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
2
Q
How do you calculate the minute ventilation?.
A
Tidal volume x breathing rate
3
Q
What is the average tidal volume?
A
0.5 L
4
Q
What is the alveolar ventilation?
A
The volume of gas leaving and entering the alveoli
5
Q
How do you calculate the alveolar ventilation rate?
A
(Tidal volume - dead space) x breaths per minute
6
Q
What is the dead space?
A
It is the region of the respiratory system which does not participate in gas exchange
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
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
9
Q
How do you calculate physiological dead space?
A
anatomical + alveolar dead space
10
Q
What is the tidal volume?
A
The volume of gas breathed in / out in a normal breath
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
12
Q
Tidal volume + inspiratory reserve volume =
A
inspiratory capacity
13
Q
What is the expiratory reserve capacity?
A
The maximum volume of air which can be expired after the tidal volume expiration
14
Q
Residual volume + expiratory reserve volume =
A
functional residual capacity
15
Q
Inspiratory capacity + functional residual capacity =
A
Total lung capacity
16
Q
What is the residual volume?
A
The volume of air which remains in the lungs even after a complete exhalation is completed
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
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
19
Q
What is hyperventilation.
A
Excessive ventilation of the lungs atop of metabolic demands which results in reduced concentrations of carbon dioxide = alkalosis
20
Q
What is the alveolar dead space?
A
The capacity of the airways which should be able to undertake gas exchange but cannot
21
Q
What is anatomical dead space?
A
The capacity of the airways that is incapable of undertaking gas exchange
22
Q
What is Bradypnoea?
A
Abnormally slow breathing
23
Q
What is tachypneoa
A
Abnormal,y fast breathing
24
Q
What factors affect lung volumes and capacities?
A
Body size, sex, disease, age and fitness (genetics)
25
How many generations are there in the respiratory zone?
7
26
How many generations are there in the lungs?
23
27
What can increase someone’s dead space?
Snorkeling
| Anaesthetic circuit
28
What can decrease someone’s dead space?
Tracheostomy
| Cricothyroidotomy
29
What direction does the chest wall have a tendency to spring in?
Outwards
30
What direction do the lungs have a tendency to recoil in?
Inwads
31
When are the forces of the chest wall and lungs in equilibrium?
At the end-tidal expiration which is the neutral position of the intact chest
32
What happens to the lung chest forces at functional residual capacity?
They are at equilibrium
33
Inspiratory muscle effort + chest recoil > lung recoil =
INSPIRATION
34
Expiratory muscle effort + chest recoil < lung recoil =
EXPIRATION
35
What are the lungs surrounded by?
A visceral pleural membrane
36
What is the inner surface of the chest covered with?
A parietal pleural membrane
37
What is the pleural cavity?
The gap between the two pleural membranes and contains protein rich pleural fluid
38
What does the intrapleural space do?
Makes the lung and chest wall work in partnership
39
What are the consequences of an intraplueral bleed?
Squashes the lung and makes it harder for the lung to expand and therefore ventilation is hindered
40
What are the consequences of a perforated chest wall?
A loss of the negative pressure in the intrapleural space, resting in a pneumothorax which reduces the effectiveness of ventilation
41
What is a haemothorax?
An accumulation of blood within the pleural cavity
42
What is a pneumothorax?
The presence of air or gas in the pleural cavity which causes collapse of the lungs
43
What type of breathing do we do on a day to day basis?
Negative pressure breathing
44
What is negative pressure breathing?
When the pressure inside the lungs is less than the pressure outside in the atmosphere, so the air is drawn in
45
What is positive pressure breathing?
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
46
What are some examples of positive pressure breathing?
CPR
mechanical ventilation - pushing air into lungs
Fighter pilots
47
What are the two classifications of inspiratory muscle forces?
A pulling force in one direction (like a syringe)
An upwards and outwards swinging force (like a bucket handle)
48
What type of inspiratory muscle force does the diaphragm use?
A unidirectional pulling force
49
What force do the ribs use for inspiration?
An upwards and outwards swinging force
50
What does maximum ventilation involve?
Full inspiratory muscle recruitment (syringe and bucket handle movement)
51
How does the pleural cavity act as a partial vacuum?
It acts as a suction to stop the lungs from collapsing
52
What does Dalton’s law describe?
The pressure of a gas mixture is equal to the sum of the partial pressures of gases in that mixture
53
What does Fick’s law state?
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
Increasing what factors of flicks was will increase the rate of diffusion?
Concentration gradient, surface area, diffusion capacity
55
What does Henry’s law describe?
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
What does Boyles law state?
At the constant temperature, the volume of a gas is inversely proportional to the pressure of the gas
57
What does Charles law state?
At a constant pressure, the volume of gas is proportional to the temperature of the gas
58
What percentage of the air is oxygen?
20.95%
59
What percentage of the air is nitrogen?
78.09%
60
What is the air like at high altitudes?
The proportions of the gases in the air is the same, however there is less air, so the volume is less
61
What happens to the proportion of oxygen in the air when a patient is under oxygen therapy?
Tethered is a lot more oxygen
62
What four things happen as air passes down the respiratory tree?
Warmed, humidified, slowed and mixed
63
What do haemaglobin monomers consist of?
a ferrous iron ion at the center of a porphyrin ring, connected to a protein chain, covalently bonded at the proximal histamine residue
64
What is meant by cooperative binding?
When an oxygen atom binds to one of haemaglobins 4 binding sites, the affinity to oxygen of the three remaining sites increases
65
Between a bound and unbound haemaglobin, which has a higher affinity for oxygen?
Bound
66
in oxygen rich areas, what is promoted?
Oxygen loading
67
In what circumstance is oxygen unloading promoted?
In oxygen starved areas as haemaglobin has a lower affinity for O2
68
What shape is the oxygen dissociation curve?
Sigmoidal
69
What causes a righwards shift in the oxygen dissociation curve?
Higher temperature
Acidosis - increased H+ ions
Hypercapnia - increased CO2 concentration
Increased 2,3-DPG
70
What change in oxygen affinity is a rightwards shift associated with?
Decreased affinity for haemaglobin binding oxygen
71
What causes a leftwards shift of the oxygen dissociation curve?
Lower temperatures
Alkalosis - lower H+ so Higher pH
Hypocapnia - Decreased CO2 in blood
Decreased 2,3-DPG
72
What happens to the oxygen carry capacity when there is a downwards shift in the oxygen dissociation curve?
Decreased oxygen carry capacity
73
What happens to the oxygen carry capacity when there is a upwards shift in the oxygen dissociation curve?
Increased oxygen carrying capacity
74
What conditions results in a decreased oxygen carrying capacity?
Anaemia
75
What condition results in an increased oxygen carry capacity for haemoglobin?
Polycythaemia
76
What is the oxygen affinity of foetal haemoglobin relative to adult haemoglobin?
Higher affinity
77
Why does HbF have a higher affinity for oxygen than HbA?
So it can extract oxygen from the mothers blood in placenta
78
At what point is foetal haemoglobin completely replaced by adult haemoglobin?
6 months after birth
79
What is a treatment of sickle cell disease involving foetal Hb?
HbF production can be pharmacologically induced in adults to treat SCD
80
Describe the allosteric behaviour of Haemoglobin?
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
What does allosteric mean?
Changes shape when something binds
82
What affect does CO have on the oxygen dissociation curve?
Downwards and leftwards shift
83
What does the downwards and leftwards shift of the oxygen dissociation curve shown by CO represent?
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
What is the oxygen affinity of myoglobin relative to Hb?
Much greater affinity than adult HbA to 'extract' oxygen from circulating blood and store it
85
Where is myoglobin found?
In skeletal muscle tissue
86
Why is myoglobin not capable of cooperative binding?
It is made of a single polypeptide with only one heme group
87
What shape is the oxygen dissociation curve for myoglobin?
Logarithmic
88
How is the onset of anareobic respiration slowed by myoglobin?
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
What features of the alveoli allow for efficient gas exchange?
High surface area to volume ratio
Covered in high density capillaries that provide many sites for gas exchange
90
What are the walls of the alveoli like?
They are thin and covered in a fluid, extracellular matrix which provides a surface for gas exchange
91
Which two processes driven by partial pressure gradients occur at the same time?
The loading of oxygen into the blood stream and the offloading of carbon dioxide out of the blood stream
92
What is external respiration a result of?
Partial pressure gradients, alveolar surface area and ventilation and perfusion matching
93
What is the partial pressure of oxygen in the oxygenated blood of the capillary after oxygen loading?
100mmHg
94
What is the partial pressure gradient of oxygen?
60mmHG
95
what is the partial pressure gradient for carbon dioxide?
5mmHg
96
How does diffusion of CO2 occur as fast as O2 despite the lower partial pressure gradient?
CO2 has a greater solubility in the blood compared to oxygen
97
How fast is the equilibrium between the alveolar air and capillaries reached for oxygen?
The first 1/3 of the length of the capillary is reached within 1/3 of a second
98
How fast is the equilibrium between the alveolar air and capillaries reached for carbon dioxide?
1/2 the length of the capillary is reached within 1/2 a second
99
what does a severe ventilation-perfusion mismatch indicate?
Severe lung disease
100
What is the definition of perfusion?
The passage of blood, a blood substitute or other fluid through the blood vessels or other natural channels in an organ or tissue
101
What are the three methods that CO2 molecules are transported in the blood from tissues to the lungs?
1. Dissolving directly into the blood
2. Binding to haemoglobin
3. Carried as a bicarbonate ion
102
What properties of carbon dioxide make it good at being transported?
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
What is formed when carbon dioxide binds to haemoglobin?
Carbaminohaemoglobin
104
How are the majority of carbon dioxide molecules carried around the blood?
By the bicarbonate buffer system
105
What enzyme is used within the red blood cells to convert the carbon dioxide into carbonic acid (H2CO3)
Carbonic anhydrase
106
what does carbonic acid dissociate into?
Bicarbonate ions and hydrogen ions
107
What allows for the continued uptake of carbon dioxide into the blood?
The fact that carbon dioxide is very quickly converted into bicarbonate ions
108
How is the change in pH which could arise from excess H+ ions avoided?
Haemoglobin binds to the free H+ ions
109
What is chloride ion shift?
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
When is the bicarbonate ion shuttle back into the RBC in exchange for the chloride ion during the chloride shift?
when the blood reaches the lungs
111
How is the carbonic acid intermediate reformed?
The bicarbonate ion binds to the H+ ion which has dissociated from the haemoglobin
112
How does carbon dioxide bind to haemoglobin?
It binds to the amine group of the haemoglobin molecule
113
What is the benefit of the bicarbonate buffer system?
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
What is the pulmonary transit time?
0.75 seconds
115
What part of the 0.75 seconds of pulmonary transit time does diffusion occur in?
the first 0.25 seconds
116
What happens in the last 0.5 seconds of the pulmonary transit time?
It is the reserve time - this is so that when diffusion is impaired, the reserve time is needed for diffusion to be complete
117
What happens to the transit time and reserve time when we exercise?
Transit time decreases and reserve time also gets shortened
118
What does the conducting zone consist of?
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
How does cricothyroidotomy decrease dead space?
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
Describe how a fighter jet pilot wearing an oxygen mask is an example of positive pressure breathing?
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
What is hypercapnia?
High CO2.
