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ventilation, oxygenation, respiration > ventilation, oxygenation, respiration > Flashcards

ventilation, oxygenation, respiration Flashcards

1
Q

A-a gradient equation

A

A-a = PAO2 - PaO2

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2
Q

what do you use to calculate the A-a gradient

A

alveolar gas equation and values from the arterial blood gas

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3
Q

the 5 main mechanisms of hypoxemia fall under what 2 main categories

A
  1. not enough oxygen getting into alveoli

2. not enough oxygen transferred into the capillary bed

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4
Q

with not enough oxygen getting into the alveoli, what is the A-a gradient

A

normal A-a gradient

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5
Q

with not enough oxygen transferred into the capillary, what is the A-a gradient

A

elevated A-a

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6
Q

what causes not enough oxygen getting into the alveoli

A
  • low atmospheric pressure (ex high altitude)

- hypoventilation (ex heroin overdose)

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7
Q

what causes not enough oxygen transferred into the capillary blood

A
  • ventilation-perfusion mismatch (ex atelectasis)
  • right to left shunting (ex atrial septal defect)
  • diffusion defects (ex pneumonia)
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8
Q

pulmonary ventilation

A

inflow and out flow of air b/w the atmosphere and lung aveoli

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9
Q

external respiration

A

diffusion of oxygen and carbon dioxide between the aveoli and the blood

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10
Q

internal respiration

A

transport of O2 and CO2 in the blood and body fluids to and from the body’s tissue and cells

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11
Q

what systems regulate ventilation and respiration?

A

CNS effects and Peripheral effects

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12
Q

lungs can be expanded and contracted in 2 ways. what are they?

A
  1. downward and upward movement of diaphragm (normal quiet breathing)
  2. elevation and depression of chest cavity (increase thoracic volume by 20%)
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13
Q

what are the 3 pressures that cause the movement of air in and out of the lungs

A

pleural
alveolar
trans pulmonary

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14
Q

what is pleural pressure

A

pressure of the fluid in the thin space between the lung pleura and chest wall pleura

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15
Q

what is another name for pleural pressure

A

intrapleural pressure

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16
Q

at rest, what is the pleural pressure

A

-5 cm H2O

which is negative suction

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17
Q

what is the pleural pressure during inspiration

A

increases to -7 cm H2O

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18
Q

what is alveolar pressure

A

pressure inside the lung alveoli

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19
Q

what is another name for alveolar pressure

A

intrapulmonary pressure

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20
Q

when is the alveolar pressure 0 cm H2O

A

when glottis is open and no air is moving the alveolar pressure

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21
Q

During inspiration, what is the alveolar pressure?

A

decreases to -1 cm H2O and 0.5 liters of air enters in 2 seconds

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22
Q

during experation, what is the alveolar pressure

A

alveolar pressure increases to +1 cm H2O and forces 0.5 liters of air out of lung

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23
Q

transpulmonary pressure is also known as “___ ____ pressure” which measures….

A

Elastic recoil pressure

the measure of the elastic force in the lungs

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24
Q

Pulmonary blood flow represents ____ and is usually the blood flow measured to determine ____ via the Swan Ganz catheter

A

represents total cardiac output and usually the blood flow measured to determine total cardiac output via the Swan Ganz catheter

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25
Q

at rest, the entire blood volume of the body passes through the ….

A

pulmonary circulation every 1 to 2 minutes and more frequently during exercise

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26
Q

in an adult at rest, the capillary blood volume is about how much and what does it approximate?

A

capillary blood volume is 140-200 ml

approximates the right heart stroke volume

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27
Q

The lung has dual circulation. what are the 2 circulations?

A

pulmonary circulation and bronchial circulation

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28
Q

what kind of vasculature is pulmonary circulation and what is it involved in?

A

a low-pressure, high-volume vasculature

involved in gas exchange that perfuses alveoli

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29
Q

what is bronchial circulation and what does it provide?

A

a high-pressure, low volume system

provides nutrients and gas exchange for the bronchial tree and conducting airways

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30
Q

Bronchial circulation is part of the ___ ____ and receives about 2% of the CO from the ___ ____

A

part of the systemic circulation and receives about 2% of the total CO from the left ventricles

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31
Q

where do the bronchial arteries arise from?

A

branches of the aorta, intercostal subclavian, or internal mammary arteries

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32
Q

how much does bronchial veins drain and from where?

A

about 1/3 of the venous drainage from the bronchial circulation via the azygos, hemiazygos, and intercostal veins

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33
Q

bronchial venous blood returns back to where

A

the right atrium

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34
Q

about 2/3 of the bronchial capillary blood is thought to drain into where?

A

anastomoses or communicating vessels that empty into the pulmonary veins to return to the left atrium

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35
Q

what does the bronchial capillary blood draining into the left atrium communication provide?

A

small volume of poorly oxygenated bronchial venous blood to the freshly oxygenated blood in the pulmonary vein

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36
Q

Pulmonary circulation is in series with the _____ circulation, therefore blood flow is _____

A

in series with systemic circulation, therefore blood flow is the same in both

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37
Q

how do the vessel walls in the pulmonary circuit compare to the walls in the systemic circuit

A

Vessel walls of the pulmonary vasculature are much thinner and contain less smooth muscle compared to segments in the systemic circulation

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38
Q

Structurally, the ____ _____ more closely resemble systemic veins than arteries

A

pulmonary arteries more closely resemble systemic veins

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39
Q

speaking of high flow rates, does the pulmonary or systemic circulation have lower high flow rates?

A

pulmonary vascular pressures are considerably lower

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40
Q

average PA pressure

A

13-19 mmHg

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41
Q

what causes the lower pulmonary vascular pressure?

A

the lack of high resistance arterioles

-affects blood flow distribution in the lung

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42
Q

Fick principle for cardiac output

A

the amount of O2 uptake or consumption by the body per minute is equal to the cardiac output times the difference in oxygen content b/w arterial and mixed venous blood

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43
Q

The lung is greatly designed for gas exchange, but it is ideally suited for other functions unrelated to gas exchange because….

A

the large blood volume that passes through the lung each minute

-immense capillary surface available for metabolism

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44
Q

what are the four functions of pulmonary

A
  1. gas exchange
  2. blood filter
  3. blood reservoir
  4. metabolism of circulating substances
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45
Q

what does the meshwork of capillary vessels do to act has a blood filter in the lungs?

A

trap emboli and large particles to keep from reaching the coronary or systemic vasculature

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46
Q

how are emboli trapped by pulmonary vessels later removed?

A

enzymatic processes, macrophage ingestion, or absorption into the lymphatic system

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47
Q

how do the vessels of the pulmonary system help function as a blood reservoir?

A

vessels are very compliant and easily distant

since vessels are an extension of the left atrium, they act as a blood reservoir, supplying blood to the left ventricle and maintaining output

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48
Q

pulmonary vessels contain how much blood

A

450-900 ml of blood

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49
Q

which cells in the lumen are involved in the uptake or metabolic conversion of several vasoactive substances in the circulation

A

endothelial cells

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50
Q

what are some things that the lungs release that help with metabolism of circulating substances

A
  • biologically active compounds into circulation
  • histamine
  • prostaglandins,
  • leukotrienes
  • platelet activating factor
  • heparin
  • serotonin
  • nitric oxide
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51
Q

where are mast cells found

A
  • in most tissues of body, especially those that interact with the environment
  • skin, lungs, GI tract, mouth, nose, blood brain barrier
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52
Q

when do mast cells detect and respond to?

A

-foreign substances

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53
Q

when triggered, what do mast cells release?

A
  • histamine
  • prostaglandins
  • heparin
  • tryptase
  • cytokines
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54
Q

Pulmonary artery branches rapidly give rise to nearly

A

300 billion pulmonary capillaries

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55
Q

gas exchange between the _____ and ____ occurs within the lung capillaries

A

alveolar gases and blood occurs within the lung capillaries

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56
Q

gas exchange between alveoli and pulmonary capillary blood is by

A

simple diffusion

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57
Q

O2 diffuses from the ___ to the ____

CO2 diffuses from the ____ to the ____

A

O2 diffuses from the alveolus to the pulmonary capillary blood
CO2 diffuses from the pulmonary capillary to the alveolus

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58
Q

what is the alveolar-arterial gradient?

A

a measure fo the difference between the alveolar concentration (A) of oxygen and the arterial (a) concentration of oxygen

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59
Q

when is the alveolar-arterial gradient used?

A

in diagnosing the source of hypoxemia

-helps isolate the location of the problem as either intrapulmonary (within lungs) or extra pulmonary (somewhere else in body)

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60
Q

An abnormally increase A-a gradient suggest a defect in

A
  • diffusion
  • V/Q (ventilation/perfusion ratio) mismatch
  • or right-to left shunt
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61
Q

what is hypoxemia

A

low concentration of O2 in the blood

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62
Q

what is oxygenation

A

the process where oxygen enters the bloodstream via the lungs

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63
Q

adequate oxygenation of the blood depends on many factors such as…

A
  • atmospheric pressure (Patm)
  • fraction of oxygen in inspired air (FiO2)
  • movement of oxygen into the lungs (ventilation)
  • adequate blood flow in the pulmonary capillaries (perfusion)
  • oxygenated alveoli that are perfused with blood (ventilation-perfusion matching)
  • movement of oxygen across the alveolar-capillary membrane (diffusion)
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64
Q

any problems with one or more of these factors will cause inadequate oxygenation of the blood and would be reflected as

A

low arterial oxygen partial pressure

low O2 which is hypoxemia

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65
Q

hypoxemia is caused when

A

there is not enough oxygen getting into the alveoli

-not enough oxygen transferred into the capillary blood

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66
Q

what is the alveolar-arterial oxygen gradient (A-a gradient)

A

difference (gradient) between alveolar oxygen pressure and arterial oxygen pressure

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67
Q

the 5 main mechanisms of hypoxemia fall under what 2 main categories

A
  1. not enough oxygen getting into the alveoli (will have normal A-a)
  2. not enough oxygen transferred into the capillary blood (will have elevated A-a)
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68
Q

what 2 main mechanisms of hypoxemia fall under the category of not enough oxygen getting into the alveoli

A
  1. low atmospheric pressure ex: high altitude

2. hypoventilation ex: heroin overdose

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69
Q

what 3 main mechanisms of hypoxemia fall under the category of not enough oxygen transferred into the capillary bed

A
  1. ventilation-perfusion mismatch ex: atelectasis
  2. right-to-left shunting ex: atrial septal defect
  3. diffusion defects ex: pneumonia
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70
Q

what is the equation for A-a gradient

A

A-a gradient = PAO2 - PaO2

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71
Q

what is the expected normal A-a gradient

A

< (age/4) +4

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72
Q

how to calculate the A-a gradient

A

use the alveolar gas equation and values from the arterial blood gas

step 1: calculate PAO2 (at sea level)
PAO2 = (Patm-Pwater) FiO2 - PaCO2/.8
step2: calculate A-agradient: PAO2-PaO2
step 3: compare expected A-a to calculated A-a v

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73
Q

what pH is acidic

A

under 7.35

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74
Q

what pH is basic

A

over 7.45

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75
Q

what PaCO2 is acidic

A

greater than 45

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76
Q

what PaCO2 is basic

A

less than 35

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77
Q

what bicarb is acidic

A

less than 22

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78
Q

what bicarb is basic

A

greater than 26

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79
Q

respiratory acidosis is

A

low pH, high PaCO2, normal bicarb

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80
Q

what is respiratory alkalosis

A

high pH, low PaCO2, normal bicarb

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81
Q

what is metabolic acidosis (simple)

A

low pH, normal PaCO2, and low bicarb

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82
Q

what is metabolic alkalosis (simple)

A

high pH, normal PaCO2, and high bicarb

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83
Q

Repiratory processes alter the blood pH by changing the

A

carbon dioxide levels

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84
Q

what is the main way the human body eliminates acid and maintains acid-base homeostasis

A

CO2 elimination via the lungs

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85
Q

what is respiratory acidosis (explanation)

A

when CO2 accumulates in the blood (elevated PaCO2) like when a person hypo ventilates, acid builds up and the pH decreases

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86
Q

what is respiratory alkalosis (explanation)

A

increase CO2 elimination (low PaCO2) like when a person hyperventilates, the amount of acid in the blood decreases and the pH increases

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87
Q

in the following ABG, is there. respiratory acidosis or respiratory alkalosis?

ABG: 7.32/50/98
99% O2 saturation on room air

A

alkalosis

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88
Q

what is external respiration

A

the exchange of gas (CO2 and O2) between the lungs (alveoli) and blood (pulmonary capillaries)

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89
Q

gas exchange occurs down a pressure gradient via ____ across the ____ _____

A

via diffusion

across the respiratory membrane

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90
Q

gases move from an area of

A

high concentration (high pressure) to low concentration (low pressure)

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91
Q

factors affecting rate of gas diffusion

A
  1. thickness of membrane
  2. surface area of membrane
  3. diffusion coefficient of gas in membrane
  4. partial pressure (concentration) difference of gas on either side of membrane
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92
Q

CO2 diffuses ___ more rapidly than O2

A

20x

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93
Q

laws that govern gas exchange

A

Boyles
Charles
ideal gas
henry

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94
Q

Boyles law

A

at constant temperature, pressure and volume vary inversely

P1 x V1 = P2 x V2

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95
Q

Charles law

A

movement of gases is dependent on temperature
temperature and volume vary directly

V/T = k

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96
Q

ideal gas law (dalton’s)

A

each gas in a mixture will exert its own pressure depending on the # of moles present and the temperature and volume of the mixture

PV = nRT

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97
Q

henry’s law

A

the absolute concentration of a gas dissolved in a liquid is dependent on the solubility coefficient of that gas in that liquid

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98
Q

during quiet inspiration, what happens to the volume and pressure

A

lung volume increases
pressure in lungs decrease
thoracic pressure decreases (5 mmHg below atmospheric pressure)

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99
Q

what is the basic thing to remember about Charle’s law of gases

A

gases tend to expand when heated

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100
Q

Dalton’s law of partial pressures tells us that

A

the total pressure in a mixture of gas is the sum of the partial pressures of each gas

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101
Q

the solubility of a gas in any solvent is ____ as the pressure over the solvent increase

A

the solubility of a gas in any solvent is increased as the pressure over the solvent increases

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102
Q

the solubility of the gas increases in direct promotion to what

A

its partial pressure above the solution

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103
Q

the solubility of gases in water ____ with increasing temperatures

A

decreases with increasing temperatures

104
Q

what pressure in the lung can influence the distribution of blood flow and vascular resistance?

A

vascular segments (arteries, capillaries, and veins)

extravascular pressures (intrathroacic or intrapleural)

transmural pressure

105
Q

mean hydrostatic pressure in the arteries

A

pulmonary: 13-19
systemic: 90

106
Q

mean hydrostatic pressure in capillaries

A

pulmonary: 10
systemic: 30

107
Q

mean hydrostatic pressure in veins

A

pulmonary: 5
systemic: 10

108
Q

mean hydrostatic pressure in atria

A

pulmonary: 4
systemic: 2

109
Q

intravascular hydrostatic pressure refers to

A

the actual pressure inside pulmonary vessels relative to atmospheric pressure

110
Q

the pressure drop b/w pulmonary artery and capillary is small compared to systemic vessels bc

A

the lung lacks high resistance arterioles

111
Q

the lack of arterioles in the lungs minimizes what

A

active regulation of lung blood flow distribution

112
Q

intravascular driving pressure for pulmonary circulation

A

the difference b/w inflow and outflow pressures

difference b/w pulmonary arterial (Pa) and left atrial pressure (Pla)

113
Q

the normal mean driving pressure is about

A

11 mmHg

114
Q

in the pulmonary circulation, a small driving pressure is adequate because

A

of the relatively low resistance to blood flow

115
Q

what does transmural pressure refer to

A

the pressure difference between the inside and outside of some walled structure

116
Q

because airway and blood vessels walls are distensible, pressure differences between the inside and outside can affect….

A

their diameter, therefore the resistance they offer to air or blood flow

117
Q

what is intrathoracic pressure

A

the pressure immediately outside large lung vessels

118
Q

during quiet breathing, intrathoracic pressure is less than

A

atmospheric pressure and becomes increasingly subatmospheric with inspiration

119
Q

large vessels and airways tend to passively dilate with…

A

inspiration as the outside intrathoracic pressure decreases

120
Q

these larger lung vessels, whose outside pressure is intrathoracic are referred to as

A

extra alveolar vessels

121
Q

the pressure immediately outside the lung capillaries is

A

alveolar pressure

122
Q

how does alveolar pressure affect alveolar vessels

A

the diameter and resistance to blood flow offered by these

123
Q

when alveolar pressure is increased, what does it do to the lung capillary and flow

A

narrow (squeeze) the lung capillary and increase resistance to flow

124
Q

the transmural pressure differences in alveolar vessels can also affect

A

resistance to blood flow
intravascular pressures
blood flow distribution

125
Q

what is surfactant

A

phospholipid that reduces the surface tension of water and is secreted and lines the interior surface of the alveoli

126
Q

surfactant decreases surface tension most at ____ and least at ____

A

most at low volumes and least at high volumes

127
Q

surfactant makes surface tension in the alveoli vary with

A

lung volume

128
Q

what is surface tension and what does it cause

A

cohesive force b/w liquid molecules

causes the inward collapse (recoil) of the alveoli

129
Q

LaPlace law

A

P = 2T/rP

pressure required to keep alveolus open

130
Q

small alveoli have higher ___ ____ and are harder to keep open

A

collapsing pressure

131
Q

a decrease in alveolar surface tension by surfactant causes a decrease in….

A

collapsing pressure in alveolus

132
Q

surfactant increases lung compliance which in turn decreases….

A

the work of expanding lungs during inspiration

133
Q

neonatal respiratory distress syndrome is caused by

A

a deficiency or absence of surfactant

134
Q

how does neonatal RDS affect V/Q

A

decreases V/Q

collapsed alveoli are not ventilated and do no participate in gas exchange which results in hypoxemia

135
Q

additional important lung products

A
  • prostaglandins
  • histamine
  • kallikrein
  • inactive kininogens
  • angiotensin-converting enzyme (ACE)
136
Q

what does histamine do

A

binds receptors on smooth muscle cells induce vasodilation, bronchoconstriction

137
Q

what does kallikrein do

A

catalyzes proteolytic cleavage of kininogens in kinin synthesis

138
Q

ACE inactivates

A

bradykinin

139
Q

ACE inhibitors increase…

A

bradykinin which leads to cough, angioedema

140
Q

the upright human lungs measures about ____ from the apex to the base

A

30 cm

141
Q

the pulmonary artery enters the lung at the level of the

A

hilum

about midway between the apex and base of the lung

142
Q

in order for the right heart to pump blood to the apex of the lung, what must it pump against

A

a column of blood about 15 cm high or against a pressure head of about 15 cm H2O resulting from gravity

143
Q

because the right heart has a lot to push against, the mean intravascular pressure at the lung apex is

A

11 cm H2O lower than arterial pressure at the hilum

144
Q

mean intravascular pressure at the BASE of the lung is about

A

11 cm H2O higher than pulmonary arterial pressure at the hilum

145
Q

due to gravitational forces, both intravascular pressures and blood flow are considerably ____ at the apex than at the base of the lung

A

less at the apex than at the base of the lung

146
Q

when a person assumes a supine position, the pressure differences b/w the apex and base are ____, therefore results in more uniform distribution of blood flow and smaller vascular pressure differences

A

differences b/w the apex and base are less

147
Q

alveolar pressure may be above atmospheric pressure in briefly during (2)

A
  1. forced expiration

2. chronically during positive pressure breathing

148
Q

at a given blood flow, ____ in alveolar pressure are generally reflected by nearly equivalent increases in pulmonary arterial pressure up to about 8 cm H2O

A

increases

149
Q

what is alveolar hypoxia

A

when the airway or alveolar PO2 is lower than normal

150
Q

what is hypoxic pulmonary vasoconstriction

A

constriction of the arterial vessels leading to them

-redirects blood flow away from poorly oxygenated alveoli towards alveoli that have higher PO2 levels

151
Q

HPV is a mechanism that normally operates to help optimize or improve…

A

gas exchange by decreasing blood flow to poorly oxygenated alveoli

152
Q

pulmonary shunting is

A

portion of the cardiac output that moves from the right to the left side of the heart w/o being exposed to alveolar oxygen (blood flow with no O2) perfusion with out ventilation

V/Q = 0
always pathological

153
Q

normal anatomic shunt

A

2-3% of cardiac output

thebesian veins, pleural and bronchial blood flow

154
Q

abnormal anatomic cardiac shunt

A

ASD, VSD, TOF, DORV (double outlet right ventricle)

155
Q

pulmonary shunt leads to

A

hypoxemia as alveoli collapse or fill with fluid or exudate (atelectasis, pulmonary edema, pneumonia)

156
Q

major difference b/w shunt and V/Q mismatch

A

V/Q mismatch responds to oxygen therapy

shunt is refractory and doesn’t respond easily

157
Q

true shunt are

A

autonomic shunts and capillary shunts

158
Q

intrapulmonary shunting is

A

blood flow through pulmonary capillaries w/o participating in gas exchange

159
Q

anatomic shunt exists when

A

blood passes through an anatomic channel of the heart and does not pass through the lungs

caused by: congenital heart disease, intrapulmonary fistula, vascular lung tumors

160
Q

capillary shunts are commonly caused by

A

alveolar collapse or atelectasis, alveolar fluid accumulation or alveolar consolidation

161
Q

capillary + anatomic shunt =

A

absolute or true shunt

does not respond well to O2 therapy bc alveolar oxygen does not meet the shunted blood

162
Q

relative shunt

A

pulmonary capillary perfusion is in excess of alveolar ventilation

163
Q

venous admixture

A

end result of pulmonary shunting

mixing of shunted, non-deoxygenated blood with deoxygenated blood

164
Q

ventilation perfusion ratio

A

V/Q
the relationship of the overall alveolar ventilation to the overall pulmonary blood flow

normal: 4:5 or 0.8-1

165
Q

patients with shunts are more ____ than those with VQ mismatch and they may require ___ _____

A

hypoxemia than those with VQ mismatch and they may require mechanical ventilators

166
Q

Zone 1 of the lung

A

vessels are compressed and there is no blood flow but you get oxygenation
Palv > Pa > Pv

167
Q

zone 2 of the lung

A

“vascular waterall”: the flow is independent of the eventual venous pressure and depends only on the difference b/w pulmonary arterial pressure and alveolar pressure
Pa > P alv > Pv = flow occurs but with resistance

168
Q

Zone 3 of the lung

A

the venous pressure is greater than the alveolar pressure so that flow depends on the arteriovenous pressure difference
Pa > Pv > Palv = capillary dilation = less resistance = more flow

169
Q

conditions that cause an entire lung to convert to zone 1

A
  1. blood loss (hemorrhage) hypovolemia

2. positive pressure ventilation

170
Q

the bulk of the lung in most normal healthy people and in most postures is represented by what zone

A

2

171
Q

which zone has the highest blood flow

A

zone 3

172
Q

in patients, how can pulmonary vascular resistance be obtained?

A

by using a Swan-Ganz or pulmonary artery catheter

173
Q

where is the Swan-Ganz and catheter inserted?

A

inserted into a systemic vein (ex: jugular) and advanced through the right heart into the pulmonary artery

174
Q

what does the Swan-Ganz and catheter directly measure?

A
  • used to measure pulmonary arterial (Pa) and estimate left atrial pressure (Pla) and determine blood flow (ex: CO)
  • can therefore compute PVR
175
Q

how much of the total PVR resides in the capillaries

A

50-60%

176
Q

PVR is ____ of SVR bc

A

1/10 of SVR b/c low pressure system

177
Q

important to recognize that the distribution of PVR likely varies with changes in

A

blood flow, left atrial pressure, alveolar pressure and body position

178
Q

whenever blood flow to the lung or left atrial pressure is increase, what happens to the calculated PVR

A

decreases

179
Q

PVR declines with increase in blood flow and is accounted for by

A

capillary recruitment and distension

180
Q

when blood flow or Pla is increase, previously closed capillaries are ___ and patent capillaries are further distended

A

recruited (opened)

181
Q

With more and wider parallel channels (capillaries) available for flow, what happens to the flow and resistance

A

calculated resistance to flow declines bc resistances arranged in parallel

182
Q

Lung inflation affects PVR because of the influence of

A

intrathoracic pressure and alveolar size upon extra-alveolar and alveolar vessels

183
Q

intrapleural (intrathoracic) pressure becomes more sub atmospheric during ____ which increases transmural pressure to ______

A

inspiration

which increases transmural pressure to passively dilate extra-alveolar vessels

184
Q

flow resistance in these vessels diminish as

A

lung volume increases

185
Q

As lung volume is increased from residual volume (RV) to total lung capacity (TLC), what happens to vascular resistance

A

steadily declines in extra-alveolar vessels

186
Q

as alveoli expand to larger volumes, they to do what to alveolar vessels

A

tend to compress and narrow alveolar vessels

187
Q

when is PVR typicaly lowest or at, or close to

A

FRC (function residual capacity) or normal resting end-expiration

188
Q

what is hematocrit

A

percentage of the total blood that is occupied by red cells

189
Q

an increase in the number of red cells (increased hematocrit) increases the viscosity of red cells and therefore calculated PVR is also

A

increased

190
Q

increase PVR (7)

A 
sympathetic innervation
a-Adrenergic agonist 
thromboxane/PGE2 
endothelin-1
angiotension
histamine
alveolar hypoxemia
191
Q

decrease PVR (7)

A 
parasympathetic innervation
acetylcholine
B-adrenergic agents
PGE1 
prostacyclin
nitric oxide
bradykinin
192
Q

adult lung has about how much alveoli

A

300 million alveoli each surrounded by a capillary mesh

193
Q

gas exchange is optimal in alveoli where

A

the fraction of alveolar ventilation (V) is matched to the fraction of cardiac output (Q) perfusing that alveolus

194
Q

some alveoli may be over ventilated relative to their blood flow and exhibit a V/Q of

A

over 1.0

195
Q

other alveoli may be over-pursued relative to their ventilation and have a V/Q of

A

<0.8

196
Q

at extremes, some alveoli may be ventilated but received no perfusion, so V/Q is

A

infinite V/Q

197
Q

alveoli may be perfused but not ventilated which makes the V/Q

A

very low V/Q

198
Q

V/Q match

A

local mechanisms adjust for poor air flow and/or poor blood flow

199
Q

Pulmonary arterioles have receptors that sense

A

H+ concentrations and low O2 (chemoreceptors)

200
Q

Fick’s law of diffusion: diffusion is proportional to

A

partial pressure difference (gradient) and surface area

201
Q

Fick’s law of diffusion is inversely proportional to

A

membrane thickness and diffusion distance

202
Q

hemoglobin contains

A

4 heme molecules and 1 globing molecule

203
Q

each heme molecule can carry

A

4 O2 molecules

204
Q

1mg hemoglobin can carry

A

1.34 ml of O2

205
Q

internal respiration occurs as

A

simple diffusion

206
Q

carbon dioxide diffuses out of the __ and goes where

A

diffuses out of the tissue, cross the interstitial fluid and enter the blood

-then carried back to the lungs either bound to hemoglobin, dissolved in plasma, or in a converted form

207
Q

oxygen delivery is a function of

A

arterial oxygen content and cardiac output

208
Q

oxygen consumption

A

is the rate at which tissues take up oxygen and is a function of oxygen delivery and amount of oxygen that is extracted by tissues

209
Q

Hgb is 50% saturated at a plasma PO2 of approx

A

27 mmHg

210
Q

Normal venous blood has PvO2 at ___ and oxyhemoglobin sat at ___

A

40 mmHg

sat of 75%

211
Q

normal arterial blood has PaO2 of ___ and oxyhemoglobin sat of

A

97 mmHg

sat of 97%

212
Q

Haldane effect

A

PO2 affects the ability of the blood to carry CO2

213
Q

Bohr effect

A

a decrease in pH shifts the curve to the right

incr pCO2, incr temp, incr DPG

214
Q

an increased P50 causes a

A

decreased affinity of Hb to O2

215
Q

lower P50 indicates a

A

leftward shift and a higher affinity of Hb to O2

216
Q

fetal hemoglobin has a

A

higher affinity for oxygen

causes a leftward shift and lower P50

217
Q

methemoglobinaemia

A

Fe3+

leftward shift = lower P50

218
Q

carbon monoxides binds to hemoglobin ___ times more readily than with oxygen

A

240 times

shifts curve to the left

219
Q

with an increased level of carbon monoxide, a person can suffer from

A

severe hypoxemia while maintaining a normal PO2

220
Q

anemia in terms of blood O2/PO2 curve

A

increase in 2,3-DPG shifts curve to the right

-decreased affinity for O2 translates to better O2 offloading to tissues

221
Q

acute high altitude

A

thin air, causes hyperventilation

decreases PCO2 and increase pH shifts curve to the left

222
Q

acclimation to high altitude

A

polycythemia occurs

increases 2,3 DPG and shifts curve to the right

223
Q

factors that increase C(a-v)O2 and decrease SvO2

A
  • decreased CO
  • exercise
  • hyperthermia
  • seizures
  • shivering in post-op patient
224
Q

factors that decrease the C(a-v)O2 and increase SvO2

A
  • increased CO
  • skeletal muscle relaxation
  • peripheral shunting
  • certain poisons
  • hypothermia
225
Q

when the C(a-v)O2 increases….

A

the SvO2 decreases

226
Q

three main forms of CO2 transport in blood

A
  1. as bicarbonate ions (70%)
  2. as carbamino-hemoglobin (15-25%)
  3. dissolved in plasma (5%)
227
Q

where are three influences on control of respiration

A
  1. chemical influences of the respiratory center of the brain neural influences
  2. cortical influences voluntary controls in the medullary rhythmicity center and pontine respiratory center neurons limit inspiratory
  3. proprioceptive stretch receptors in the lungs
228
Q

how does the medullary rhythmicity center control respiration

A

autorythmic inspiratory and expiratory neurons sets the basal ventilation

229
Q

how does the pontine respiratory center neurons limit inspiratory

A

impulses causing shorter cycles which increases ventilation rate

230
Q

the respiratory center of the brain is controlled by a

A

negative feedback pathway

231
Q

Increased pO2, decreased pCO2, and a drop in H+ all interact to

A

discourage ventilation to retain more CO2

232
Q

decreased pO2, increased pCO2, and a rise in H+ all interact to

A

encourage ventilation to blow off more CO2

233
Q

central chemoreceptors control ___% of the responses

A

70%

medulla

234
Q

peripheral chemoreceptors control ___% of responses

A

30%

carotid and aortic bodies

235
Q

Pulmonary arteries have thin walls and are under lower pressure. what does this create?

A

lower hydrostatic pressure gradients

this minimizes the tendency for fluid to filter out of the pulmonary capillaries into the airspaces

236
Q

hydrostatic pressure

A

tends to push fluid out of vessels

237
Q

colloid oncotic pressure tends to

A

pull fluid into vessels

238
Q

what are the causes of pulmonary edema

A
  1. high pressure

2. low pressure

239
Q

high pressure edema

A
  • hydrostatic, cardiogenic
  • common w left heart failure results in more fluid filtration from the vascular space than can be returned by plasma oncotic forces

-left atrial pressure threshold for pulmonary edema is about 25 mmHg

240
Q

low pressure edema

A
  • high permeability, noncardiogenic

- results from an increase in permeability of the barrier that separates blood from the tissues

241
Q

what is neurogenic pulmonary edema

A

from head injury, SAH, intercebral hemorrhage

242
Q

cariogenic pulmonary edema comes from

A

heart failure and fluid overload (kidney and liver)

243
Q

noncardiogenic pulmonary edema comes from

A

lung and capillary

244
Q

5 causes from pulmonary edema in relation to starling forces

A
  1. increased hydrostatic pressure
  2. reduced oncotic pressure
  3. reduced lymphatic drainage
  4. increased surface tension
  5. increased capillary permeability
245
Q

starling forces favor movement of fluid from

A

inside capillaries to the interstitial space

246
Q

what is obstructive lung disease

A
  • have SOB due to difficulty exhaling all the air from the lungs.
  • exhaled air comes out more slowly than normal
247
Q

what are types of obstructive lung disease

A
  1. COPD
  2. asthma
  3. bronchiectasis
  4. cystic fibrosis
248
Q

what is restrictive lung disease

A

cannot fully fill their lungs with air

249
Q

types of restrictive Lung disease

A
  1. interstitial lung disease
  2. sarcoidosis
  3. obesity
  4. scoliosis
    neuromuscular disease
250
Q

in an oxygenator, gas transfer from the

A

gas to the liquid phase

251
Q

what is gas transfer driven by in an oxygenator

A

diffusion according to the partial pressure difference of the particular gas

252
Q

the region in which variation in velocity occurs is defined as

A

boundary layer

253
Q

blood or any other viscous fluid flowing past either a stationary surface or a bubble will have variations in velocity from

A

zero at the interface surface to that of the free stream

254
Q

the major resistance to gas diffusion occurs in the

A

blood phase

255
Q

efforts to improve gas exchange

A
  1. increase welling times
  2. increasing driving gradient
  3. decreasing the diffusion path by making the surface of the membrane irregular or positioning the elements within the flow stream to disrupt the smooth flow
256
Q

an eddy current has an impact on the

A

boundary layer of the fiber, disrupting its development and reducing its thickness

ventilation, oxygenation, respiration (1 decks)

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