Week 1- Respiratory Physiology Flashcards
(260 cards)
1
Q
What is the average lung volume?
A
6L
2
Q
What is the volume of air taken in on an average inspiration?
A
2.8L
3
Q
Define “tidal volume”
A
the volume of air that you breathe in and out at rest
4
Q
What is the average tidal volume?
A
500ml
5
Q
Explain what is meant by the term “functional residual capacity”
A
The residing volume of air still in our lungs at the end of a normal relaxed expiration
6
Q
What is the average functional residual volume?
A
2.3L
7
Q
Define the term “inspiratory reserve” and state the average respiratory reserve volume.
A
If we take a really big breath and take in as much air as we can on top of our normal tidal volume, we can take in an additional 3L of air; this is our inspiratory reserve.
8
Q
What is meant by the term “expiratory reserve?” State the average respiratory reserve in L
A
- Our expiratory reserve volume is the extra air that we can exhale on top of a normal exhalation (exhale normally then force further air out of the lungs. On average this is around 1L of air)
9
Q
What is “vital capacity”?
A
the maximum amount of air that we can voluntarily expire after a maximum inspiration
10
Q
What can vital capacity be used to measure?
A
Lung function
11
Q
What is the difference between a capacity and a volume?
A
A capacity is made up of 2 or more different volumes added together.
12
Q
Which capacities are added together to make the vital capacity?
A
inspiratory reserve volume + tidal volume + expiratory reserve volume.
13
Q
Which capacities are added together to make the total lung capacity?
A
vital capacity + the residual volume
14
Q
Which capacities are added together to make the inspiratory capacity?
A
tidal volume + inspiratory reserve volume.
15
Q
Which capacities are added together to make the functional residual capacity?
A
expiratory reserve volume + residual volume.
16
Q
If we expire as hard as we can, is it possible to empty the residual volume?
A
No
17
Q
Explain why the residual lung volume cannot be forcibly expired
A
Because it plays the following 2 important roles;
- It stops the alveoli from collapsing (this is a means of saving energy because it would take a LOT more effort to inflate collapsed alveoli). Alveoli never fully collapse they just vary in the degree of their expansion.
- Residual volume provides a volume of air that allows gas exchange to continue to take place in between breaths
18
Q
What volume of fluid is contained within the pleural cavity?
A
3ml
19
Q
Name the two components of the pleura
A
Parietal pleura & visceral pleura
20
Q
Where would you find the parietal pleura?
A
Stuck to the ribs & chest wall
21
Q
Where would you find the visceral pleura?
A
The lung surface
22
Q
Are the parietal and visceral pleura two separate membranes?
A
No they are continuous with each other at the hilum
23
Q
What is the function of the pleura?
A
To adhere the lung to the chest wall and to allow smooth movement between the lungs and the chest wall
24
Q
What drives the recoil of the chest wall during expiration?
A
Elastic Recoil
25
Is expiration a active or passive process?
Passive (except in disease)
26
What is the hilum of the lungs?
The hilum is the point at which the bronchi, blood vessels and other structures enter and leave the lungs
27
What does Boyle's law state?
the pressure exerted by a gas is inversely proportional to its volume. Gases (singly or in mixtures) move from areas of high pressure to areas of low pressure
28
What does Dalton's law state?
the total pressure of a gas mixture is the sum of the pressures of the individual gases.
29
What does henry's law state?
the amount of gas dissolved in a liquid is determined by the pressure of the gas and it’s solubility in the liquid.
30
What does Charles' law state?
the volume occupied by a gas is directly related to the absolute temperature
31
What happens to the pressure inside the chest when the volume increases (inspiration)
The pressure decreases (which helps to draw air into the lungs)
32
What happens to the pressure inside the chest when the volume decreases (on expiration)
The pressure increases (which helps to move air out of the lungs and back into the atmosphere)
33
What are the normal muscles of inspiration?
external intercostals muscles and the diaphragm
34
What are the normal + accessory muscles of inspiration?
external intercostals muscles, the diaphragm, the scalene and the sternocleidomastoid
35
What are the accessory muscles of expiration (remember that expiration is a passive process in healthy individuals)
internal intercostal and abdominal muscles
36
What nerve causes contraction (flattening) of the diaphragm?
The phrenic nerve
37
Is air resistance greater during inspiration or expiration? Explain the answer.
during inspiration the airways get stretched open. Therefore, air resistance is less during inspiration than it is during expiration
38
What action do the external intercostal muscles have upon the sternum?
They raise the sternum which increases the dimensions of the anterior and posterior thoracic cavity
39
What actions do the external intercostals exert on the ribs?
They cause them to raise in an outwards and upwards movement which increases the lateral dimension of the ribcage
40
What action do the internal intercostals have on the sternum?
They bring the sternum down which decreases the dimensions of the anterior and posterior cavity
41
What actions do the internal intercostals exert on the ribs?
Move the ribcage downwards and inwards which decreases the lateral dimension of the ribcage
42
Define "intra-thoracic (alveolar) pressure"
The pressure inside the thoracic cavity, (essentially pressure inside the lungs).
43
Is intra-thoracic pressure positive or negative?
pressure may be negative (less than atmospheric pressure) at the start of inspiration or positive (more than atmospheric pressure) at the start of expiration.
44
What is intra-pleural pressure?
The pressure inside the pleural cavity
45
Is intra pleural pressure positive or negative?
Negative
46
What is trans pulmonary pressure?
the difference between alveolar pressure and intra-pleural pressure
47
Is trans pulmonary pressure positive or negative?
It is almost always positive because Pip is negative (in health). PT = Palv – Pip.
48
What two things determine lung volume?
1. Transpulmonary pressure
| 2. Elastic capacity of the lungs
49
What does airway resistance determine?
how much air flows into the lungs at any given pressure difference between atmosphere and alveoli.
50
What is airway resistance determined by?
The radii of the airways
51
When is alveolar pressure the same as atmospheric pressure?
When the air movement has stopped
52
Describe a lung pressure of 0 and of +ve 4 in relation to atmospheric pressure
The pressure inside the lungs is measured in comparison to atmospheric pressure. Therefore, if the reading is 0, it means that the pressure is the same as atmospheric pressure. If the reading is +ve 4, then the pressure is 4 millilitres higher than atmospheric pressure.
53
Why is intrapleural pressure always less than alveolar pressure?
The intrapleural pressure is generated between the chest wall and the lungs. The chest wall drives inspiration and elastic recoil drives expiration. The muscles that act upon the chest wall means that the chest wall always wants to expand so the cavity is always trying slightly to expand and increase in volume. Because it always wants to increase in volume, it is always negative (remember as you increase in volume, you decrease in pressure).
54
Which cell type produces surfactant?
Type 2 pneumocytes
55
What is the role of surfactant/
reduces surface tension on the alveolar surface membrane, thus reducing the tendency for alveoli to collapse
56
What is surface tension?
the attraction between water molecules which occurs when there is an air-water interface
57
Other than reducing surface tension, that other three functions does surfactant have?
* Increases lung compliance
* Reduces the lungs tendency to recoil
* Makes the work of breathing easier
58
What is the law of LaPlace?
the pressure required to keep an alveoli open is 2x the surface tension divided by the radius.
59
Is the pressure required to keep an alveoli open greatest in bigger alveoli or in smaller alveoli?
smaller alveoli
60
Why is maintaining the inflation of smaller alveoli is more beneficial than maintaining the inflation of larger alveoli?
smaller alveoli have a bigger surface area to volume ratio
61
When does surfactant production occur in utero?
starts at 25 weeks’ gestation and is complete by 36 weeks
62
What is the production of surfactant in utero stimulated by?
thyroid hormones and cortisol
63
Briefly describe the physiology of Infant Respiratory Distress Syndrome
Babies born prematurely before 36 weeks’ gestation must overcome surface tension caused by a lack of surfactant and essentially fight to stop their alveoli from collapsing. This requires a colossal energy requirement. This is the reason that premature babies become exhausted very quickly
64
What can be administered to a premature baby after birth to help manage respiratory distress?
Aerosol Surfactant
65
What is the difference between lung compliance and lung elasticity?
Compliance is the lung stretching outwards when you breathe in, elasticity is the lung recoiling when you breathe out
66
Which three factors determine compliance?
Elastic forces, surface tension at the alveolar air-liquid interface and by airway resistance.
67
What happens to compliance in emphysema and why is a bad thing?
Emphysemic lungs have high compliance BUT they have low elasticity. High compliance is only a good thing if it is accompanied by high elasticity
68
Explain low compliance
a small increase in lung volume for a large decrease in intrapleural pressure.
Low compliance means you have to work very hard to get air into the lungs.
69
Name a pathology that causes low compliance
Fibrosis
70
Explain high compliance
a large increase in lung volume for a small decrease in intrapleural pressure (healthy lungs have high compliance)
71
What happens to compliance as we age?
Lungs loose compliance
72
What impact does surfactant have upon compliance
Surfactant increases compliance
73
What is a normal, average tidal volume volume?
500ml
74
What is a normal, average residual volume volume?
1200ml
75
What is a normal, average expiratory reserve volume?
1100ml
76
What is a normal, average inspiratory reserve volume??
3000ml
77
What is a normal, average vital capacity volume?
4600ml
78
What is a normal, average total lung capacity volume?
6L
79
What is the volume of the anatomical dead space?
150ml
80
What is ventilation?
The movement of air in and out of the lungs (breathing)
81
What is pulmonary/minute ventilation?
The total air movement in and out of the lungs
82
What is alveolar ventilation?
The volume of fresh air getting to alveoli and therefore available for gas exchange
83
Explain the impact of the anatomical dead space on alveolar ventilation
1. Upon expiration, the first air to be expelled is the 150ml sitting in the dead space. 500ml of air is pushed out of the lungs on expiration but only 350ml leaves the respiratory system completely. 150ml remains behind in the dead space.
2. During the next inhalation, the 150ml of air in the dead space is the first to move down into the lungs. This is followed by 500ml of ‘fresh air’ however only 350ml of this 500ml reaches the lungs because 150ml is left behind in the dead space.
3. And repeat
This means that breathing is only ever 70% effective
84
How can we change our alveolar ventilation?
our dead space volume is fixed but our lung capacity can vary enormously. We can therefore, change our alveolar ventilation by altering our breathing pattern
85
Should the term hyperventilation not be used to describe somebody that is breathing very fast
Their breathing rate may be fast but this means that their tidal volume will be low. The amount of air reaching the alveoli is therefore less so they are HYPOventilating
86
How can be pulmonary ventilation be calculated?
Respiratory rate x tidal volume
87
How can alveolar ventilation be calculated?
[Tidal volume-dead space volume] x respiratory rate
88
What is the normal alveolar partial pressure (and therefore systemic arterial PP) of O2 (in mmHg and kPa)
100mmHg (13.3 kPa).
89
What is the normal alveolar partial pressure (and therefore systemic arterial PP) of CO2 (in mmHg and kPa)
40mmHg (5.3kPa).
90
What happens to PO2 and PCO2 in hyperventilation?
- During hyper-ventilation (increased alveolar ventilation) PO2 rises to about 120 mm Hg and PCO2 falls to about 20 mmHg.
91
What happens to PO2 and PCO2 in hypoventilation?
- During hypo-ventilation (decreased alveolar ventilation) PO2 falls to 30 mmHg and PCO2 rises to 100 mmHg
92
What is the partial pressure of oxygen in the atmosphere?
160mmHg
93
Why is the partial pressure of oxygen in the alveoli lower than the partial pressure of oxygen in the atmosphere?
the air becomes diluted by The air in the anatomical dead space and the residual volume. It also becomes saturated with water. This causes the reduction in the partial pressure of O2
94
What happens to breathing rate when PaCO2 begins to rise and why?
- As carbon dioxide levels creep up, centres in the brain that make us breathe are stimulated.
- Humans are hypersensitive to changes in CO2. Too much CO2 is toxic to our cells, but not enough CO2 will stop stimulating our breathing centres and we become apnoeic
95
Where in the lung is alveolar ventilation greatest and worst?
greatest at the base of the lung and worst at the apex due to changes in compliance throughout the lung.
96
Where in the lung is compliance lowest and why?
Compliance is lower at the apex because the lungs are hanging in the thoracic cavity & the weight of the lungs causes alveoli at the apex to be open while alveoli at the base are slightly squashed by the weight of the lungs and the diaphragm. Therefore, there is much more capacity for the alveoli at the base to expand because those at the apex are already stretched open (and therefore don’t have much space to expand any further).
97
The pulmonary artery carries ______ blood ____ from the ______ to the ______
The pulmonary artery carries deoxygenated blood AWAY from the heart to the lungs.
98
The pulmonary vein carries _________ blood __________ the _______ from the _________
The pulmonary artery carries deoxygenated blood AWAY from the heart to the lungs.
99
What are the two branches of the pulmonary circulation?
Bronchial circulation (blood supply to the lungs)
Pulmonary circulation (gas exchange)
100
What is the blood pressure like in the pulmonary circulation compared to the systemic circulation?
The pulmonary circulation is a high flow, low pressure system: (the blood pressure is around 25/10mmHg vs the systemic circulation which has a pressure of around 120/80mmHg).
101
Name the two places that gas exchange occurs
1. Between the pulmonary circulation and the alveoli
| 2. Between the systemic circulation and the tissues
102
What is the partial pressure of oxygen in the tissues?
40mmHg
103
Why is the pressure gradient of oxygen between the blood (100mmHg) and the tissues (40mmHg) so important?
It creates a gradient and facilitates the movement of oxygen into the tissue
104
What is PaO2
partial pressure of oxygen in arterial blood
105
What is PAO2?
partial pressure of oxygen in alveolar air
106
What is the rate of gas diffusion across a membrane directly proportional to?
- The partial pressure gradient
- Gas solubility
- The available surface area
107
What is the rate of gas diffusion across a membrane directly inversly proportional to?
The thickness of the membrane
108
What are the diffusion rates of oxygen and CO2?
```
oxygen = 250ml/min
CO2= 200ml/min
```
109
Which is more soluble in water; O2 or CO2?
CO2 is FAR more soluble in water than O2
110
What is spirometry used to measure?
Lung function
111
Which lung volumes and capacities can be measured with spirometry?
Remember if you can’t expire it, spirometry can’t measure it!
- Tidal volume
- Expiratory reserve volume
- Inspiratory reserve volume
- Inspiratory capacity
- Vital capacity
112
What is FEV1?
the amount of air that can be forcibly exhaled in 1s from your lungs after taking the deepest breath possible
113
What is FVC?
the total volume of air that can be forcibly exhaled from the lungs after taking in the deepest breath possible (in however long it takes).
114
What is the average FVC of a fit, healthy young adult male?
5.0L
115
What is a normal healthy FEV1/FVC ratio?
80%
116
What happens to the FEV1/FVC ratio in obstructive disease?
Unproportional decreases in FEV1 and FVC
117
What happens to the FEV1/FVC ratio in restrictive disease? 9overall ratio is decreased)
Proportional decreases in FEV1/FVC (so the overall ratio s unchanged)
118
Which type of lung diseases (obstructive or restrictive) is spirometry good at diagnosing?
useful at diagnosing obstructive lung diseases.
| not useful for diagnosing restrictive lung diseases because it gives a normal ratio
119
What is the difference between compliance and elasticity?
compliance is how stretchy the lungs are on inspiration while elasticity is how much recoil the lungs have on expiration
120
What happens to compliance as you move through inspiration and why?
At the start of inspiration, you need quite a big decrease in intrapleural pressure before you see a change in lung volume, therefore, complience increases as you move through the inspiratory phase.
121
What happens to compliance as you move through expiration and why?
On expiration, compliance is low at the start and very little air moves out of the lungs. Compliance increases significantly and much more air is expired once intrapleural pressure has fallen. Compliance therefore decreases as you move through the expiratory phase.
122
Do obstructive diseases increases the work of inspiration or expiration?
Obstructive diseases increase the work of expiration
123
Do restrictive diseases increases the work of inspiration or expiration?
Restrictive diseases increase the work of inspiration
124
What is lung inertia?
the lung not wanting to change shape
125
What must be overcome during inspiration?
Lung inertia
126
What must be overcome during expiration?
Surface tension
127
Define ventilation
The amount of fresh air getting to the alveoli to engage in gas exchange(L/min)
128
Define perfusion
The blood flow through the pulmonary circulation (L/min)
129
If ventilation and perfusion matched perfectly, then the ventilation/perfusion ratio (sometimes called V/Q) would be ___.
1
130
How do you calculate the ventilation perfusion ratio?
ventilation divided by perfusion (V/Q)
131
What happens to blood flow and ventilation from the apex to the base of the lung and why?
From the apex to the base the ventilation and blood flow decrease due to changes in compliance
132
What causes the small V/Q mismatch at the base of the lungs?
Blood flow is higher than ventilation because arterial pressure exceeds alveolar pressure. This compresses the alveoli.
133
What are the two ways in which V/Q can be mismatched?
1. Ventilation is less than perfusion
| 2. Ventilation exceeds perfusion
134
What is the ventilation perfusion ratio going to be when ventilation is less than perfusion?
less than 1
135
What is the ventilation perfusion ratio going to be when ventilation exceeds perfusion?
>1
136
Where in the lung is there a significant ventilation/perfusion mismatch that is physiologically normal?
At the apex of the lung
137
What physiological process happens when perfusion exceeds ventilation and why?
Shunt (pulmonary vasoconstriction and bronchial dilation occurs to redirect the blood flow away from an area that is poorly ventilated)
138
What happens when ventilation exceeds perfusion?
“Alveolar dead space” (not enough blood passing by the alveoli for gas exchange so the air in the alveoli isn’t used and is therefore “dead air”)
139
What is physiological dead space?
Anatomical dead space + alveolar dead space
140
What is respiratory sinus arrhythmia?
the natural quickening of your pulse upon inspiration and the natural slowing of your pulse upon expiration.
141
Why does respiratory sinus arrhythmia occur?
If heart rate always stayed constant, during inspiration we would have increased alveolar dead space and upon expiration we would have increased shunt.
Respiratory sinus arrhythmia therefore ensures that the ventilation/perfusion ratio stays as close to 1 as possible (matched)
142
What causes respiratory sinus arrhythmia?
Increased vagal activity during expiration
143
Describe the partial pressure of O2 and CO2 at each point;
1. Dry inspired air
2. Humidified Tracheal Air
3. alveolar Air
4. Systemic Arterial Blood
5. resting tissue
6. Systemic Mixed venous Blood
1. Dry inspired air (PO2 = 160, PCO2= 0)
2. Humidified Tracheal Air (PO2= 150, PCO2= 0)
3. alveolar Air (PO2= 100, 0CO2= 40)
4. Systemic Arterial Blood (PO2= 100, PCO2= 40)
5. Resting Tissue (PO2= 40, PCO2= 46)
6. Systemic Mixed venous Blood (PO2= 40, PCO2= 46)
144
What is the rate of gas diffusion proportional to?
The partial pressure of the gas
145
How does oxygen travel in the blood?
1. Bound to haemoglobin
| 2. In solution in plasma
146
How may ml of oxygen are carried per litre of whole blood?
200ml
147
If the 200ml of oxygen carried in 1L of whole blood, how many ml are carried in plasma and how many ml are carried by haemoglobin?
Dissolve in Plasma= 3ml
| Bound to haemoglobin= 197ml
148
How is CO2 transported in blood?
The majority of CO2 (77%) is transported in solution in plasma. Only 23% of CO2 is transported in haemoglobin.
149
Why is oxygen carried by haemoglobin rather than just dissolving in plasma?
It is not very soluble
150
How may molecules of oxygen can each haemoglobin bind?
4
151
What element is utilised by haemoglobin?
Fe2+
152
Explain the concept of cooperative binding
When the first oxygen molecule binds to haemoglobin, it causes haemoglobin’s polypeptide chains to reshuffle slightly to make it easier for the other 3 oxygen molecules to bind. Similarly, when oxygen leaves the haemoglobin, the polypeptide chains reshuffle again making it harder for any more oxygens to bind.
153
How long is the arterial blood in contact with the alveoli and how long does it take dot haemoglobin to saturate?
Arterial blood is usually in contact with the alveoli for around 0.75 seconds but haemoglobin is fully saturated after 0.25 seconds of contact.
154
Name three causes of anaemia
1. iron deficiency
2. Haemorrhage
3. Vitamin B12 deficiency
155
Does the partial pressure of oxygen change in the blood of an anaemic patient? Explain why
The partial pressure only accounts for the oxygen that is in solution (not the oxygen attached to haemoglobin).
Anaemia is caused by the reduced carrying capacity of haemoglobin therefore overall, an anaemic patient will have less oxygen in their blood but their partial pressure will be unchanged
156
What is meant by the "partial pressure of oxygen"?
REMEMBER THAT THE PARTIAL PRESSURE OF OXYGEN IS THE AMOUNT OF OXYGEN IN SOLUTION (THE OXYGEN BOUND TO HAEMOGLOBIN DOES NOT COUNT!)
157
What happens to the affinity of haem groups for oxygen when PO2 falls below 60mmHg?
The affinity of the haem groups for oxygen begins to decrease.
158
How much oxygen does haemoglobin give up to resting tissue to meet the resting energy demand?
25% (1 oxygen molecule out of the 4 it is carrying)
159
name 4 factors that cab affect the affinity of oxygen for haemoglobin and therefore disrupt the oxygen/haemoglobin dissociation curve
1. PH
2. Partial pressure of CO2
3. temperature
4. Diphosphoglycerate
160
What impact does alkalosis have on the oxygen-haemoglobin dissociation curve?
shifts curve to the left (affinity of haemoglobin for oxygen is decreased)
161
What impact does acidosis have on the oxygen-haemoglobin dissociation curve?
Shifts curve to the right (affinity of haemoglobin for oxygen is increased)
162
What impact does hypocapnia have on the oxygen-haemoglobin dissociation curve?
Shifts curve to the left (affinity of haemoglobin for oxygen is decreased)
163
What impact does hypercapnia have on the oxygen-haemoglobin dissociation curve?
shifts curve to the right (affinity of haemoglobin for oxygen is increased)
164
What impact does hypothermia have on the oxygen-haemoglobin dissociation curve?
Shifts curve to the left (affinity of haemoglobin for oxygen is decreased)
165
What impact does hyperthermia have on the oxygen-haemoglobin dissociation curve?
Shifts curve to the right (affinity of haemoglobin for oxygen is increased)
166
What impact does low diphosphoglycerate have on the oxygen-haemoglobin dissociation curve?
shift the curve to the left (affinity of haemoglobin for oxygen is decreased)
167
What impact does high diphosphoglycerate have on the oxygen-haemoglobin dissociation curve?
shift the curve to the right (affinity of haemoglobin for oxygen is increased)
168
What is the Bohr effect?
the shifting of the oxygen-haemoglobin dissociation curve to the right. It aides oxygen unloading at the peripheral tissues by reducing the affinity of haemoglobin for oxygen.
169
Explain why carbon monoxide is so dangerous
binds to haemoglobin to form carboxyhaemoglobin with an affinity 250 times greater than O2 - binds readily and dissociates very slowly so very problematic once dissolved in circulation.
170
List the clinical signs of carbon monoxide poisoning
hypoxia, anaemia, nausea, headache, cherry red skin and mucous membranes
171
What would be the expected respiratory rate in carbon monoxide poisoning?
Respiratory rate is unaffected in carbon monoxide because of the normal PCO2
172
How is CO poisoning treated?
100% oxygen to increase PaO2
173
What happens when CO2 molecules diffuse from the tissues into the blood?
7% remains dissolved in plasma and erythrocytes
23% combines in the erythrocytes with deoxyhemoglobin to form carbamino compounds
70% combines in the erythrocytes with water to form carbonic acid, which then dissociates to yield bicarbonate and H+ ions.
174
What happens to the bicarbonate ions formed by CO2 after it is released from tissues into the blood?
Bicarbonate moves out of the erythrocytes into the plasma in exchange for Cl- ions & the excess H+ ions bind to deoxyhemoglobin
175
Name the enzyme that converts carbon dioxide to carbonic acid and bicarbonate ions and back again. Where is this enzyme found.
carbonic anhydrase (found in red blood cells)
176
Explain why arterial partial pressure of O2 (PaO2 ) is not the same as arterial O2 concentration/content
PaO2 refers purely to O2 in solution
Arterial O2 content includes O2 in solution AND O2 bound to haemoglobin
177
Why must gases travel in solution or bound to haemoglobin?
they cannot travel as a gas because this would cause an air embolism and death
178
Name the three different types of haemoglobin
1. HbA2 (δ chains replace β)
2. HbF= foetal haemoglobin (γ chains replace β)
3. Glycosylated Hb (HbA1a, HbA1b, HbA1c)
179
Which type of haemoglobin makes up 92% of the haemoglobin in our bodies?
HBA
180
What causes glycosylated haemoglobin?
Haemoglobin becomes glycosylated when it is exposed to high levels of glucose
181
what can glycosylated haemoglobin be used to measure?
Control of blood sugar in diabetic patients over a 3 month period
High levels of glycosylated haemoglobin= poor control of blood sugars and multiple hyperglycemic attacks.
182
Why do HBF (foetal haemoglobin) and myoglobin have a higher affinity for haemoglobin than HBA?
to extract O2 from maternal/arterial blood.
183
What is myoglobin and where can it be found?
Myoglobin is another oxygen carrier & oxygen storage molecule, found exclusively in cardiac and skeletal muscle.
184
What is myoglobin in the blood indicative of?
Tissue damage (myoglobin should not be found in the blood!)
185
How does myoglobin's affinity for oxygen compare to HBA's?
Myoglobin has a much higher affinity for oxygen than haemoglobin
186
List the 5 different types of hypoxia
1. Hypoxaemic hypoxia
2. Anaemic hypoxia
3. Stagnant hypoxia
4. Histotoxic hypoxia
5. Metabolic hypoxia
187
What is the most common type of hypoxia
Hypoxaemic hypoxia
188
What is hypoxaemic hypoxia?
Reduction in O2 diffusion at lungs either due to decreased PO2atmos or tissue pathology.
189
What is anaemic hypoxia?
Reduction in O2 carrying capacity of blood due to anaemia (red blood cell loss/iron deficiency).
190
What is stagnant hypoxia?
Heart disease results in inefficient pumping of blood to lungs/around the body
191
What is histotoxic hypoxia?
poisoning prevents cells utilising oxygen delivered to them e.g. carbon monoxide/cyanide
192
What is metabolic hypoxia?
oxygen delivery to the tissues does not meet increased oxygen demand by cells.
193
What are the skeletal muscles involved in ventilatory control innervated by?
Somatic motor neurone (we have control over them!)
194
Explain what drives the skeletal muscles of respiration when we are not consciously thinking about it
Centres in the brainstem control the phrenic (to diaphragm) and intercostal nerves (to external intercostal muscles) which stimulate the skeletal muscles to facilitate inspiration.
195
which part of respiration is passive at rest (and therefore requires no neural input)
Expiration
196
Where are the areas of ventilation control in the brain/
Brainstem (pons and medulla)
197
Severing the spinal cord at what level would cause cessation of breathing and why?
C3 (because this is the origin of the phrenic nerve)
198
Name 4 factors that can influence the neural control of respiration
Chemoreceptor input
Emotional impulses from the limbic system
Voluntary control from higher brain centres
Mechanosensory receptor input
199
Name the two different types of chemoreceptor involved in respiration
1. Central chemoreceptors
| 2. peripheral chemoreceptors
200
Where are central chemoreceptors and what do they respond to?
Location: Medulla
| Respond to: H+ in the CSF around the brain (which originate from PCO2)
201
Which chemoreceptors are responsible for primary ventilatory drive
Central Chemoreceptors
202
Where are peripheral chemoreceptors and what do they respond to?
Location: Carotid and Aortic bodies
| Respond to: PO2
203
What happens to respiration when central chemoreceptors detect a rise in H+ (raised PCO2)
Ventilation is stimulated
204
What causes the central chemoreceptors to inhibit ventilation?
a decrease in arterial PCO2
205
explain why individuals with chronic lung disease can become reliant on peripheral chemoreceptors instead of central chemoreceptors
central chemoreceptors of these individuals become desensitised to PCO2 and the individual instead begins to rely on changes in PaO2 to stimulate ventilation (detected by the peripheral chemoreceptors). This is called “Hypoxic Drive”
206
WhatmmHg must PO2 drop below before peripheral chemoreceptors are stimulated?
60mmHg
207
Why doesnt the respiration rate of anaemic patients increase?
If the lungs are working normally, diffusion will take place normally and therefore the amount of oxygen in solution in the plasma (PaO2) will be normal.
As PaO2 is what the peripheral receptors monitor there will be no increase in RR.
208
Explain the effects of barbiturate and opioid analgesics on respiration
Barbituates and opioids depress the respiratory centres by decreasing their sensitivity to pH (which is controlled primarily by the CO2/bicarbonate buffer system)
209
Explain the effects of nitrous oxide (an analgesic) on peripheral chemoreceptors. When would these effects be problematic/
blunts the peripheral chemoreceptor response to falling PaO2.
Not problematic in most people because peripheral chemoreceptors are responsible for secondary ventilatory drive. In those with a chronic lung disease running off hypoxic drive. in these individuals, central chemoreceptors are desensitised and peripheral chemoreceptors are therefore responsible for primary ventilatory drive. Giving these patients NO will leave them with no control over their respiratory drive
210
What is the main factor which determines ventilation?
The chemical composition of plasma (controlled mainly by PCO2)
211
Which two systems are responsible for the acid/base balance in blood?
The renal and respiratory system
212
What is normal blood pH?
7.4
213
Can H+ ions cross the blood brain barrier?
NO
214
What happens to ventilation in acidosis (reduced blood pH?)
Ventilation increases
215
What happens to ventilation in alkalosis (increased blood pH?)
Ventilation decreases
216
What happens to H+ levels in hypoventilation? (remember hypoventilation is NOT breathing slowly!!)
Hypoventilation, causing CO2 retention, leads to increased [H+] bringing about respiratory acidosis.
217
What happens to H+ in hyperventilation? (remember hyperventilation is NOT 'breathing fast")
Hyperventilation, blowing off more CO2, lead to decreased [H+] bringing about respiratory alkalosis
218
How does exercising affect the acid base balance of blood?
The release of lactic acid from exercising muscle into blood causes metabolic acidosis
219
Explain why hyperventilation can occur during exercise
During very strenuous exercise, ventilation increases more than metabolism. Arterial [H+] increases because of increased lactic acid production. This accounts for some of the hyperventilation seen in this situation.
220
Explain what happens to PO2 and PCO2 when you hold your breath and the affect this has on the body
Prolonged breath holding results in decreased PO2 and increased PCO2. This eventually causes a loss of consciousness at which point the individual loses voluntary control over breathing and the body initiates breathing.
221
Explain how the respiratory system facilitates safe swallowing
Respiration is inhibited during swallowing to avoid aspiration of food or fluids into the airways. Swallowing is followed by an expiration in order that any particles are dislodged outwards from the region of the glottis.
222
What are the 4 main functions of the respiratory system?
1. Gas exchange
2. Acid base balance
3. Protection from infection
4. Communication & speech
223
What is external respiration?
breathing & gas exchange
224
What is internal respiration?
Cellular respiration
225
List the three points of gas exchange in the body
1. Gas exchange between the atmosphere and the lung
2. Gas exchange between the lung and the blood
3. Gas exchange between the blood and the cells
226
What is the difference between the systemic and the pulmonary circulatory system?
Systemic circulation = the system that goes all around the body. The systemic circulatory system delivers O2 to the peripheral tissues and collects CO2
The pulmonary circulation= the specialised circulatory system that only travels between the heart and the lungs
227
Which pulmonary vessels carry A) Oxygenated blood & B) Deoxygenated blood
A) pulmonary vein carries oxygenated blood.
B) pulmonary artery carries deoxygenated blood
228
What are the anatomic definitions of an artery and a vein?
Artery = “a vessel carrying blood away from the heart”
vein = “a vessel carrying blood towards the heart”.
229
In the steady state, what is the net volume of eO2 and CO2 exchanged in the lungs per unit time
250ml/min O2
| 200ml/min CO2
230
Why is it more comfortable to breathe through the nose than through the mouth?
the nose is better at warming and moistening air due to its larger surface to volume ratio.
231
Why must air be fully saturated with water before it reaches the deepest part of the lung?
If air is not in solution, it cannot diffuse
232
What is the pharynx?
the throat
233
Where is the epiglottis located?
Between the pharynx and the larynx
234
Where does the trachea begin?
After the larynx
235
Where does the trachea divide?
Sternal angle (T4)
236
How many secondary bronchi are there on the left and on the right?
```
L= 2 (to supply the 2 lobes)
R= 3 (to supply the 3 lobes)
```
237
What structures make up the upper respiratory tract?
The larynx and everything above
238
What structures make up the lower respiratory tract?
The trachea and everything below
239
How much air is in the dead space?
150ml
240
Name the lobes of the right lung
superior, middle and inferior lobes
241
What fissures split the right lung?
Horizontal and oblique
242
What fissure splits the left lung?
Oblique
243
Name the lobes of the left lung
Superior and inferior
244
Why has the left lung got 2 lobes while the right lung has 3 lobes?
The left lung is smaller because more space on this side is occupied by the heart
245
What supplies each segment of lung?
A tertiary bronchus
246
There is no cartilage in the tertiary bronchi. What keeps it patent?
Physical forces acting within the thorax
247
At what point to bronchi become bronchioles?
At the point where the cartilage is lost
248
In which primary bronchus are aspirated foreign objects more likely to become lodged and why?
The right- it is wider and straighter
249
is airflow resistance greater in the smaller airways or in the larger airways? Why?
It is greater in the larger airways because there are more air molecules within one tube
250
What impact does airway contraction have on airflow?
Increases it
251
How is the respiratory system able to alter airflow resistance?
Through the action of smooth muscle wrapped around bronchioles
252
What is the most significant determinant of airflow resistance?
The diameter of the airways
253
What does airway resistance determine?
How much air flows into the lungs at any given pressure difference between atmosphere and alveoli.
254
What surrounds an alveoli?
Elastic fibres and a capillary network
255
What is the function of the elastic fibres surrounding alveoli?
They facilitate the expansion of alveoli during inspiration
256
Name the two different cells making up an alveoli
Type 1 and type 2 pneumocystis
257
What is the function of type 1 pneumocytes?
Make up the alveoli and facilitate gas exchange
258
What is the function of type 2 pneumocytes?
produce surfactant
259
What is the third cell type you will find in an alveoli?
Aveolar macrophages
260
Is the surface area of an alveoli large or small?
Large!
