Obstructive Airway Diseases Flashcards
Explain obstructive lung disease and FEV1/FVC
There is an airflow restriction
Peak expiratory flow rate is reduced
FEV1 is reduced
FVC may be reduced
FEV1 is less than 70% of FVC
What is normal Peak expiratory flow rate (PEFR)?
Normal is between 400-600 L/min
Normal range us 80-100% of best value
Explain bronchial asthma
Type 1 hypersensitivity in the airways
Mast cell degranulation due to IgE, drugs, chemicals..
This causes smooth muscle contraction and inflammation of mucosa
This causes narrowing of airway
These are reversible
What are the main causes to chronic bronchitis and emphysema?
Smoking (vaping)
Atmospheric pollution
Occupation
Alpha -1 antitrypsin
Age and susceptibility
Prevalence - men over women
What is chronic bronchitis described as clinically?
Cough productive of sputum most days in at least 3 consecutive months for 2 or more consecutive years
Clinically can be confused with Chronic bronchial asthma
What are the morphological changes in chronic bronchitis?
Large airways - mucous gland hyperplasia, goblet cell hyperplasia and inflammation and fibrosis is minor
Small airways - goblet cells appear and inflammation and fibrosis in long standing disease
What is the definition of emphysema?
Arise dilatation or from destruction of their walls and without obvious fibrosis
Increase in size of airspaces distal to the terminal bronchiole
Explain the form of emphysema - Centriacinar?
Begins with bronchiolar dilation, then loss of alveolar tissue
Holes develop in the centre of the acinus
What are the cases of emphysema?
Smoking
Protease - Antiprotease imbalance
Ageing
Alpha-1 antitrypsin deficiency
Explain the anti-elastase and elastase balance in a normal individual?
Control of elastase-mediated degradation of elastic tissue in the lung requires both an optimal concentration and function of anti-elastase
Elastic framework of the alveolar tissue is then maintained
What would happen if an individual has an alpha-1 antitrypsin deficiency?
If the bod does not have AAT then the lung is not as protected from elastase enzymes. These enzymes break down tissue in alveoli leading to emphysema
How does smoking affect the anti-elastase and elastase balance?
Smoking decreases anti-elastase production so elastase increases and favours elastin destruction.
Also increases neutrophils and macrophages and removes any repair mechanisms of elastin synthesis.
Is airway obstruction in COPD irreversible?
Not fully reversible but there may be a reversible component. Traditionally considered irreversible
What parts of small airways in emphysema can respond to pharmacological intervention?
Smooth muscle tone
Inflammation of small airways
Why do patients get hypoxaemia in COPD?
Airway obstruction
Reduced respiratory drive
Loss of alveolar surface area
Shunt - only during severe acute infective exacerbations
