Lungs Flashcards
0
Q
What is pressure?
A
P = F / A Pressure Force Area Unit is Pa
1
Q
What is Boyles law? And how does it influence gas exchange?
A
Absolute pressure exerted by gas is inversely proportional to volume it occupies if temp and amount of gas remain unchanged in closed system
P1V1 = P2V2
Creates the pump and vacuum activity in lungs that allows us to breathe
2
Q
What is Charles’ law?
A
At constant pressure, the volume of gas changes in direct proportion to its temperature on the absolute temperature scale
V = KT (K is a constant)
V1/T1=V2/T2
3
Q
What is the universal gas law?
A
PV = nRT P is pressure V is volume n is number of moles of gas R is gas constant T is temperature Allows calculation of volume changes with pressure and temperature changes
4
Q
What is a partial pressure?
A
When two gases in a mixture do not interact, they behave independently and each exerts its own pressure
5
Q
What is Dalton’s law?
A
In a mixture of non reacting gases, total pressure exerted is equal to sum of partial pressures
6
Q
What is the partial pressure of O2 in air?
A
21.1 kPa
7
Q
What factor is saturated vapour pressure dependent on?
A
Temperature
Increased kinetic energy allows more vapour to escape the surface of the liquid
9
Q
What is Henry’s law?
A
Number of molecules of gas dissolving in solvent is directly
proportional to the pressure of the gas at the surface of the
liquid
10
Q
What happens to tension of a gas dissolving in water at equilibrium?
A
Tension proportional to partial pressure of that gas in adjacent gas mixture
11
Q
What does gas tension indicate?
A
How readily a gas will leave a liquid
12
Q
What is gas tension measured as?
A
Partial pressure of solute in solvent in kPa
13
Q
What is the content of a gas in a liquid?
A
Proportional to its solubility in that liquid and the gas tension at
equilibrium
14
Q
What is saturated vapour pressure at 37 degrees?
A
6.28 kPa
15
Q
What is a difference between convection and diffusion?
A
No net transport of matter in diffusion
16
Q
How much oxygen is picked up by the blood in health?
A
12 mmol O2 per minute
17
Q
What is an alveolus?
A
Thin spherical structure where gas exchange occurs
Surrounded by capillary plexus
Fed through tiny bronchiole called alveolar duct
18
Q
What constitutes total content of gas in a liquid?
A
Total reacted gas and gas dissolved in liquid
19
Q
In blood, final gas content is determined by…
A
Gas tension
Solubility of gas in liquid
Avidity of haemoglobin for oxygen
20
Q
Where does gas exchange occur?
A
At alveolar membrane
21
Q
How does the composition of alveolar gas differ from atmospheric?
A
Lower pO2 - 13.3 in alveolar, 21.1 kPa in atmosphere
Higher pCO2 - 5.3 in alveolar, minimal in atmosphere
22
Q
How does mixed venous blood gas composition vary from alveolar?
A
pO2 - 6 kPa venous, 13.3 alveolar
pCO2 - 6.5 kPa venous, 5.3 alveolar
23
Q
What factors affect diffusion rate?
A
Surface area of alveoli
Concentration gradient caused by differences in partial pressures
Resistance of alveolar capillary membrane - thickness
Solubility of gas
Molecular weight of gas
Diffusion rate = D x A x (difference in PP/thickness)
D is proportional to solubility / root of MW
24
Q
What constitutes the diffusion barrier of the alveolar membrane?
A
Diffusion through gas to alveolar wall Epithelium of alveolus Tissue fluid and connective tissue Endothelium of capillary Plasma Red cell membrane Cytoplasm
25
What is solubility?
Amount of solvent that can dissolve in unit volume of solute
26
Which diffuses faster, O2 or CO2?
CO2
27
Is oxygen transfer perfusion or diffusion limited?
Perfusion
28
What may cause a change from perfusion limited oxygen delivery to diffusion limited?
Thickening of diffusion barrier - alveolar membrane
29
Other than gas exchange, what functions does the respiratory system have?
Reservoir for blood and oxygen
Metabolism of circulating compounds eg ACE
Filter blood
30
Which part of the airways form the anatomical dead space?
Conducting airways - bronchi and bronchioles
31
Which parts of the airways form the respiratory airway?
Respiratory bronchioles
Alveolar ducts
Alveolar sacs
32
What name is given to each level of branching of the bronchial tree?
Generation
33
What is hypoxic vasoconstriction?
In alveoli with low pO2 due to lower ventilation levels, pulmonary arterioles can be constricted to reduce blood flow to this area where it is not needed
34
Give an example of a disease which increases the thickness of the diffusion barrier
Pulmonary fibrosis
35
Give an example of a disease which reduces the surface area available for diffusion
COPD - chronic obstructive pulmonary disease
36
What non disease state can cause a switch from perfusion to diffusion limited oxygen delivery?
High levels of exercise as the perfusion rate is so fast that the diffusion rate cannot keep up
37
What can be used as lung function test to determine the thickness of the alveolar membrane?
Carbon monoxide as its delivery is diffusion limited
38
How can rate of gas exchange be increased when a gases delivery is diffusion limited?
Increase pO2 in alveoli
39
Which muscles are involved in ventilation?
Diaphragm
| Intercostal muscles
40
What do you use spirometry for?
Measure lung volumes
41
What 4 parts make up total lung capacity?
Tidal volume
Residual volume
Inspiration reserve volume
Expiratory reserve volume
Maximum force generated by inspiratory muscles balanced by opposing forces
42
In spirometry, what is the difference between lung volumes and lung capacities?
Lung volumes change with breathing pattern
| Lung capacities do not
43
What factors determine an individual's lung capacities?
Properties of lung, chest wall and muscles
44
Which lung volumes make up inspiratory capacity?
Tidal volume and inspiratory reserve volume
Biggest breath that can be taken from resting expiratory level (lung
volume at end of quiet expiration) Inspiratory capacity typically ~3l
45
Which lung volumes form the vital capacity?
Tidal volume
Inspiratory reserve volume
Expiratory reserve volume
Biggest breath that can be taken, often changes in disease
46
Which lung volumes make up the functional residual capacity?
Residual volume
Expiratory reserve volume
Volume of air in the lungs at resting expiratory level
Typically ~2 litres Determined by the balance of elastic resistance
between lung and chest wall
47
What is a normal value for vital capacity?
5L
48
What is minute ventilation (MV)?
Amount of air moved into and out of the lungs or minute
Product of tidal volume and respiratory rate
MV=Vt x RR
Typically 6-8 L/min at rest
49
What must be calculated to work out the alveolar ventilation rate?
Amount of wasted ventilation into dead space
50
What volume of inspired air is within the serial dead space and therefore doesn't take part in gas exchange?
150 ml
51
What is the distributive dead space?
Dead or damaged alveoli
| Alveoli with poor perfusion
52
What is the physiological dead space?
Serial and distributive dead spaces combined
53
What type of breathing amplifies dead space effect?
Rapid and shallow
54
What is the ideal V/Q ratio?
1
55
What is the main reason for defective gas exchange in disease?
V/Q mismatch
56
What would total lung V/Q mismatch cause?
Arterial hypoxaemia
57
Give an example of a disease which causes a decrease in ventilation and therefore gives a lower V/Q ratio?
Pneumonia
58
Give an example of a disease which causes decreased perfusion and therefore increases the V/Q ratio
Pulmonary embolus
59
Describe the V/Q ratio in the apex of the lung and how this differs to the base
In the apex, the ventilation rate is greater than the perfusion so the V/Q ratio is above 1
In the base, perfusion (gravity dependent) is greater than ventilation rate and so the V/Q ratio is below 1
60
Why is perfusion of the central part of the lung sporadic?
Systole and diastole of the heart mean that pressure changes
61
What causes the reduction in pH as you move down from apex to base of lungs?
Increasing CO2 levels in alveoli and capillaries. CO2 transfer is ventilation dependent
62
Why is apical alveolar pO2 relatively high?
Less perfusion
| O2 transfer is perfusion dependent
63
What happens in the lung during exercise to accommodate increased CO?
Distensible apical blood vessels that are usually collapsed, open. This increases oxygen uptake at the top of the lung
64
What 5 things can cause hypoxia?
```
Shunt
V/Q mismatch
Limited diffusion
Hypoventilation
Decreased O2 in inspired air
```
65
Which pathological cause of hypoxia cannot be corrected with increasing inspired oxygen?
Pulmonary shunt
66
What factors does oxygen delivery to tissues rely on?
```
Cardiac output
Haemoglobin concentration
Oxygen saturation
Dissolved oxygen
DO2 = CO x (( Sa02 x Hb x k) x ( PaO2 x 0.023 ))
```
67
Which ribs end in costal cartilage?
1-10
68
What is flail chest?
When a segment of thoracic cage is separated from rest of chest wall. At least 2 fractures per rib which produces a free segment. This segment is unable to contribute to lung expansion, paradoxical movement
69
What can be a consequence of having an additional cervical rib?
Thoracic outlet syndrome
Brachial plexus gets squashed
Muscle wasting in the hand
70
What 3 parts make up the sternum?
Manubrium
Body
Xiphoid process
71
At what thoracic level would you find the sternal notch?
T2
72
What do you find at the sternal angle?
T4
| 2nd rib
73
What level do you find the xiphoid process at?
T9/10
74
Which part of the ribs forms a joint with the vertebrae?
Articular facets of head
75
Which ribs connect directly to the sternum?
Ribs 1-7
76
Which ribs connect to the sternum via the costal cartilage of the ribs above?
Ribs 8-10
77
What are the 3 layers of intercostal muscle?
External intercostal
Internal intercostal
Innermost intercostal
78
Where would you make an incision in the intercostal space?
Just above the rib to avoid the neurovascular bundle at the top of the space
79
What does an intercostal nerve supply?
```
Skin
Muscle
Bone
Cartilage
Parietal pleura
```
80
Where can pleuritic pain and shingles refer to?
Dermatome of the spinal nerve of origin
81
Where does the sympathetic chain lie in the thoracic cavity?
Posterior thoracic wall
82
What can a pancoast tumour cause?
Compression of the sympathetic chain in the apical region of the lung
Can cause Horner syndrome due to compression of the T1 spinal nerve
83
Which artery can be harvested for coronary artery bypass graft?
Internal thoracic artery
84
Where does the blood supply to the thoracic wall derive from?
Intercostal arteries which form anastomotic loops
85
Where do posterior intercostal arteries branch from?
Descending aorta
86
Where do anterior intercostal arteries branch from?
Internal thoracic artery
| Musculophrenic artery
87
Where does the internal thoracic artery branch from?
Subclavian artery
88
What is the venous drainage of the thoracic wall?
Azygous venous system
Azygous vein on right
Hemiazygous on left
89
What does the azygous vein drain into?
Superior vena cava
90
What can damage of the thoracic duct lead to?
Chylothorax
91
Which areas of mediastinum does thoracic duct run through?
Posterior
| Superior
92
Where does the thoracic duct start and finish?
Starts at cisterna chyli
| Ends at left subclavian vein
93
Where does the diaphragm attach?
Costal margin
Ribs 10-12
Lumbar vertebrae
94
Name 2 types of congenital diaphragmatic hernia
Bochdalek hernia - posterior left sided
| Morgagni hernia - retro sternal
95
Which nerve innervates the diaphragm?
Phrenic nerve C3-5
96
What can unilateral damage to the phrenic nerve cause?
Hemidiaphragmatic palsy
97
Which 3 structures pierce the diaphragm and at what levels?
Inferior vena cava T8
Oesophagus T10
Descending aorta T12
98
At what time during development does the respiratory diverticulum form as an outpouching of the gut tube?
4 weeks
99
What developmental tissue type are the lining of lungs and glands derived from?
Endoderm
100
What developmental tissue type are the blood vessels, cartilage, smooth muscle and visceral pleura derived from?
Mesoderm
101
During development, what divides the oesophagus and trachea?
Tracheo-oesophageal septum which forms weeks 4-5
102
What 2 developmental defects can occur if septation of the trachea and oesophagus fail?
Blind ended oesophagus
| Fistula
103
How many bronchial buds form?
3 on right, 2 on left
104
At what time during development do segmental bronchi form?
Week 7
105
What part of respiratory development occurs at week 26? And what consequence can this have for premature babies?
Initial development of respiratory epithelia
| Premature babies lungs are not fully developed and so survival rates are lower
106
What does the horizontal fissure divide?
Right middle and superior lobes
107
Which structures are closely related to the right lung?
Oesophagus
Azygous vein
Brachiocephalic vein
SVC and IVC
108
Which structures are closely related to the left lung?
```
Aortic arch
Descending aorta
Cardiac impression
Subclavian artery
Brachiocephalic vein
```
109
Where does the phrenic nerve pass in relation to the hilum of the lung?
Anterior
110
Which structures pass through the hilum of the lung?
Main bronchi
Pulmonary artery
Autonomic nerves
Pulmonary vein
111
What is the pulmonary ligament?
Fold of parietal pleura at hilum
112
What occurs if a venous thrombus passes into the lungs via pulmonary artery?
Pulmonary embolism
113
What does the parietal pleura line?
Thoracic cage (costal)
Mediastinum
Cervical region
Diaphragm
114
What holds together the pleural layers at rest?
Surface tension
115
What signs will you see with a tension pneumothorax?
```
Mediastinal shift away from pneumothorax
Tracheal deviation
Diaphragmatic depression
Unilateral hyperinflation
Increased intercostal space size
Hyper resonant
```
116
At what point does the trachea bifurcate?
T4 - sternal angle
117
What vertebral level is the horizontal fissure located at?
4th costal cartilage, horizontally to join the oblique fissure
118
Where does the oblique fissure start and finish?
T3 spinous process posteriorly
| 6th costal cartilage anteriorly
119
Which spinous process is the most prominent in the neck?
C7
120
Biopsy of which structures will require crossing through the costodiaphragmatic recess?
Liver, spleen, kidneys
121
Where are chest tubes classically inserted?
Triangle of safety
| Bordered by posterior, anterior axillary lines and nipple line (4-5th intercostal space)
122
Where does the trachea start?
Cricoid cartilage in larynx C6/7
123
What are the walls of the trachea supported by?
Hyaline cartilage
124
What happens to carina if the lymph nodes below it are enlarged? (Tracheobronchial nodes)
Become more rounded in shape
125
Which bronchus is more likely to get aspirated food entering it and why?
Right main bronchus because it is more vertical
126
Where do pulmonary arteries and veins run in relation to pulmonary segments?
Pulmonary arteries run with bronchi and bronchioles
| Pulmonary veins run between segments
127
How many segments does each lung have?
Right - 10
| Left - 9
128
What is atelactasis?
Collapse or closure of lung
129
Which segment is least well drained in the supine position and so a likely site for hospital acquired pneumonia?
Superior bronchopulmonary segment of inferior lobe because it's bronchus has to drain against gravity in this position
130
Where does the left upper lobe drain to?
Bronchomediastinal duct -->thoracic duct and left subclavian vein
131
Where does lung lymph drainage go to (apart from the left upper lobe)?
Bronchomediastinal duct --> right lymphatic duct to right subclavian vein
132
When does acute respiratory failure occur?
When pulmonary system is unable to meet metabolic demands of the body
133
What is hypoxaemic respiratory failure?
PaO2 < or equal to 8kPa when breathing room air
| Type 1
134
What is hypercapnic respiratory failure?
PaCO2 > or equal to 6.7kPa
| Type 2
135
What is the alveolar gas equation?
```
PAO2 = (FiO2 x (P atmos - P H2O)) - (PaCO2 / RQ)
FiO2 - fraction of inspired oxygen
P atmos - atmospheric pressure
P H2O - water vapour pressure
RQ - respiratory quotient (0.8)
```
136
What are the levels of expired CO2 largely dependent on?
Alveolar ventilation
137
How can alveolar ventilation be calculated?
Alveolar ventilation = respiratory rate x (tidal volume - dead space)
138
Which dead space is constant? And which can vary and why?
Anatomical dead space constant
| Physiological dead space can vary depending on ventilation perfusion matching
139
What mechanism tries to maintain ventilation perfusion matching?
Hypoxaemic pulmonary vasoconstriction
140
In what circumstances will supplemental oxygen not be beneficial?
Absolute shunt where ventilation is blocked
| When someone has chronically high levels of CO2 and therefore hypoxaemia is driving their breathing
141
What factors could cause hypoxaemia?
Low levels of inspired O2
Hypo ventilation
V/Q mismatch - shunt
Diffusion abnormality
142
At what sites may disease cause hypo ventilation?
```
Brainstem - head injury, drug overdose
Spinal cord - sci c3-5
Spinal nerve root - guillain barré syndrome
Nerve - demyelination
Neuromuscular junction - myesthenia gravis
Respiratory muscle - muscular dystrophy
Chest wall
Pleura
Lung
Airway
```
143
What can cause shunts in the lung?
```
Pneumonia
Pulmonary oedema
Atelactasis
Collapse
Pulmonary haemorrhage or contusion
Right to left shunt of heart - congenital heart disease, pulmonary hypertension
```
144
What can be a cause of diffusion abnormality?
PCP - pneumocystis pneumonia in immunosuppressed patients
Acute respiratory distress syndrome - widespread inflammation
Alveolitis
145
What is a hallmark sign of diffusion abnormality?
Desaturation on exercise
146
What is a normal venous oxygen saturation?
| And what happens to this value if you half cardiac output?
Normal value 75%
| Reduced to 50% if CO is halved
147
What are signs of respiratory compensation?
Tachypnoea
Use of accessory muscles
Nasal flaring
Recession (gaps between ribs get sucked in)
148
What can tissue hypoxia result in?
Altered mental state
Lactic acidosis
Decrease HR and decrease BP (late)
149
What can be sources of error in using pulse oximetry to measure sats?
```
Poor peripheral perfusion
Poorly adherent or positioned probe
False nails or nail varnish
Lipaemia
Bright ambient light
Excessive motion
Carboxyhaemaglobin or methaemoglobin
```
150
What can hypercapnia result in?
Sympathetic stimulation
Respiratory acidosis
Flapping tremor
If severe (>10 kPa) unconsciousness and respiratory depression
151
What are signs and symptoms of severe respiratory failure?
```
RR > 30 /min or < 8 /min
Difficulty completing sentences
Agitated, confused or comatose
Cyanosed
SpO2 <90%
Deterioration despite therapy
```
152
What are treatment options with respiratory failure?
Oxygen therapy
CPAP - continuous positive airway pressure to open collapsed alveoli
Mechanical ventilation
153
What could you do to help with pneumonia?
Antibiotics
| Physiotherapy
154
What can be done to help with pulmonary oedema?
Vasodilators
| Diuretics
155
What can you do to help with a pneumothorax?
Chest drain
156
What can be given in an opiate overdose?
Naloxone
157
What are the 2 types of oxygen delivery devices?
Fixed and variable performance devices
158
What is a disadvantage of mechanical ventilation?
Requires sedation and an endotracheal tube
159
What factors affect the decision to ventilate or not?
```
Severity of respiratory failure
Cardiopulmonary reserve
Adequacy of compensation
Expected speed of response -underlying disease, treatment
Risks
```
160
What are the risks of mechanical ventilation?
Secondary infection
Pneumothorax
Ventilator induced lung injury
Risks from immobility - venous thromboembolism, pressure ulceration
161
What is PEEP?
Positive end expiratory pressure
Alveolar pressure above atmospheric pressure that exists at end of expiration. Can be applied in ventilated patients to prevent collapse of alveoli at end of expiration
162
What is lung volume determined by?
Elasticity of lungs
| Properties of chest wall
163
What is compliance?
Measure of stiffness of the lung
164
What lung volume is represented when the forces inflating and deflating the lungs are equal?
Forced residual capacity
165
The lungs are not adherent to the inside of the thoracic cavity. What stops themfrom collapsing away from the chest wall?
Negative pressure in chest that keeps lungs inflated
166
Where are alveoli the biggest and why?
Higher negative pressure at top of lungs
167
Which parts of the lung move the most during inspiration?
Bigger volume change at bottom of lungs due to the way the ribs move
168
What effects do the shape of the ribs have on the way they move?
Upper ribs move like pump handle
| Lower ribs move like bucket handle so allow for greater expansion
169
Which muscles are used during inspiration?
Scalenes - fix thorax
External intercostals - posterior
Internal intercostals - anterior
Diaphragm
170
Which muscles are used in active expiration?
Abdominal muscles
Intercostals
Pectoral girdle muscles
171
Explain how the respiratory pattern of a patient with a low cervical spinal injurydiffers from a patient with a low thoracic spinal injury?
Cervical SCI - loss of use of intercostal muscles and accessory muscles so see saw breathing where diaphragm is pulled down but chest cannot expand sufficiently. Abdomen distends and chest caves in.
Thoracic SCI - all muscles of breathing will be able to function so normal breathing
172
How do you measure compliance?
Change in volume / change in pressure
173
What is specific compliance?
Relates compliance to actual volume
Volume change per unit pressure change / starting volume of lung
Babies lungs, not stiffer but compliance would give incorrect value, specific compliance gives more accurate measure
174
What is hysteresis?
Difference in lung compliance due to additional energy required during inspiration to recruit and inflate additional alveoli
175
What is LaPlace's law?
Larger vessel radius, larger wall tension required to withstand a given internal fluid pressure. For a given vessel radius and internal pressure, a spherical vessel will have half the wall tension of a cylindrical vessel
For an alveolus - P=2T/r
176
What is surface tension?
At a surface: attractive forces between molecules of a liquid are much stronger than those between liquid and gas. Surface becomes as small as possible. Measured as force required to change surface area per unit length
177
What does surfactant do?
Lines the alveoli and reduces surface tension which prevents small alveoli emptying into large
178
Which cells secrete surfactant?
Type II cells lining alveoli
179
What is surfactant?
```
Mixture of phospholipid compounds, principally dipalmitoyl phosphatidylcholine
Hydrophobic, projects into the gas phase of the alveolus
Surfactant proteins (SP-A, B, C, D)
```
180
What can lead to a depletion of surfactant?
Lack of blood supply
181
What effects does surfactant have?
Reduces work of breathing by reduction in surface tension and increasing compliance
Reduces the likelihood of tissue fluid transudation
The lipid component of surfactant has an antioxidant activity
SP-A and D can bind a wide range of pathogens
SP-A and D can activate macrophages and neutrophils via specific receptors
182
When are the airways narrowest?
During expiration as positive intrathoracic pressure decreases diameter
183
Where in the lungs does turbulent flow occur?
Trachea
184
Where in the lungs does laminar flow occur?
Terminal bronchioles
185
What factors affect compliance?
Lung volume
Diameter of alveoli
Content of alveoli
Integrity of surfactant production
186
What factor of hysteresis allows V/Q matching?
Alveoli at bottom of lung are smallest, but are on most compliant part of hysteresis curve and so when pressure is increased, they can expand more to match perfusion
187
Which category of lung defect will result in an almost normal FVC but a largely reduced FEV1?
Obstructive defect eg COPD
188
Which category of lung defect will result in a reduced FEV1 and a largely reduced FVC?
Restrictive defect eg pulmonary fibrosis
189
Where does automatic control of breathing originate?
Dorsal respiratory group - inspiration
Ventral respiratory group - expiration and inspiration
Sensory nerves IX and X send chemoreceptor, baroreceptor and stretch receptor signals to dorsal respiratory group
190
Where does the ventral respiratory group signal to?
Accessory muscles in active respiration via u opioid receptors
191
What does the pneumotaxic centre do?
Switch of inspiratory ramp
| Control respiratory rate
192
What is the Hering Breuer reflex?
```
Stretch receptors in airways
Signal travels via vagus nerve afferents
Respiratory centre in medulla
Inhibits inspiratory neurones
Inspiration is ended, allowing expiration
```
193
Where are peripheral chemoreceptors located?
Carotid bodies
| Aortic arch
194
Via what nerve do the peripheral chemoreceptors in the carotid bodies signal to the medulla?
CN IX
195
Where are central chemoreceptors located and what do they detect?
2mm below ventral surface of medulla
| Detect pH of CSF
196
What can prolonged vomiting cause in terms of acid base balance?
Metabolic alkalosis
197
A 24yr old woman is hyperventilating. If she continues what will the physiological consequences be and why does she appear to have a ‘cardiac arrest’ before making a spontaneous recovery?
Low CO2. Becomes alkalotic. Calcium levels go up so nerves and muscles become more active - spasm
Brains response tells respiratory system to slow down but higher systems are overriding signal. Eventually response becomes overwhelming and cant override it, so she stops breathing. CO2 level rises. Paper bag works because she rebreathes expired gas and increases CO2
198
A 76 yr old man is given morphine for post operative pain relief following an elective abdominal aortic aneurysm repair. Explain the physiological consequences that may occur in this situation
Breathing decreased so CO2 levels increase. So tachycardic, sweating etc due to sympathetic stimulation. Continued CO2 increase - respiratory depression so can become comatosed - overdose
Supplemental morphine in hospital, given supplemental oxygen to compensate for modest hypoxia
199
Give 4 reasons for doing lung function tests
Provides aid to diagnosis
Can follow changes in lung function over time
Can assess those at risk of pulmonary disease and those with symptoms
Can assess changes in response to specific stimuli
200
What is air flow rate a good measure of?
Diameter of airways
201
What does measuring vital capacity tell us?
A measure of total lung volume
202
What is carbon monoxide used for as a lung function test?
Measures permeability of lung membranes
203
What 2 factors can the peak flow meter tell us about?
Diameter of bronchial tree
| Muscle power available to blow air out of lungs
204
What factors are important when taking a peak flow meter reading?
Pointer at zero to start
Stood or sat in comfortable position
Peak flow meter horizontal
Deep breath out, deep breath in then wrap lips tightly around mouthpiece
Blow as hard as possible using maximum force
Repeat 3 times and record highest value
205
What peak flow results would you expect to see from an asthmatics peak flow diary?
Diurnal variation with lower values in the morning
| >20% variability in readings over time in untreated or poorly controlled asthma
206
What information can be discerned from a flow volume loop?
Peak expiratory flow PEF
Forced vital capacity FVC
Forced expiratory volume in 1 second FEV1
207
What does a time volume loop show?
Forced vital capacity FVC
| Forced expiratory volume in 1 second FEV1
208
Which is the best index of lung restriction?
Reduced forced vital capacity
209
Which is the best index for measuring lung obstruction?
Reduced FEV1
210
Why will airway obstruction make the residual volume increase?
Air gets trapped at end expiration
211
What are normal FEV1 and FVC values?
Over 80% of predicted values
212
What happens to the ratio of Fev1/ FVC in obstructive airways?
Reduces below 0.7
213
What happens to the ratio of Fev1/ FVC in restrictive airway disease?
Increase above 0.7
214
What are contraindications to lung function tests?
Haemoptysis
Closed or recent (within 2 weeks) pneumothorax
Unstable CV status
Pre eclampsia
Hypertension (MAP above 130mmHg)
Thoracic, abdominal or cerebral aneurysms
Acute illness that may interfere with results
Recent thoracic, ear, eye or abdo surgery
Active communicable diseases eg TB
215
What is bronchitis?
Infection and inflammation of the airways
216
What are symptoms of bronchitis?
Dyspnoea
Cough
Wheeze
Sputum
217
What are signs of bronchitis?
Fever
Tachypnoea
Crackles
Wheeze
218
What would you see from investigations of a patient with bronchitis?
Hypoxia
| Normal chest X-ray
219
What is pneumonia?
Infection and inflammation of the alveoli
220
What are the symptoms of pneumonia?
Dyspnoea
Cough
Sputum
Pleurisy
221
What are signs of pneumonia?
Fever
Tachypnoea
Crackles
Decreased or bronchial breath sounds
222
What would you see from investigations of a patient with pneumonia?
Possible hypoxia
| Visible consolidation on chest X-ray
223
Why do you hear abnormal breath sounds in pneumonia patients?
Fluid filled area does not attenuate sound as much as air
| Pneumonia there are areas of pus in the alveoli
224
What types of infection generally cause acute and chronic bronchitis?
Acute - viral typically: rhinovirus, flu virus
| Chronic - bacterial: strep pneumoniae, Haemophilus influenzae
225
Which microbes typically cause pneumonia?
Influenza virus
Strep pneumoniae
Staph aureus
226
What respiratory condition does TB cause?
Bronchopneumonia with or without haemoptysis
227
What investigations might be ordered for a suspected lower respiratory tract infection?
```
PEF
FBC
U&Es
CRP
Lactate
ABGs
CXR
Nose and throat swabs
Sputum
```
228
What treatment can be provided for a lower respiratory tract infection?
```
Sepsis care package if sepsis
Oxygen if hypoxic
Antimicrobials
IV fluids if signs of AKI
Bronchodilators and steroids for bronchitis
Saline nebuliser for expectoration
Chest physio for expectoration
Ventilatory support if respiratory failure
```
229
What is CURB 65?
```
Confusion
Urea > 7mmol/L
RR > 30/min
BP < 90 mmHg systolic 60 mmHg diastolic
Age > 65
If score >1 admit, if >2 IV treatment
```
230
What antimicrobial would be used against influenza in acute bronchitis?
Oseltamivir
231
What antimicrobial would be used against H. Influenzae in chronic bronchitis?
Co amoxiclav
232
What antimicrobial(s) would be used against community acquired pneumonia?
Amoxicillin and Clarithromycin
233
What antimicrobial would be used against hospital acquired pneumonia?
Piperacillin-tazobactam
Piperacillin is antibiotic
Tazobactam is beta lactamase inhibitor
234
What antimicrobial should be used against staph aureus, particularly if there are concerns over MRSA?
Linezolid
235
What would you expect to see on a chest X-ray of a patient with COPD?
Hyper inflated thorax
Flattened diaphragm
Increased hilar shadow
Bullae (in emphysema)
236
What are symptoms of asthma?
Cough
Wheeze
SOB - worse at night
Chest tightness
237
What are causes and triggers of asthma?
```
Environmental allergen
Viral infection
Cold air
Emotion
Irritant vapours and fumes
Genetic factors
Drugs - NSAIDs, B blockers
Atmospheric pollution
Exercise
Occupational sensitisers
```
238
What are 3 key features of asthma?
Airway obstruction - reversible
Airway hyper responsiveness
Airway inflammation
239
What may be visible with histology of asthma airway?
Thickened basement membrane
Mucus plug with eosinophils and desquamated epithelial cells
Infiltration of mast cells, mononuclear cells, eosinophils in mucosa and submucosa
Oedema in mucosa and submucosa
Hypertrophied smooth muscle
Vasodilation
240
What events happen in the immediate/early phase of asthma pathogenesis?
Pre sensitised mast cells encounter allergen and release histamine and other mediators which cause bronchoconstriction
241
What events happen in the late phase of asthma pathogenesis?
Factors released from mast cells and T helper cells recruit other eosinophils and neutrophils
Cells infiltrate the mucosal layers, vascular leak occurs, mucus secretion increases
Mucus plugs cause a second wave of airway obstruction
242
What events happen in the chronic/remodelling phase of asthma pathogenesis?
```
Eosinophils cause damage due to repeated attacks
Smooth muscle hypertrophy
Smooth muscle and epithelial hyperplasia
Epithelial damage
Basement membrane thickening
```
243
Which drugs are used to treat the immediate phase of asthma?
B2 agonists
CysLT antagonists
Theophylline
244
What drugs are used to treat the late phase of asthma?
Glucocorticoids
245
What is type 1 brittle asthma?
Wide PEF variability
| >40% diurnal variation for 50% of time over >150 days despite therapy
246
What is type 2 brittle asthma?
Sudden severe attacks on background of well controlled asthma
247
What is acute severe asthma?
PEF 33-50% of best or predicted
Respiratory rate >25 / min
Heart rate > 110 / min
Inability to complete sentences in one breath
248
What are signs of life threatening asthma?
```
Altered consciousness
Exhaustion
Arrhythmia
Hypotension
Cyanosis
Silent chest
Poor respiratory effort
PEF <8kPa
```
249
What treatments can be used in acute asthma management?
Oxygen to maintain sats above 94%
B2 agonist nebuliser or MDI (metered dose inhaler) via spacer, repeat at 15-30 min intervals
Glucocorticoids to reduce late phase - prednisolone 40-50mg, hydrocortisone 100mg QDS (4x day) IV, continue for 5 days
Ipratropium bromide or magnesium sulphate if poor response to bronchodilators
Antibiotics where infection present
250
What is COPD?
Umbrella term for chronic irreversible obstructive airway disease
251
What are the clinical features of COPD?
Productive cough
Wheeze
Dyspnoea
Frequent infective exacerbations with purulent sputum
Cyanosis and oedema - blue bloater - insensitive to CO2 or
Tachypnoeic and pink - pink puffer - responsive to CO2
Signs of respiratory failure
252
Describe COPD pathophysiology
Alveolar macrophages and damaged epithelial cells stimulate release of cytotoxic T cells and neutrophils
This causes airway inflammation, remodelling, parenchymal destruction, loss of alveolar attachments and decrease of elastic recoil
253
What are the reversible causes of airway obstruction in COPD?
Accumulation of inflammatory cells, mucus and plasma exudate in bronchi
Smooth muscle contraction
Dynamic hyperinflation during exercise
254
What are the irreversible causes of airway obstruction in COPD?
Fibrosis and narrowing of airways
Loss of elastic recoil due to alveolar destruction
Destruction of alveolar support that maintains latency of small airways
255
Describe pathophysiology in large airways in COPD
```
Mucus hyper secretion
Goblet cell hyperplasia
Mucus gland hyperplasia
Increased cytotoxic T cell and macrophage infiltration
Squamous metaplasia of epithelium
Neutrophils in sputum
```
256
Describe pathophysiology in small airways in COPD
```
Inflammatory exudate in lumen
Disrupted alveolar attachments
Thickened wall with cytotoxic T cells, macrophages and fibroblasts
Peribronchial fibrosis
Lymphoid follicle
Destruction of pulmonary capillary bed
Loss of elasticity
```
257
What can be done to manage COPD?
Smoking cessation advice
Bronchodilator therapy - short acting
Combination therapy - long acting B2 agonist, inhaled steroid, long acting anticholinergic
Oral theophylline if others unsuccessful
Home oxygen
258
Give 2 examples of short acting and 2 long acting B2 agonists
Short: salbutamol, terbutaline
Long: salmeterol, formoterol
259
Describe the mechanism of action of B2 agonists
Bind to B2 receptor and activate it which activates adenylate cyclase via G-aS
This increases cAMP levels which activates PKA
This causes phosphorylation of myosin light chain kinase which inactivates it so reducing smooth muscle contraction
260
What are side effects of drugs such as salbutamol?
```
Tremor
Headache
Tachycardia
Cardiac arrhythmia
Peripheral vasodilation
Hypokalaemia
```
261
How can desensitisation of the B2 receptor occur?
Overuse of B2 agonists
| Increased expression and activity of phosphodiesterase which breaks down cAMP
262
Name a short acting and a long acting anticholinergic drug used as bronchodilators
Short: Ipratropium
Long: tiotropium
263
Describe the mechanism of action of anticholinergic drugs as bronchodilators
Antagonist at muscarinic ACh M3 receptor
This prevents Gq from activating phospholipase C
Less PIP3 is converted to IP3 and so less Ca is released from the endoplasmic reticulum
Less Ca available to bind to calmodulin so myosin light chain kinase is not activated and therefore smooth muscle contraction is prevented
264
What are side effects of drugs such as Ipratropium?
```
Dry mouth
Constipation
Cough
Headache
Nausea
Paradoxical bronchospasm
Urinary retention
Glaucoma
```
265
Name 2 methylxanthines used as bronchodilators
Aminophylline, theophylline
266
Describe the mechanism of action of theophylline
Inhibit phosphodiesterase so prevent breakdown of cAMP
| So more PKA can be activated and therefore phosphorylate more myosin light chain kinase
267
What are the side effects of theophylline?
```
Insomnia
Nausea
Vomiting
Cardiac arrhythmias
Seizures
```
268
Why do serum theophylline levels have to be carefully monitored?
Narrow therapeutic range
| Side effects outside this range are toxic
269
What could increase clearance of theophylline from your patient?
```
Drugs: rifampicin, anticonvulsants, phenobarbitone
Ethanol
Tobacco smoking
Childhood
High protein diet
```
270
What could decrease clearance of theophylline from your patient?
```
Drugs: cimetidine, erythromycin, zafirlukast
Old age
Congestive heart failure
Liver cirrhosis
Respiratory acidosis and pneumonia
Viral hepatitis
High carb diet
```
271
Name 2 leukotriene antagonists used as bronchodilators
Montelukast
| Zafirlukast
272
Describe how leukotriene antagonists work
Block CysLT1 receptors
Leukotrienes cause airway inflammation and bronchospasm so antagonises this
Reduce exercise induced symptoms in asthma
Reduce inflammatory response
Used as a preventer
273
Name 2 inhaled, 1 oral and 1 IV glucocorticoid used in treatment of asthma
Inhaled: Beclomethasone, Fluticasone
Oral: prednisolone
IV: hydrocortisone
274
Describe the mechanism of action of glucocorticoids in treatment of asthma
Activate intracellular glucocorticoid receptor which interacts with DNA and influences gene expression
Inhibits formation of pro inflammatory products - cytokines, IL3/5, PGE2
Increases expression of anti inflammatory products - upregulates B2 receptor
275
What are side effects of glucocorticoids?
```
Central weight gain
Moon face
Easy bruising
Poor wound healing
Muscle wasting of arms and legs
Thinning of skin
Hypertension
Buffalo hump
Euphoria
```
276
What are mast cell stabilisers?
Sodium cromoglicate and nedocromil
Stabilise membranes of mast cells to prevent histamine release
Useless in acute exacerbation
Side effect - bitter taste
277
What is Omalizumab?
Monoclonal anti- IgE antibody
Useful to prevent allergic asthma
Expensive so only used if patient on regular corticosteroids and if manufacturer gives agreed discount in patient access scheme
278
How big is the anatomical dead space/conducting airways?
150ml
279
How big are the respiratory parts of the lungs?
3L
280
What parts of the respiratory system make up the conducting airways?
```
Nasal cavities
Nasopharynx
Oropharynx
Larynx
Trachea
Bronchi
Bronchioles
Terminal bronchioles
```
281
What parts of the respiratory system make up the respiratory airways?
Respiratory bronchioles
Alveolar ducts
Alveolar sacs
Alveoli
282
What are keratinised squamous epithelium?
Protected from abrasion by keratin and kept hydrated by glycolipids produced in stratum granulosum
Lines vestibules - first 1.5cm of conductive portion following nostrils
283
What is non-keratinised squamous epithelium?
Oropharynx and larynx lined with this cell type
| Must be kept moist by bodily secretions to prevent drying out
284
What is another name for pseudostratified ciliated epithelium?
Respiratory epithelium
285
What are the layers of the trachea?
Mucosa
Submucosa
Muscularis
Cartilaginous rings
286
Which side of the trachea is flattened?
Posterior, facing oesophagus
287
How long is the trachea?
10cm
288
What type of cartilage is tracheal cartilage?
Hyaline
289
What type of epithelium lines the trachea?
Pseudo stratified ciliated epithelium, respiratory epithelium
290
What cell types are present in bronchi?
```
Respiratory epithelium
Goblet cells
Submucosal glands
Smooth muscle between mucosa and cartilage plates
Cartilage plates
```
291
Describe the structure of the bronchioles
```
Less than 1mm in diameter & no cartilage
No mucous glands
Ciliated low columnar
Epithelium
Increasing numbers of clara cells distally (dome shaped cells with small microvilli, simple epithelium, protect bronchioles)
Smooth muscle is major wall component
```
292
Describe structure of terminal bronchioles
Cuboidal epithelium with few ciliated cells and abundant Clara cells
Smooth muscle knobs
293
What non respiratory cells are present in conducting airways?
Neuroendocrine cells - Scattered throughout the basal layer, Dense core granules, Bombesin, substance P, calcitonin an leu-encephalin, Involved in development and regeneration / repair
Brush cells - Microvilli resemble small intestinal enterocytes, Function not entirely clear ?absorb water
Basal cells - Stem cells of airway, adhesion to basement membrane
Clara cells - Terminal bronchioles, Act as stem cells, modulating inflammation, anti-oxidant andanti protease activity
294
Describe the different roles of type I and type II pneumocytes
Type I pneumocytes - gas exchange
| Type II pneumocytes - Regeneration and surfactant production
295
What cells are present in alveoli?
Type I and II pneumocytes, endothelium, alveolar macrophages
296
What is surfactant?
Lipid rich secretion reducing surface tension
| Recycled by type 2 pneumocytes
297
What do alveolar macrophages do?
```
Recruited from blood as monocytes
Main phocytic cell of the lung
Remove the majority of foreign material entering alveoli
More numerous in smokers
Aerobic metablolism
Dense lysosomal bodies
Phagocytic vacuoles
Most removed by mucociliary escalator
Some migrate to hilar nodes
```
298
What is chronic bronchitis?
Clinical diagnosis productive cough 3 months of the year 2 consecutive years
Hypersecretion of mucus
Hypertrophy of bronchial mucus glands (Reid Index postmortem)
Hyperplasia of goblet cells
Mild dilatation of bronchi
299
What effects does smoking have on the lungs?
```
Loss of cilia
Squamous metaplasia
Mucous hypersecretion
Goblet cell hyperplasia
Individual factors affect the extent and rate of these changes
```
300
What is smog and what effect can it have on the lungs?
Industrialisation
Increase in particulate matter in the atmosphere
Irritation of the bronchial epithelial lining leading to brochitis
301
What is small airways disease?
Chronic obstructive bronchiolitis
Small bronchi and proximal bronchioles 9th order airways 2mm diameter
Goblet cell hyperplasia of bronchioles
Loss of clara cells (secrete protease inhibitors) Smoking related
Fibrosis, wall thickening and focal stenoses
302
What is emphysema?
```
Bronchioles collapse due to loss of parenchyma
Air trapping on expiration
Exacerbated by airway secretions
Barrel chest
Flattened diaphragm
```
303
What patterns of emphysema are there?
Centriacinar
Paraseptal
Pan acinar
Irregular
304
What is aspiration pneumonia?
Lower respiratory tract infection resulting from the inhalation of material, e.g. food/drink, from oropharynx and gastrointestinal tract into the respiratory tract (aspiration). The lungs are normally protected against aspiration by protective reflexes such as coughing
