Respiratory physiology Flashcards
(91 cards)
1
Q
What are the average volumes of gas exchanged per minute?
A
Oxygen - 2050ml
Carbon dioxide - 200ml
2
Q
What is the standard resp rate at rest, and maximum when exercising?
A
10-20 at rest
40-45 during exercise
3
Q
What constitutes the URT?
A
Nasal cavity
Oral cavity
Pharynx
Larynx
4
Q
What constitutes the LRT?
A
Trachea
Bronhi
Lungs
5
Q
How is the patency of airways maintained?
A
C-shaped rings of cartilage in trachea/bronchi
In bronchioles maintained by physical forces
6
Q
What is the function of type 1 alveolar cells?
A
Gas exchange
7
Q
What is the function of type 2 alveolar cells?
A
Produce surfactant
8
Q
What is anatomical dead space?
A
Space in upper airways too thick to allow for gas exchange
9
Q
How is the respiratory tract lined?
A
With Pseudo-stratified ciliated columnar epithelium
Mucous membranes
10
Q
How does the lining change as you go down the respiratory tract?
A
Epithelium becomes more squamous
Mucous cells lost first
Cilia then lost
11
Q
What are the funtions of mucus?
A
Moistens air
Traps particles
Provides large surface area for cilia to act on
12
Q
What is boyles law?
A
Increase in volume means decrease in pressure and vice versa
Gasses always move from high to low pressure
13
Q
What muscles does inspiration use?
A
External intercostals
Diaphragm
Accessory:
SCM
Scalenes
14
Q
What muscles are used in expiration?
A
Passive at rest, but in load
Internal intercostal
Abdominal muscles
15
Q
What is intra-thoracic pressure?
A
Pressur einside thoracic cavity
Negative or positive compared to atmosphere
16
Q
What is intrapleural pressure?
A
Pressure inside pleural cavity
Always negative
17
Q
What is transpulmonary pressure?
A
Difference between alveolar pressure (intrathoracic) and intrapleural pressure Always positive (as Pip is always negative)
18
Q
What is tidal volume?
A
Volume of breath breathed in/out of lungs in each breath
TV
19
Q
What is expiratory reserve volume? ERV
A
Maximum volume of air which can be expelled from the lungs at the end of a normal expiration.
20
Q
What is Inspiratory reserve volume? IRV
A
Maximum volume of air which can be drawn into the lungs at the end of a normal inspiration.
21
Q
What is residual volume?
A
The volume of gas in the lungs at the end of a maximal expiration.
22
Q
What is vital capacity?
A
Tidal volume + inspiratory reserve volume + expiratory reserve volume
23
Q
What is total lung capacity?
A
Vital capacity + residual volume
24
Q
What is inspiratory capacity?
A
Tidal volume + inspiratory reserve volume
25
What is Functional residual capacity?
expiratory reserve volume + residual volume.
26
What is FEV1?
Forced expiration in 1 second
27
What is FEV1:FVC?
Fraction of Forced Vital Capacity expired in 1 second.
28
What is pulmonary ventilation?
total air movement into/out of lungs
29
What is alveolar ventilation?
fresh air getting to alveoli and therefore available for gas exchange
30
What is partial pressure?
Pressure of a gas in a mixture of gases is equivilent to percentage of that gas multiplied by pressure of all gas in mixture
31
What is the purpose of surfactant?
Increases lung compliance
Reduces surfaces tension of alveolar surface membrane
Reduces lungs tendancy to recoil
In effect makes breathing easier
More effective on smaller alveoli
32
When is surfactant produced in gestation?
Begins at 25 weeks
| Complete by 36 weeks
33
What is lung compliance?
Change in volume relative to change in pressure
| I.e stretchability of lung
34
What is emphysema?
Loss of elastic tissue resulting in greater effort of expiration
35
What is fibrosis?
Inert fibrous tissue that increases the effort of inspiration
36
Is the volume change greater at the apex of base of the lung?
At the base
37
Which area of the lung has higher compliance, the base or apex?
Base
38
What are the main obstructive lung diseases?
Asthma
| COPD
39
What are the main diseases that make up COPD?
Chronic bronchitis
| Emphysema
40
Through what mechanism do obstructive lung diseases make breathing harder?
Through increasing airway resistance
41
Through what mechanism do restrictive lung diseases make breathing harder?
Through loss of compliance
42
What are the normal values for FEV1/FVC in a health male?
```
FEV1 = 4L
FVC = 5L
FEV1/FVC = 80%
```
43
How does spirometry change in obstructive lung disease?
Rate of air expulsion is reduced
Total expired volume also reduced
Ratio reduced as FEV reduced more than FVC
44
How does spirometry change in restrictive lung disease?
Absolute flow of air reduced
Total volume reduced due to restriction on lung expansion
Ratio constant or can increase as large proportion of air can still be exhaled in first second
45
What is the pressure of arterial PO2?
100mgHg
| 13.3 kPa
46
What is the value of arterial Co2
40mgHG
| 5.3kPa
47
What is the rate of diffusion proportional to?
Directly to partial pressure gradient
Directly to gas solubility
Directly to available surface area
Inversely to thickness of membrane
48
How is gas echange effected by emphysema?
Due to destruction of alveoli there is reduced surface for gas exchange
Thus Po2 in blood is low
49
How is gas echange effected by fibrotic lung disease?
Thickened alveolar membrane slows gas exchange
Loss of lung compliance may reduce alveolar ventilation
Results in low PO2
50
How is gas echange effected by pulmonary oedema?
Fluid in intersitial space increases diffusion distance
Results in low PO2
However, due to CO2 being more soluble PCO2 may be normal
51
How is gas echange effected by asthma?
Increased airway resistance decreses ventilation
| PCO2 is decreased
52
What is the difference between ventilation and perfusion?
Ventilation is air getting to alveoli
| Perfusion is local blood flow
53
What two pressures determine blood supply to the lungs?
Arterial pressure
| Alveolar pressure
54
Is blood flow higher at base of lungs or apex, why?
Higher at base, because arterial pressure exceeds alveolar pressure causing vascular resistance to be low
At apex the arterial pressure is lower, and are therefore compressed increaseing resistance
55
How does the body respond to mismatched ventilation and perfusion?
Blood vessels that are not getting adequately perfused are constricted, which diverts the blood to vessels that have a higher oxygen content
56
What is alveolar dead space?
Alveoli that are ventilated but not perfused
57
What is pulmonary arterial pressure?
systolic 25mmHg
| Diastolic 8mmHg
58
What is the oxygen demand of resting tissues?
250ml/min
59
How many molecules of oxygen does each haemoglobin transport?
4 molecules
60
What is the main determinant of how saturated haemoglobin is with oxygen?
Partial pressure of oxygen in arterial pressure
61
How does the foetal haemoglobin + myoglobin curve differ from adult?
Both have a higher dissociation curve
| Means that they have a higher affinity resulting in more being bound to them
62
What is anaemia?
Any condition where the oxygen carrying capacity of the blood is comprimised
63
How does haemoglobin's oxygen affinity change with pH?
Higher affinity in alkalosis
| Lower in acidosis
64
What happens to the affinity to haemoglobin during exercise (hint: lactic acid)
It would lower, allowing for more oxygen uptake by muscles
65
How does haemoglobin's oxygen affinity change with temp?
Higher affinity at lower temperatures
| Lower affinity at higher temperatures
66
How does haemoglobin's oxygen affinity change with PCO2?
Higher affinity with lower PCO2
| Lower affinity with high PCO2
67
What factors affect haemoglobin's affinity curve?
pH (proportionatly)
PCO2 (inversely)
Temperature (inversely)
2,3-DPG (inversely)
68
What is 2,3-DPG?
2,3-diphosphoglycerate
Synthesised by erythrocytes in response to inadequate oxygen supply
Helps maintain oxygen release at tissues
69
What are the types of hypoxia?
```
Hypoxic
Anaemic
Ischaemic
Histotoxic
Metabolic
```
70
What is hypoxic hypoxia?
Most common
| Reduction in oxygen diffusion at lungs
71
What is anaemic hypoxia?
Reduction in oxygen carrying capacity due to anaemia
72
What is ischaemic hypoxia?
Heart disease resulting in inefficient pumping of blood to lungs/body
73
What is histotoxic hypoxia?
Poisoning of cells preventing utilisation of delivered oxygen
74
What is metabolic hypoxia?
Oxygen delivery not meeting increased oxygen demand of tissues
75
Why does hypoventilation cause respiratory acidosis?
Due to CO2 retention
| The equilibrium means that more bicarbonate is produced as well as H+
76
What is the action of carbonic anhydrase in CO2 transport?
Catalyses reaction of CO2 + water to form carbonic acid
77
How is CO2 carried in the blood?
7% in plasma and erythrocytes,
23% combines with deoxyhaemoglobin to form carbamino compound,
70% form carbonic acid with water again in erythrocytes.
78
Why does hyperventilation cause respiratory acidosis?
Less CO2 so equilibrium shifts, results in decreased H+
79
What happens to the carbonic acid produced in the red blood cells?
It splits into Hydrogen and bicarbonate ions
Bicarbonate exchanged for chloride ions
Hydrogen ions binds with deoxyhaemoglobin
80
By what nerves is ventilation controlled?
Phrenic
| Intercostal
81
What modulates the rhythm of respiratory centres?
Emotion (via limbic system)
Voluntary over-ride
Mechano-sensory input from thorax
Chemical composition of blood due to chemoreceptors (most significant)
82
What are the central chemoreceptors, what do they respond to?
Medulla
Directly to H+ in CSF around brain (reflects PCO2)
acts as primary ventilation drive
83
What are the peripheral chemoreceptors, what do they respond to?
Carotid and aortic bodies
Respond to plasma [H+] and PO2
Acts as secondary ventilatory drive
84
What happpens to ventilation in a decrease of CSF {H+}?
Decreased breathing = hyperventilation
85
How do central chemoreceptors detect a raised PCO2 level in the blood?
Raised PCO2 leads to diffusion across blood brain barrier
Dissociates into bicarbonate and H+
H+ detected by chemoreceptor
Increases ventilation rate, leading to decreased PCO2
86
How do peripheral chemoreceptors respond to a change in PO2?
Ventilation occurs after a significant fall in PO2 (NOT oxygen content)
87
How does ventilation change with vomiting?
Vomiting causes alkalosis
Therefore as pH increases, ventilation in inhibited
CO2 then retained due to hypoventilation
88
How does hyperventilation cause alkalosis?
Increased ventilation means that more CO2 is being cleared
This results in [H+] lowering
Results in alkalosis
89
How does hypoventilation cause acidosis?
Decreased ventilation means less CO2 is being cleared,
Results in [H+] rising
Results in acidosis
90
What are the limitations of voluntary control of breathing?
Cannot override involuntary stimul such as PCO2 or [H+]
91
How is the airway protected during eating?
Respiration inhibited during swallowing to avoid aspiration
| Swallowing followed by expiration in order to dislodged particles around glottis outwards.
