Obstructive Airway Diseases Flashcards
Name 3 obstructive airway diseases
Chronic Bronchitis
Emphysema
Asthma
Chronic Obstructive Pulmonary Disease (COPD) is the name more commonly known for what diseases?
Chronic Bronchitis
Emphysema
What is FEV1?
The forced expiratory volume
What is the normal FEVE1 volume?
3.5 - 4 litres
What is the normal FVC volume?
About 5 litres
What is the normal ratio of FEV1 : FVC?
0.7 - 0.8
What is the normal peak expiratory flow rate (PEFR)?
400-600 litres/min
What is the normal range of PEFR (as a percentage of best value)?
80-100%
What effect do obstructive lung diseases have on:
PEFR
FEV1
FVC
PEFR - reduced
FEV1 - reduced
FVC - may be reduced, may be normal
What causes bronchial asthma?
Type I sensitivity in the airways
Bronchial asthma is driven by what?
Mast cell degranulation
What two groups of chemicals are released due to degranulation?
Chemotactic factors
Spasmogens
What does bronchial asthma cause the cross-sectional area of the lumen in small bronchioles to do?
Reduce
Is bronchial asthma generally considered to be reversible or irreversible?
Reversible
What effect does bronchial asthma have on bronchial smooth muscle?
Bronchial asthma causes contraction and inflammation of the bronchial smooth muscle
Give a cause of COPD?
Smoking
Atmospheric pollution
Occupational pollution (e.g. asbestos)
Ageing
(Alpha-1-antiprotease (antitrypsin) deficiency = very rare cause of emphysema)
What morphological changes occur in the large airways in chronic bronchitis?
Mucous gland hyperplasia
Goblet cell hyperplasia
inflammation and fibrosis (minor component)
What morphological changes occur in the small airways in chronic bronchitis?
Goblet cells appear
Inflammation and fibrosis in long standing disease
Emphysema is an increase beyond normal in the size of airspaces distal to the terminal bronchiole arising from
Dilatation
or
destruction of their walls
What type of emphysema begins with bronchiolar dilatation followed by loss of alveolar tissue?
Centri-acinar Emphysema
What is Panacinar Emphysema characterised by?
Permanent destruction of the entire acinus distal to the respiratory bronchioles
No obvious associated fibrosis
What is Bullous Emphysema characterised by?
The presence of one or more abnormally large air spaces surrounded by relatively normal lung tissue
What is a Bulla?
An emphysematous space greater than 1cm
What is a “bleb”?
An emphysematous space greater than 1cm (a bulla) just underneath the pleura
What components of small airways have been found to respond to pharmacological intervention?
Smooth muscle tone
Inflammation
What value of PaO2 is seen in type I respiratory failure?
PaO2
What is the value of PaCO2 in type I respiratory failure, compared to normal?
Normal or low
What is the value of PaCO2 in type II respiratory failure?
PaCO2 > 6.5 kPa
What is the value of PaO2 in type II respiratory failure compared to normal?
(usually) low
What are the four abnormal states associated with Hypoxaemia?
- Ventilation/Perusion imbalance (V/Q)
- Diffusion Impairment
- Alveolar Hypoventilation
- Shunt
What does a ventilation/perfusion mismatch cause which contributes to COPD?
Airway obstruction
What does diffusion impairment cause which contributes to COPD?
Loss of alveolar surface area
What does alveolar hypoventilation cause which contributes to COPD?
Reduced respiratory drive
When does shunt occur in hypoxaemia?
Only during active ineffective exacerbation
What is the normal ventilation/perfusion ratio?
4/5 (0.8)
What ventilation/perfusion imbalance is the most common cause of hypoxaemia?
Low V/Q
Local alveolar hypoventilation due to some focal disease may cause what to arise in some alveoli?
Low V/Q
Hypoxaemia due to low V/Q responds well to small increases in what?
FIO2
What effect does alveolar ventilation have on PACO2 and PaCO2?
PACO2 - increases
PaCO2 - increases
What effect does increased PACO2 have on PAO2 and PaO2?
PAO2 - decreases
PaO2 - decreases
A fall in PaO2 due to hypoventilation is corrected by raising what?
FIO2
What is FIO2?
The fraction of inspired air which is oxygen
What does hypoxia cause in the pulmonary arterioles?
Vasoconstriction
Pulmonary arteriolar vasoconstriction can be a localised effect, what would cause all vessels will constrict?
Hypoxaemia
Why is vasoconstriction a protective mechanism?
As it stops blood being sent to alveoli that are short of oxygen
What is Chronic Cor Pulmonale?
Hypertrophy of the right ventricle resulting from disease affecting the function and/or structure of the lung
What factors cause Pulmonary Hypertension to occur in Hypoxic Cor Pulmonale?
- pulmonary vasoconstriction
- muscle hypertrophy and intimal fibrosis in pulmonary arterioles
- loss of capillary bed
- secondary polycythaemia
- bronchopulmonary arterial anastamoses
