Ventilation And Gas Exchange Flashcards
(125 cards)
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 alveolar dead space?
A
It is the region of the respiratory system which does not participate in gas exchange
7
Q
Give an example of alveolar dead space
A
Hypoperfused alveoli– alveoli with little or no blood flowing through their adjacent pulmonary capillaries
8
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
9
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
10
Q
How do you calculate physiological dead space?
A
Anatomical + alveolar dead space
11
Q
What is the tidal volume?
A
The volume of gas breathed in / out in a normal breath
12
Q
What is the inspiratory reserve volume?
A
The maximum volume of gas which can be breathed in on top of the tidal volume
13
Q
Tidal volume + inspiratory reserve volume =
A
Inspiratory capacity
14
Q
What is the expiratory reserve capacity?
A
The maximum volume of air which can be expired after the tidal volume expiration
15
Q
Residual volume + expiratory reserve volume =
A
functional residual capacity
16
Q
Inspiratory capacity + functional residual capacity =
A
Total lung capacity
17
Q
What is the residual volume?
A
The volume of air which remains in the lungs even after a complete exhalation is completed
18
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
19
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
20
Q
What is hyperventilation and what does it cause?
A
Excessive ventilation of the lungs on top of metabolic demands which results in reduced concentrations of carbon dioxide and thus alkalosis
21
Q
What is the alveolar dead space?
A
The capacity of the airways which should be able to undertake gas exchange but cannot
22
Q
What is anatomical dead space?
A
The capacity of the airways that is incapable of undertaking gas exchange
23
Q
What is bradypnoea?
A
Abnormally slow breathing
24
Q
What is tachypneoa?
A
Abnormally fast breathing
25
What factors affect lung volumes and capacities?
Body size, sex, disease, age and fitness (genetics)
26
How many generations are there in the respiratory zone?
7
27
How many generations are there in the lungs?
23
28
What can increase someone’s dead space?
Snorkeling
Anaesthetic circuit
| Anaesthetic circuit
29
What can decrease someone’s dead space?
Tracheostomy
Cricothyroidotomy
30
What direction does the chest wall have a tendency to spring in?
Outwards
31
What direction do the lungs have a tendency to recoil in?
Inwards
32
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
33
What happens to the lung chest forces at functional residual capacity?
They are at equilibrium
34
What happens when inspiratory muscle effort and chest recoil > lung recoil?
INSPIRATION
35
What happens when expiratory muscle effort and chest recoil < lung recoil?
EXPIRATION
36
What are the lungs surrounded by?
A visceral pleural membrane
37
What is the inner surface of the chest covered with?
A parietal pleural membrane
38
What is the pleural cavity?
The gap between the two pleural membranes which contains protein rich pleural fluid
39
What does the intrapleural space do?
Makes the lung and chest wall work in partnership
40
What are the consequences of an intrapleural bleed?
Squashes the lung and makes it harder for the lung to expand and therefore ventilation is hindered
41
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
42
What is a haemothorax?
An accumulation of blood within the pleural cavity
43
What is a pneumothorax?
The presence of air or gas in the pleural cavity which causes collapse of the lungs
44
What type of breathing do we do on a day to day basis?
Negative pressure breathing
45
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
46
What is positive pressure breathing and when does it happen?
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
47
What are some examples of positive pressure breathing?
CPR
Mechanical ventilation - pushing air into lungs
Fighter pilots
48
What are the two classifications of inspiratory muscle forces?
A unidirectional pulling force (like a syringe)
An upwards and outwards swinging force (like a bucket handle)
49
What type of inspiratory muscle force does the diaphragm use?
A unidirectional pulling force
50
What force do the ribs use for inspiration?
An upwards and outwards swinging force
51
What does maximum ventilation involve?
Full inspiratory muscle recruitment
52
How does the pleural cavity act as a partial vacuum?
It acts as a suction to stop the lungs from collapsing
53
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
54
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 SA
* The diffusion capacity of the gas
And inversely proportional to:
* The thickness of the exchange surface
55
Increasing what factors of Fick's law will increase the rate of diffusion?
Concentration gradient, surface area, diffusion capacity
56
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
57
What does Boyle's law state?
At the constant temperature, the volume of a gas is inversely proportional to the pressure of the gas
58
What does Charles' law state?
At a constant pressure, the volume of gas is proportional to the temperature of the gas
59
What percentage of the air is oxygen?
20.95%
60
What percentage of the air is nitrogen?
78.09%
61
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
62
What happens to the proportion of oxygen in the air when a patient is under oxygen therapy?
Increased O2 partial pressure
Other gases stay the same
63
How does the composition of air being breathed in change when a patient is in a house fire?
Decreased O2 partial pressure
Increase in CO2 and CO partial pressure
64
How does the composition of air being breathed in change when a person is at high altitudes?
Composition doesn't change but the volume of each gas inhaled decreases
65
What four things happen to air as it passes down the respiratory tree?
Warmed, humidified, slowed and mixed
66
What do haemaglobin monomers consist of?
Ferrous iron ion at the center of a porphyrin ring, connected to a protein chain, covalently bonded at the proximal histamine residue
67
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
68
Between a bound and unbound haemaglobin, which has a higher affinity for oxygen?
Bound
69
In oxygen rich areas, what is promoted?
Oxygen loading
70
In what circumstance is oxygen unloading promoted?
In oxygen starved areas as haemaglobin has a lower affinity for O2
71
What shape is the oxygen dissociation curve?
Sigmoidal
72
What causes a **rightward** shift in the oxygen dissociation curve? (HAHI)
* Higher temperature
* Acidosis – increased H+ ions
* Hypercapnia – increased CO2 concentration in blood (affects COPD patients)
* Increased 2,3-DPG
73
What change in oxygen affinity is a rightwards shift associated with?
**Decreased** oxygen affinity of haemoglobin
74
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
75
What happens to the oxygen carry capacity when there is a downwards shift in the oxygen dissociation curve?
Decreased oxygen carry capacity
76
What happens to the oxygen carry capacity when there is a upwards shift in the oxygen dissociation curve?
Increased oxygen carrying capacity
77
What conditions results in a decreased oxygen carrying capacity?
Anaemia
78
What condition results in an increased oxygen carry capacity for haemoglobin?
Polycythaemia
79
What is the oxygen affinity of foetal haemoglobin relative to adult haemoglobin?
Higher affinity
80
Why does HbF have a higher affinity for oxygen than HbA?
So it can extract oxygen from the mothers blood in placenta
81
At what point is foetal haemoglobin completely replaced by adult haemoglobin?
6 months after birth
82
What is a treatment of sickle cell disease involving foetal Hb?
HbF production can be pharmacologically induced in adults to treat SCD
83
Describe the allosteric behaviour of Haemoglobin?
Once more oxygen molecules have bound to Hb, 2,3-DPG is more likely to bind which helps the unloading of oxygen
2,3-DPG is a metabolic product, thus is found at sites where more respiration occurs and more oxygen is needed
84
What does allosteric mean?
Changes shape when something binds
85
What affect does CO have on the oxygen dissociation curve?
Downwards and leftwards shift
86
What does the downwards and leftwards shift of the oxygen dissociation curve shown by CO represent?
Decreased capacity but increased affinity
I.e. there are less binding sites available, but the O2 that does bind does so more strongly and is less easily released
87
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
88
Where is myoglobin found?
In skeletal muscle tissue
89
Why is myoglobin not capable of cooperative binding?
It is made of a single polypeptide with only one heme group
90
What shape is the oxygen dissociation curve for myoglobin?
Logarithmic
91
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
92
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
93
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
94
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
95
What is external respiration a result of?
Partial pressure gradients, alveolar surface area and ventilation and perfusion matching
96
What is the partial pressure of oxygen in the oxygenated blood of the capillary after oxygen loading?
100mmHg
97
What is the partial pressure gradient of oxygen?
60mmHg
98
What is the partial pressure gradient for carbon dioxide?
5mmHg
99
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
100
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
101
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
102
What does a severe ventilation-perfusion mismatch indicate?
Severe lung disease
103
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
104
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
105
What properties of carbon dioxide make it good at being transported?
* More soluble in the blood than oxygen
* It binds to plasma proteins or can enter red blood cells and bind to haemoglobin quite easily
106
What is formed when carbon dioxide binds to haemoglobin?
Carbaminohaemoglobin
107
How are the majority of carbon dioxide molecules carried around the blood?
By the bicarbonate buffer system
108
What enzyme is used within the red blood cells to convert the carbon dioxide into carbonic acid (H2CO3)
Carbonic anhydrase
109
What does carbonic acid dissociate into?
Bicarbonate ions and hydrogen ions
110
What allows for the continued uptake of carbon dioxide into the blood?
The fact that carbon dioxide is very quickly converted into bicarbonate ions
111
How is the change in pH which could arise from excess H+ ions avoided?
Haemoglobin binds to the free H+ ions
112
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
113
When is the bicarbonate ion shuttled back into the RBC in exchange for the chloride ion during the chloride shift?
When the blood reaches the lungs
114
How is the carbonic acid intermediate reformed?
The bicarbonate ion binds to the H+ ion which has dissociated from the haemoglobin
115
How does carbon dioxide bind to haemoglobin?
It binds to the amine group of the haemoglobin molecule
116
What is the benefit of the bicarbonate buffer system?
* Carbon dioxide is dissolved in blood with no change to the pH of the system
* 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
117
What is the pulmonary transit time?
0.75 seconds
118
What part of the 0.75 seconds of pulmonary transit time does diffusion occur in?
The first 0.25 seconds
119
What happens in the last 0.5 seconds of the pulmonary transit time?
It is the reserve time – so when diffusion is impaired, the reserve time is needed for diffusion to be complete
120
What happens to the transit time and reserve time when we exercise?
Transit time decreases and reserve time also gets shortened
121
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
122
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
123
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.
124
What is hypercapnia?
High CO2
125
Why would increased tidal volume increase the concentration of dissolved oxygen in the blood?
Deeper breathing increases the 'refresh rate' of air at the gas exchange surfaces, which is important for regulating CO2
