in the most dependent area of the lung?

A

V < Q

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73
Q

Describe the relationship of V and Q in the nondependent area of the lung?

A

V > Q

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74
Q

What is the most common cause of hypoxemia in the PACU?

A

Atelectasis (V/Q mismatch)

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75
Q

How does anesthesia affect FRC?

A

FRC is smaller -> atelectasis

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76
Q

What are consequences of a smaller FRC in the PACU?

A

atelectasis, R-to-L shunt, V/Q mismatch, hypoxemia

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77
Q

How do you treat V/Q mismatch from atelectasis?

A

humidified O2, mobility, cough, deep breath, incentive spirometry

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78
Q

What West Lung Zone does mechanical ventilation increase?

A

increases zone 1

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79
Q

How is CO2 and O2 affected by underventilated alveoli?

A

blood retains CO2 and does not take enough O2

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80
Q

Does CO2 or O2 diffuse faster?

A

CO2 diffuses 20x faster

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81
Q

How is CO2 and O2 affected by overventilated alveoli?

A

excessive diffusion of CO2, unproportionate uptake of O2

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82
Q

What is the PAO2-PaO2 gradient with V/Q mismatch?

A

large

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83
Q

What is the PACO2-PaCO2 gradient with V/Q mismatch?

A

small

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84
Q

How does the body compensate for V/Q mismatch?

A

bronchioles constrict to minimize dead space (zone 1), hypoxic pulmonary vasoconstriction reduces blood flow to minimize shunt (zone 3)

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85
Q

What law describes the relationship between pressure, radius, and wall tension?

A

Law of Laplace

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86
Q

How do you calculate tension in a cylinder?

A

pressure x radius

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87
Q

How do you calculate tension in a sphere?

A

(pressure x radius) / 2

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88
Q

What type of cells produce surfactant? When does it start?

A

type 2, 22-26 weeks

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89
Q

What does surfactant do? (2)

A

reduces alveolar surface tension, prevents alveolar collapse

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90
Q

What happens to surface tension as alveolar radius changes?

A

stays constant

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91
Q

In each individual alveoli, V/Q ratio is determined by relative pressures between what? (4)

A

alveolus, arterial capillary, venous capillary, interstitial space.

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92
Q

What zone of the lung is described by: PA > Pa > Pv

A

zone 1

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93
Q

What increases zone 1? (4)

A

HoTN, PE, excessive airway pressure

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94
Q

Finish the sentence: in west zone 1, there is ___ but no ___.

A

there is ventilation but no perfusion

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95
Q

How does the body react to a increase in Zone 1?

A

bronchioles constrict to reduce dead space

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96
Q

What zone of the lung is described by: Pa > PA > Pv

A

zone 2

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97
Q

What is the V/Q ratio of zone 2?

A

V/Q = 1

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98
Q

What zone of the lung is described by: Pa > Pv > PA

A

zone 3

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99
Q

In zone 3 of the lung, blood flow is a function of what?

A

pulmonary arteriovenous pressure difference

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100
Q

In zone 3 most alveoli are better ___ than ____.

A

better perfused than ventilated (V < Q)

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101
Q

What is a shunt?

A

shunt is blood flow without perfusion

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102
Q

How does hypoxic pulmonary vasoconstriction react to a west lung zone 3?

A

reduces pulmonary blood flow to under-ventilated alveoli

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103
Q

Why should the PA catheter be placed in west lung zone 3?

A

pressure in the capillary is always higher than the alveoli, so the vessel is always open

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104
Q

What is an anatomic shunt?

A

any venous blood that directly empties into the left heart

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105
Q

Where are sites of normal anatomic shunt?

A

thesbian veins, bronchiolar veins, pleural veins

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106
Q

What zone of the lung is described by: Pa > Pist > Pv > PA

A

zone 4, pulmonary edema

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107
Q

What happens to lung pressure in pulmonary edema?

A

interstitial pressure exceeds pressure in the pulm. capillaries and alveoli d/t accumulation of fluid

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108
Q

What are the two causes of west zone 4?

A

increase in capillary hydrostatic pressure and reduction in pleural pressure

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109
Q

What causes an increase in capillary hydrostatic pressure leading to a west zone 4? (3)

A

fluid overload, mitral stenosis, pulmonary vasoconstriction

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110
Q

What causes a reduction in pleural pressure leading to a west zone 4? (2)

A

laryngospasm or inhalation against a closed glottis

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111
Q

Supplementing hypoventilation with O2 can lead to undetected ______.

A

hypercarbia

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112
Q

What equation determines the partial pressure of oxygen inside alveoli?

A

alveolar gas equation

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113
Q

How do you calculate alveolar oxygen?

A

PAO2 = FiO2 x (Pb - PH2O) - (PaCO2 / RQ)

= FiO2 x (760mmHg - 47mmHg) - (PaCO2 / 0.8)

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114
Q

What is a normal PAO2 value?

A

105.89 mmHg

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115
Q

What is the best way to treat hypercarbia?

A

increase alveolar ventilation and fix hypoxemia

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116
Q

How is the respiratory quotient (RQ) calculated?

A

CO2 production / O2 consumption

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117
Q

What is a normal RQ?

A

0.8

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118
Q

What causes a RQ > 1? RQ = 0.7?

A

RQ > 1 means overfeeding

RQ = 0.7 meas starvation

119
Q

What is the A-a gradient?

A

difference between alveolar oxygen PAO2 and arterial oxygen PaO2

120
Q

What does the A-a gradient help diagnose?

A

cause of hypoxemia

121
Q

What is a normal A-a gradient at room air?

A

less than 15 mmHg

122
Q 
Calculate the A-a gradient.
PAO2: 105
SaO2: 100
FiO2: 60
PaO2: 95
A

PAO2 - PaO2

105 - 95 = 10 mmHg

123
Q

What increases the A-a gradient? (4)

A

aging, vasodilators, R-to-L shunt, diffusion limitation

124
Q

What are examples of R-to-L shunts that would increase the A-a gradient?

A

atelectasis, pneumonia, bronchial intubation, intracardiac defect

125
Q

How is the percentage of a shunt estimated?

A

shunt increases 1% for every 20mmHg of a A-a gradient

126
Q

Are lung volumes based on total body weight, lean body weight, or ideal body weight?

A

ideal

127
Q

how do you estimate vital capacity?

A

60-70mL/kg

128
Q

How do you estimate FRC?

A

35mL/kg

129
Q

IRV + TV + ERV + RV = ???

A

total lung capacity

130
Q

IRV + TV + ERV = ???

A

vital capacity

131
Q

IRV + TV = ???

A

inspiratory capacity

132
Q

RV + ERV = ??

A

FRC

133
Q

RV + CV = ??

A

closing capacity

134
Q

what is the volume of total lung capacity?

A

5800

135
Q

what is the volume of vital capacity?

A

4500

136
Q

what is the volume of inspiratory capacity?

A

3500

137
Q

what is the volume of FRC?

A

2300

138
Q

what is the volume of IRV?

A

3000

139
Q

what is the tidal volume?

A

500

140
Q

what is the volume of expiratory reserve volume?

A

1100

141
Q

what is the volume of residual volume?

A

1200

142
Q

What is the amount of gas that can be forcibly exhaled after tidal inhalation?

A

IRV

143
Q

what is the amount of gas that enters and exits the lungs during tidal breathing?

A

tidal volume

144
Q

What is the volume of gas that can be forcibly exhaled after tidal exhalation?

A

ERV

145
Q

What is the volume of air that remains in the lungs after complete exhalation, reservoir during apnea?

A

residual volume

146
Q

What is the volume above residual volume where the small airways being to close?

A

closing capacity

147
Q

How does obstructive lung disease affect lung volumes?

A

increased residual volume and TLC

148
Q

Spirometry does not measure which lung volumes?

A

RV, TLC, FRC, closing volume, and closing capacity

149
Q

What is the reservoir of oxygen that prevents hypoxemia during apnea?

A

FRC

150
Q

What is static equilibrium?

A

at FRC the inward elastic recoil of the lungs is balanced by outward recoil of the chest wall

151
Q

How can FRC be indirectly measured?

A

nitrogen washout, helium wash in, body plethysmography

152
Q

What causes a reduction in FRC?

A

reduced outward lung expansion or reduced lung compliance (restrictive lung diseases), increased zone 3

153
Q

How does PEEP affect FRC?

A

restores FRC by reducing zone 3

154
Q

How does position, induction, NMB, and surgical displacement affect FRC?

A

Upright position < supine < anesthetic induction < NMB < surgical displacement

155
Q

How does general anesthesia affect FRC?

A

decreases

156
Q

What causes general anesthesia to decrease FRC?

A

diaphragm shifts cephalad 4cm d/t decreased inspiratory muscle tone and increased expiratory muscle tone

157
Q

How does obesity affect FRC?

A

decreases

158
Q

What causes obesity to decrease FRC?

A

decreased chest wall compliance, increased airway collapsibility

159
Q

How does pregnancy affect FRC?

A

decreases

160
Q

What causes pregnancy to decrease FRC?

A

diaphragm shifts up, decreased chest wall compliance

161
Q

Is FRC in neonates increased or decreased?

A

decreased

162
Q

What causes FRC in neonates to be decreased?

A

less alveoli, decreased compliance, ribcage prone to collapse

163
Q

How is FRC affected by old age?

A

increased

164
Q

What causes FRC to increase in old age?

A

decreased elastic lung tissue -> air trapping -> increased RV -> increased FRC

165
Q

What positions increase and decrease FRC?

A

Decrease: supine, lithotomy, trendelenburg
increase: prone, sitting, lateral

166
Q

How does paralysis affect FRC?

A

decreases

167
Q

What causes paralysis to decrease FRC?

A

diaphragm moves cephalad, decreased lung volumes

168
Q

How does inadequate anesthesia affect FRC?

A

decreases

169
Q

What causes inadequate anesthesia to decrease FRC?

A

Straining -> forceful expiration -> decreased ” lung volumes

170
Q

How does excessive IV fluids affect FRC?

A

decreases

171
Q

What causes excessive fluids to decrease FRC?

A

Fluid accumulation in dependent lung favors zone 3

172
Q

How does high FiO2 affect FRC?

A

decreases

173
Q

What causes high FiO2 to decrease FRC?

A

absorption atelectasis -> shunt

174
Q

What causes reduced pulmonary compliance to decrease FRC?

A

acute lung injury, pulm. edema, pulm. fibrosis, atelectasis, P-Effusion

175
Q

How does obstructive lung disease affect FRC?

A

increases

176
Q

What causes obstructive lung disease to increase FRC?

A

air trapping -> increased RV -> increases FRC

177
Q

How does PEEP affect FRC?

A

increases

178
Q

How do sigh breaths affect FRC? How?

A

increases by recruiting collapsed alveoli

179
Q

Describe closing volume?

A

during exhalation: the point where pleural pressure exceeds airway pressure

180
Q

In which zone of the lung do airways collapse first?

A

zone 3, dependent areas due to high pleural pressure

181
Q

What factors increased CV? (CLOSE-P)

A

COPD, LV failure, Obesity, Supine, Extremes of age, Pregnancy

182
Q

What is closing capacity?

A

sum of closing volume and residual volume

183
Q

The relationship between what two variables determines if airways collapse during tidal breathing?

A

FRC and CC

184
Q

What situation causes the airways to close during tidal breathing?
FRC > CC or FRC < CC

A

FRC < CC

185
Q

In a young healthy patient, airway closure occurs just above ____

A

residual volume

186
Q

How can we measure CV and CC?

A

washout of tracer gas (nitrogen or xenon-133)

187
Q

Where is CV and CC measured?

A

as patient exhales from total lung capacity

188
Q

What is oxygen content (CaO2)?

A

measure of how much O2 is present in 1 dL of blood.

189
Q

What are the two ways O2 is transported in the blood?

A

dissolved in plasma 3%, reversibly binds with Hgb 97%

190
Q

What is the formula for CaO2?

A

CaO2 = (1.34 x Hgb x SaO2) + (PaO2 x 0.003)

191
Q

What is a normal value of CaO2?

A

20mL O2/dL

192
Q

How is O2 dissolved in the plasma measured?

A

PaO2

193
Q

What law explains how oxygen is dissolved in the plasma?

A

Henrys

194
Q

What law states that the concentration of gas in solution is directly proportional to the partial pressure of the gas above the solution?

A

Henry

195
Q

How much oxygen does each gram of Hgb carry?

A

1.39mL

196
Q

What is normal Hgb and Hct in males?

A

Hgb 15g/dL, Hct 45%

197
Q

What is normal Hgb and Hct in females?

A

Hgb 13g/dL, Hct 39%

198
Q

How is DO2 calculated?

A

CaO2 x CO x 10

199
Q

What is a normal value of DO2?

A

1000 mL O2/min

200
Q

What is the difference between the amount of O2 that leaves the lungs and the amount that returns?

A

VO2 (O2 consumption)

201
Q

How is VO2 calculated?

A

VO2 = CO x (CaO2 - CvO2

202
Q

How does a left shift on the oxyhemoglobin curve affect affinity?

A

increased affinity (left love)

203
Q

How does a right shift on the oxyhemoglobin curve affect affinity?

A

decreased affinity (right release)

204
Q

How will changes in temperature shift the oxyhemoglobin curve?

A

decreased left

increased right

205
Q

How will changes in 2,3-DPG shift the oxyhemoglobin curve?

A

decreased left

increased right

206
Q

How will changes in CO2 shift the oxyhemoglobin curve?

A

decreased left

increased right

207
Q

How will changes in H+ shift the oxyhemoglobin curve?

A

decreased left

increased right

208
Q

How will changes in pH shift the oxyhemoglobin curve?

A

increased left

decreased right

209
Q

How will HgbMet, HgbCO, and Hgb F affect the oxyhemoglobin curve?

A

shift left

210
Q

At a SpO2 of 90%, PaO2 =

A

60

211
Q

At a SpO2 of 80%, PaO2 =

A

50

212
Q

At a SpO2 of 70%, PaO2 =

A

40

213
Q

What is P50 on the oxyhemoglobin curve?

A

PaO2 where 50% Hgb is saturated with O2

214
Q

Maximum O2 loading occurs at a PaO2 of what?

A

100mmHg

215
Q

What principle states that increased CO2 and decreased pH cause the erythrocyte to release O2?

A

Bohr effect

216
Q

How does hypoxia affect 2,3-DPG?

A

increases 2,3-DPG, right shift of curve

217
Q

How does banked blood affect the oxyhemoglobin curve?

A

banked blood has low 2,3-DPG -> left shift

218
Q

How is ATP produced in the body?

A

oxidation of proteins, carbohydrates, and fats

219
Q

Describe the phosphate bond.

A

high energy bond

220
Q

What is the primary substrate for ATP synthesis?

A

glucose

221
Q

What are the three key processes in glucose metabolism?

A

glycolysis, Krebs cycle, electron transport

222
Q

What is the primary goal of glycolysis?

A

convert 1 glucose into 2 pyruvic acid

223
Q

In the absence of oxygen, pyruvic acid is converted to what?

A

lactate

224
Q

Where does the Krebs cycle take place?

A

mitochondria matrix

225
Q

What is the primary goal of the glycolysis and the Krebs cycle?

A

liberate hydrogen from glucose

226
Q

What are the end products of oxidative phosphorylation?

A

CO2, water and 34 ATP

227
Q

What is the primary byproduct of aerobic metabolism?

A

CO2

228
Q

Is PvCO2 higher or lower than PaCO2?

A

PvCO2 is 5mmHg higher than PaCO2

229
Q

Is venous or arterial blood more acidic?

A

venous

230
Q

What are the three mechanisms of CO2 transport?

A

Bicarbonate 70%
bound to Hgb 23%
dissolved in plamsa 7%

231
Q

What ion is transported in erythrocytes to maintain electroneutrality?

A

chloride

232
Q

What physics principle states that oxygen causes the erythrocyte to release CO2?

A

Haldane effect

233
Q

Can venous or arterial blood carry more CO2 according to the Haldane effect?

A

venous blood can carry more

234
Q

What causes increased CO2 production? (7)

A

sepsis, overfeeding, MH, shivering, prolonged seizures, thyroid storm, burns

235
Q

What causes decrease CO2 elimination? (8)

A

Airway obstruction, increased dead space, increased Vd/Vt, ARDS, COPD, respiratory center depression, drug
overdose, inadequate NMB reversal

236
Q

What part(s) of the anesthesia machine can allow rebreathing of CO2?

A

incompetent one way valves, exhausted soda lime

237
Q

How does hypercapnia affect the oxyhemoglobin curve?

A

shifts right

238
Q

What affect does hypercapnia have on cardiac and smooth muscle?

A

myocardial depression and vasodilation

239
Q

How does hypercapnia affect the SNS?

A

increases SNS and increased catecholamine release

240
Q

How does hypercapnia affect minute ventilation?

A

increases

241
Q

How does hypercapnia affect potassium levels?

A

increases

242
Q

How does hypercapnia affect calcium levels?

A

Acidosis release Ca: increases inotropy

Alkalosis binds calcium: decreases inotropy

243
Q

How does hypercapnia affect ICP?

A

increases. CO2 diffuses across the BBB -> increased CBF and volume

244
Q

How does hypercapnia affect level of consciousness

A

decreases

245
Q

How does hypercarbia increase right ventricle workload?

A

CO2 causes vasoconstriction in the lungs causing pulm. HTN increasing RV workload

246
Q

How does a 10 mmHg increase in PaCO2 in acute respiratory acidosis affect pH?

A

decreases pH 0.08

247
Q

How does a 10 mmHg increase in PaCO2 in chronic respiratory acidosis affect pH?

A

decreases pH 0.03

248
Q

What is the relationship between PaCO2 and minute ventilation?

A

CO2 ventilatory response curve

249
Q

Where are chemoreceptors located?

A

medulla, carotid bodies, transverse aortic arch

250
Q

What do chemoreceptors monitor?

A

PaCO2

251
Q

At what levels is CO2 a respiratory depressant?

A

PaCO2 > 80-100

252
Q

What is MAC of CO2?

A

200mmHg

253
Q

A left shift and increased slope of the CO2 ventilatory response curve will create what ABG reading?

A

respiratory alkalosis

254
Q

A right shift and decreased slope of the CO2 ventilatory response curve will create what ABG reading?

A

respiratory acidosis

255
Q

What is the highest PaCO2 at which a person will not breathe?

A

apneic threshold

256
Q

How does a left shift on the CO2 ventilatory response curve affect the apneic threshold?

A

decrease

257
Q

How does a right shift on the CO2 ventilatory response curve affect the apneic threshold?

A

increases

258
Q

What causes a left shift on the CO2 ventilatory response curve?

A

hypoxemia, Met. acidosis, surgical stimulation, inter cranial HTN, salicylates, aminophylline, doxapram, NE

259
Q

What causes a right shift on the CO2 ventilatory response curve?

A

Met. alkalosis, CEA, sleep, volatiles, opioids, NMBs

260
Q

Where is the respiratory control center located?

A

medulla

261
Q

Where are central chemoreceptors located?

A

medulla

262
Q

Where are peripheral chemoreceptors located?

A

carotid bodies, and aortic arch

263
Q

What CN is responsible for lung stretch receptors?

A

CN 10

264
Q

What CN is responsible for peripheral chemoreceptors?

A

CN 9, 10

265
Q

What is the respiratory center that causes inspiration? Where is it located?

A

dorsal respiratory. Tractus solitarius of medulla

266
Q

What is the respiratory center that causes expiration? Where is it located?

A

ventral respiratory. Tractus solitarius of medulla

267
Q

When is the ventral respiratory center most active?

A

when exhalation demand increases

268
Q

What respiratory center inhibits the dorsal respiratory center? Where is it located?

A

pneumotaxic. upper pons

269
Q

What respiratory center stimulates the dorsal respiratory center? Where is it located?

A

Apneustic. Lower pons

270
Q

What is the function of the pneumotaxic center?

A

triggers the end of inspiration

271
Q

What is the function of the apneustic center?

A

causes inspiration

272
Q

What do central chemoreceptors respond to?

A

PaCO2

273
Q

What do peripheral chemoreceptors respond to?

A

PaO2

274
Q

Which chemicals free diffuse through the BBB and which do not?
CO2, H, HCO3

A

CO2 diffuses

H+ and HCO3 do not

275
Q

What is the most important stimulus for central chemoreceptors?

A

hydrogen concentration in the CSF

276
Q

As H+ concentration increases in the CSF what happens to the rate and depth of breathing?

A

rate and depth increase

277
Q

How long does it take HCO3 to equilibrate between the blood and CSF?

A

few hours, peaks in 2 days

278
Q

At a PaO2 < 60, the hypoxic ventilatory response closes oxygen-sensitive potassium channels in what cells?

A

type 1 glomus cells

279
Q

What does the hypoxic ventilatory response do to action potentials, calcium channels, and neurotransmitter release?

A

increase action potentials, opens Ca channels, and increases Ach and ATP release

280
Q

What nerves are responsible for the hypoxic ventilatory response?

A

Herings, and CN 9

281
Q

What conditions impair the hypoxic ventilatory response?

A

CEA and sub-anesthetic doses of inhalation and IV anesthetics

282
Q

What does not stimulate the hypoxic ventilatory response?

A

reduction in CaO2 in anemia and CO poisoning

283
Q

Stretch receptors in the lungs transmit information via which nerve to the dorsal respiratory center?

A

vagus nerve

284
Q

The dorsal respiratory center sends signals to the diaphragm via which nerve?

A

phrenic (C3-C5)

285
Q

What reflex turns off the dorsal respiratory center and and stops further inspiration?

A

Hering-Breuer

286
Q

What activates the Hering Breuer reflex?

A

lung inflation > 1.5L above the FRC (3x normal Vt)

287
Q

J receptor stimulation causes what type of breathing?

A

tachypnea

288
Q

What reflex causes the newborn to take their first breath?

A

paradoxical reflex of the head

289
Q

What reflex causes apnea, bradycardia, and vasoconstriction?

A

dive reflex (face submerged in cold water)

290
Q

What activates hypoxic pulmonary vasoconstriction?

A

reduced alveolar O2 tensions, PAO2

291
Q

What is the only region in the body that responds to hypoxia with vasoconstriction?

A

pulmonary vascular beds

292
Q

What drugs impair hypoxic pulmonary vasoconstriction?

A

volatile anesthetics > 1.5 MAC, vasodilators, PDE inhibitors, dobutamine, some CCB, phenylephrine, epinephrine, dopamine

293
Q

How does fluid status effect hypoxic pulmonary vasoconstriction?

A

Hypervolemia (LAP > 25) impair

Hypovolemia causes HPV

294
Q

What ventilator settings impair hypoxic pulmonary ventilation?

A

excessive PEEP and high tidal volume –> increased dead space

1 APEX (9 decks)

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