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Cvr > Ventilation And Gas Exchange > Flashcards

Ventilation And Gas Exchange Flashcards

1
Q

What is the minute ventilation?

A

The volume of gas entering and leaving the lungs over a minute

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2
Q

How do you calculate the minute ventilation?.

A

Tidal volume x breathing rate

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3
Q

What is the average tidal volume?

A

0.5 L

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4
Q

What is the alveolar ventilation?

A

The volume of gas leaving and entering the alveoli

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5
Q

How do you calculate the alveolar ventilation rate?

A

(Tidal volume - dead space) x breaths per minute

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6
Q

What is the dead space?

A

It is the region of the respiratory system which does not participate in gas exchange

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7
Q

What is the conducting zone?

A

The first 16 generations of bronchi, equivalent to the anatomical dead space as no gas exchange occurs here

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8
Q

What are non-perfused parenchyma?

A

Alveoli without a blood supply and therefore do not participate in gas exchange, equivalent to the alveolar dead space

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9
Q

How do you calculate physiological dead space?

A

anatomical + alveolar dead space

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10
Q

What is the tidal volume?

A

The volume of gas breathed in / out in a normal breath

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11
Q

What is the inspiratory reserve volume?

A

The maximum volume of gas which can be breathed in on top of the tidal volume

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12
Q

Tidal volume + inspiratory reserve volume =

A

inspiratory capacity

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13
Q

What is the expiratory reserve capacity?

A

The maximum volume of air which can be expired after the tidal volume expiration

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14
Q

Residual volume + expiratory reserve volume =

A

functional residual capacity

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15
Q

Inspiratory capacity + functional residual capacity =

A

Total lung capacity

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16
Q

What is the residual volume?

A

The volume of air which remains in the lungs even after a complete exhalation is completed

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17
Q

What is the vital capacity?

A

Inspiratory reserve volume + expiratory reserve volume + tidal volume

It is the total volume of air which can be expelled from the lungs at maximum expiratory effort

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18
Q

What is the definition of the vital capacity of the lungs.

A

The greatest volume of air which can be expelled from the lungs after taking the deepest possible breath

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19
Q

What is hyperventilation.

A

Excessive ventilation of the lungs atop of metabolic demands which results in reduced concentrations of carbon dioxide = alkalosis

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20
Q

What is the alveolar dead space?

A

The capacity of the airways which should be able to undertake gas exchange but cannot

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21
Q

What is anatomical dead space?

A

The capacity of the airways that is incapable of undertaking gas exchange

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22
Q

What is Bradypnoea?

A

Abnormally slow breathing

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23
Q

What is tachypneoa

A

Abnormal,y fast breathing

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24
Q

What factors affect lung volumes and capacities?

A

Body size, sex, disease, age and fitness (genetics)

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25
Q

How many generations are there in the respiratory zone?

A

7

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26
Q

How many generations are there in the lungs?

A

23

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27
Q

What can increase someone’s dead space?

A

Snorkeling

Anaesthetic circuit

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28
Q

What can decrease someone’s dead space?

A

Tracheostomy

Cricothyroidotomy

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29
Q

What direction does the chest wall have a tendency to spring in?

A

Outwards

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30
Q

What direction do the lungs have a tendency to recoil in?

A

Inwads

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31
Q

When are the forces of the chest wall and lungs in equilibrium?

A

At the end-tidal expiration which is the neutral position of the intact chest

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32
Q

What happens to the lung chest forces at functional residual capacity?

A

They are at equilibrium

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33
Q

Inspiratory muscle effort + chest recoil > lung recoil =

A

INSPIRATION

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34
Q

Expiratory muscle effort + chest recoil < lung recoil =

A

EXPIRATION

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35
Q

What are the lungs surrounded by?

A

A visceral pleural membrane

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36
Q

What is the inner surface of the chest covered with?

A

A parietal pleural membrane

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37
Q

What is the pleural cavity?

A

The gap between the two pleural membranes and contains protein rich pleural fluid

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38
Q

What does the intrapleural space do?

A

Makes the lung and chest wall work in partnership

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39
Q

What are the consequences of an intraplueral bleed?

A

Squashes the lung and makes it harder for the lung to expand and therefore ventilation is hindered

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40
Q

What are the consequences of a perforated chest wall?

A

A loss of the negative pressure in the intrapleural space, resting in a pneumothorax which reduces the effectiveness of ventilation

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41
Q

What is a haemothorax?

A

An accumulation of blood within the pleural cavity

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42
Q

What is a pneumothorax?

A

The presence of air or gas in the pleural cavity which causes collapse of the lungs

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43
Q

What type of breathing do we do on a day to day basis?

A

Negative pressure breathing

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44
Q

What is negative pressure breathing?

A

When the pressure inside the lungs is less than the pressure outside in the atmosphere, so the air is drawn in

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45
Q

What is positive pressure breathing?

A

When you increase pressure in the airways, above alveolar pressure - this can be achieved through performing CPR, or using a mask when in a fighter plane

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46
Q

What are some examples of positive pressure breathing?

A

CPR
mechanical ventilation - pushing air into lungs
Fighter pilots

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47
Q

What are the two classifications of inspiratory muscle forces?

A

A pulling force in one direction (like a syringe)

An upwards and outwards swinging force (like a bucket handle)

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48
Q

What type of inspiratory muscle force does the diaphragm use?

A

A unidirectional pulling force

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49
Q

What force do the ribs use for inspiration?

A

An upwards and outwards swinging force

50
Q

What does maximum ventilation involve?

A

Full inspiratory muscle recruitment (syringe and bucket handle movement)

51
Q

How does the pleural cavity act as a partial vacuum?

A

It acts as a suction to stop the lungs from collapsing

52
Q

What does Dalton’s law describe?

A

The pressure of a gas mixture is equal to the sum of the partial pressures of gases in that mixture

53
Q

What does Fick’s law state?

A

Molecules will diffuse from regions of high concentration to low concentration at a rate proportional to the concentration gradient, the exchange scarce area and the diffusion capacity of the gas, and inversely proportional to the thickness of th exchange surface

54
Q

Increasing what factors of flicks was will increase the rate of diffusion?

A

Concentration gradient, surface area, diffusion capacity

55
Q

What does Henry’s law describe?

A

At a constant temperature, the amount of gas that dissolves in a given type and volume of liquid is directly proportional to the partial pressure of that gas in equilibrium with that liquid

56
Q

What does Boyles law state?

A

At the constant temperature, the volume of a gas is inversely proportional to the pressure of the gas

57
Q

What does Charles law state?

A

At a constant pressure, the volume of gas is proportional to the temperature of the gas

58
Q

What percentage of the air is oxygen?

A

20.95%

59
Q

What percentage of the air is nitrogen?

A

78.09%

60
Q

What is the air like at high altitudes?

A

The proportions of the gases in the air is the same, however there is less air, so the volume is less

61
Q

What happens to the proportion of oxygen in the air when a patient is under oxygen therapy?

A

Tethered is a lot more oxygen

62
Q

What four things happen as air passes down the respiratory tree?

A

Warmed, humidified, slowed and mixed

63
Q

What do haemaglobin monomers consist of?

A

a ferrous iron ion at the center of a porphyrin ring, connected to a protein chain, covalently bonded at the proximal histamine residue

64
Q

What is meant by cooperative binding?

A

When an oxygen atom binds to one of haemaglobins 4 binding sites, the affinity to oxygen of the three remaining sites increases

65
Q

Between a bound and unbound haemaglobin, which has a higher affinity for oxygen?

A

Bound

66
Q

in oxygen rich areas, what is promoted?

A

Oxygen loading

67
Q

In what circumstance is oxygen unloading promoted?

A

In oxygen starved areas as haemaglobin has a lower affinity for O2

68
Q

What shape is the oxygen dissociation curve?

A

Sigmoidal

69
Q

What causes a righwards shift in the oxygen dissociation curve?

A

Higher temperature
Acidosis - increased H+ ions
Hypercapnia - increased CO2 concentration
Increased 2,3-DPG

70
Q

What change in oxygen affinity is a rightwards shift associated with?

A

Decreased affinity for haemaglobin binding oxygen

71
Q

What causes a leftwards shift of the oxygen dissociation curve?

A

Lower temperatures
Alkalosis - lower H+ so Higher pH
Hypocapnia - Decreased CO2 in blood
Decreased 2,3-DPG

72
Q

What happens to the oxygen carry capacity when there is a downwards shift in the oxygen dissociation curve?

A

Decreased oxygen carry capacity

73
Q

What happens to the oxygen carry capacity when there is a upwards shift in the oxygen dissociation curve?

A

Increased oxygen carrying capacity

74
Q

What conditions results in a decreased oxygen carrying capacity?

A

Anaemia

75
Q

What condition results in an increased oxygen carry capacity for haemoglobin?

A

Polycythaemia

76
Q

What is the oxygen affinity of foetal haemoglobin relative to adult haemoglobin?

A

Higher affinity

77
Q

Why does HbF have a higher affinity for oxygen than HbA?

A

So it can extract oxygen from the mothers blood in placenta

78
Q

At what point is foetal haemoglobin completely replaced by adult haemoglobin?

A

6 months after birth

79
Q

What is a treatment of sickle cell disease involving foetal Hb?

A

HbF production can be pharmacologically induced in adults to treat SCD

80
Q

Describe the allosteric behaviour of Haemoglobin?

A

When oxygen binds, the affinity for oxygen increases - this causes a binding site for 2,3-DPG to open up which can help the unloading of oxygen

81
Q

What does allosteric mean?

A

Changes shape when something binds

82
Q

What affect does CO have on the oxygen dissociation curve?

A

Downwards and leftwards shift

83
Q

What does the downwards and leftwards shift of the oxygen dissociation curve shown by CO represent?

A

Decreased capacity but increased affinity - eg only has 50% oxygen binding sites available, but the oxygen that does bind binds with alot more affinity, so is not released easily

84
Q

What is the oxygen affinity of myoglobin relative to Hb?

A

Much greater affinity than adult HbA to ‘extract’ oxygen from circulating blood and store it

85
Q

Where is myoglobin found?

A

In skeletal muscle tissue

86
Q

Why is myoglobin not capable of cooperative binding?

A

It is made of a single polypeptide with only one heme group

87
Q

What shape is the oxygen dissociation curve for myoglobin?

A

Logarithmic

88
Q

How is the onset of anareobic respiration slowed by myoglobin?

A

Myoglobin hods onto oxygen supply until levels in muscle are very low - this delayed release helps to slow the onset of anaerobic respiration and lactic acid

89
Q

What features of the alveoli allow for efficient gas exchange?

A

High surface area to volume ratio

Covered in high density capillaries that provide many sites for gas exchange

90
Q

What are the walls of the alveoli like?

A

They are thin and covered in a fluid, extracellular matrix which provides a surface for gas exchange

91
Q

Which two processes driven by partial pressure gradients occur at the same time?

A

The loading of oxygen into the blood stream and the offloading of carbon dioxide out of the blood stream

92
Q

What is external respiration a result of?

A

Partial pressure gradients, alveolar surface area and ventilation and perfusion matching

93
Q

What is the partial pressure of oxygen in the oxygenated blood of the capillary after oxygen loading?

A

100mmHg

94
Q

What is the partial pressure gradient of oxygen?

A

60mmHG

95
Q

what is the partial pressure gradient for carbon dioxide?

A

5mmHg

96
Q

How does diffusion of CO2 occur as fast as O2 despite the lower partial pressure gradient?

A

CO2 has a greater solubility in the blood compared to oxygen

97
Q

How fast is the equilibrium between the alveolar air and capillaries reached for oxygen?

A

The first 1/3 of the length of the capillary is reached within 1/3 of a second

98
Q

How fast is the equilibrium between the alveolar air and capillaries reached for carbon dioxide?

A

1/2 the length of the capillary is reached within 1/2 a second

99
Q

what does a severe ventilation-perfusion mismatch indicate?

A

Severe lung disease

100
Q

What is the definition of perfusion?

A

The passage of blood, a blood substitute or other fluid through the blood vessels or other natural channels in an organ or tissue

101
Q

What are the three methods that CO2 molecules are transported in the blood from tissues to the lungs?

A
  1. Dissolving directly into the blood
  2. Binding to haemoglobin
  3. Carried as a bicarbonate ion
102
Q

What properties of carbon dioxide make it good at being transported?

A

it is more soluble in the blood than oxygen

It binds to plasma proteins or can enter red blood cells and bind to haemoglobin quite easily

103
Q

What is formed when carbon dioxide binds to haemoglobin?

A

Carbaminohaemoglobin

104
Q

How are the majority of carbon dioxide molecules carried around the blood?

A

By the bicarbonate buffer system

105
Q

What enzyme is used within the red blood cells to convert the carbon dioxide into carbonic acid (H2CO3)

A

Carbonic anhydrase

106
Q

what does carbonic acid dissociate into?

A

Bicarbonate ions and hydrogen ions

107
Q

What allows for the continued uptake of carbon dioxide into the blood?

A

The fact that carbon dioxide is very quickly converted into bicarbonate ions

108
Q

How is the change in pH which could arise from excess H+ ions avoided?

A

Haemoglobin binds to the free H+ ions

109
Q

What is chloride ion shift?

A

This is where chloride ions enter into the RBC to maintain resting membrane potential, and the bicarbonate ion is transported out the red blood cell into the liquid part of the blood in exchange for this carbonate ion

110
Q

When is the bicarbonate ion shuttle back into the RBC in exchange for the chloride ion during the chloride shift?

A

when the blood reaches the lungs

111
Q

How is the carbonic acid intermediate reformed?

A

The bicarbonate ion binds to the H+ ion which has dissociated from the haemoglobin

112
Q

How does carbon dioxide bind to haemoglobin?

A

It binds to the amine group of the haemoglobin molecule

113
Q

What is the benefit of the bicarbonate buffer system?

A

The carbon dioxide is soaked up into the blood with no change to the pH of the system

Also allows people to travel and live at higher altitudes - when the partial pressure of O2 and CO2 change, the bicarbonate buffer system adjusts to regulate CO2 while maintaining the correct body pH

114
Q

What is the pulmonary transit time?

A

0.75 seconds

115
Q

What part of the 0.75 seconds of pulmonary transit time does diffusion occur in?

A

the first 0.25 seconds

116
Q

What happens in the last 0.5 seconds of the pulmonary transit time?

A

It is the reserve time - this is so that when diffusion is impaired, the reserve time is needed for diffusion to be complete

117
Q

What happens to the transit time and reserve time when we exercise?

A

Transit time decreases and reserve time also gets shortened

118
Q

What does the conducting zone consist of?

A

all the structures that provide passageways for air to travel into and out of the lungs; nasal cavity, pharynx, trachea, bronchi and some bronchioles

119
Q

How does cricothyroidotomy decrease dead space?

A

The conducting zone is known as the anatomical dead space - by performing a cricothyroidotomy, you are decreasing the anatomical dead space by bypassing half of the conducting zone

120
Q

Describe how a fighter jet pilot wearing an oxygen mask is an example of positive pressure breathing?

A

The mask pushes positive oxygen-enriched air into mouthpiece at higher-than-ambient pressure which means the pilot will find it easier to breathe in, especially during extreme manouevers in the jet.

121
Q

What is hypercapnia?

A

High CO2.

Cvr (13 decks)

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