L18. Obstructive and Restrictive Lung Disease Flashcards
What clinical commonalities do the diverse ranges of lung pathologies share?
Chronic
Diffuse
Non-infectious
What is the difference between the spirometry of obstructive vs. restrictive lung diseases?
Obstructive: asthma, COPD, brionchiolitis
FEV1 = markedly reduced
FVC = relatively unchanged (Except in severe)
FER = Reduced
Restrictive: Idiopathic lung diseases
FEV1 = relatively normal (can be decreased)
FVC = markedly reduced
FER = often remains normal
What diseases encompass obstructive lung diseases? What are the majority of them caused by?
Asthma
Emphysema
Chronic Bronchitis
Small airways disease
What is chronic obstructive airways disease? COPD?
Often a combination of emphysema, chronic bronchitis and small airways disease.
What are the three types of asthma, and the differences between them?
- Atopic: IgE mediated to specific allergens
- Non-atopic: Not IgE mediated to non-specific allergens
- Other: Not IgE to specific triggers
What are the two temporal responses in asthma? Describe them?
Acute/Immediate: mast cell degranulation: histamine and CLT responses: oedema, bronchospasms and increased mucous production.
Late Response: Epithelial damage and Chemotaxis (eosnophil and cytokine-macrophages) leading to ongoing inflammation.
What are the complications of asthma?
Short term: death, atelectasis (partial collapse or poor lung inflation), spontaneous pneumothorax rare)
Chronic: Airway remodelling (fibrosis and obstruction), chronc hypoxia leading to pulmonary hypertension and cor pulmonale (not very common in asthma)
What is meant by the term status asthmaticus?
Acute, severe asthma that is not responsive to bronchoilators
What is emphysema?
An abnormal, permanent enlargement of air spaces distal to the terminal bronchiole as a result of destruction of the alveoloar wall WITHOUT FIBROSIS
What are the different types of emphysema?
Centriacinar
Panacinar
Distal acinar
Irregular
Describe centriacinar (centrolobar) emphesyma
The most common
Heavily smoking related: smoking causes imbalances of proteases to anti-proteases leading to a net destruction of functional tissue.
An inflammatory response ensues leading to more proteases
Toxins from smoking also directly damage mesenchymal basal (stem) cells leading to overall impaired wound healing ability
What is the macroscopic and microscopic appearances of centriacinar emphysema?
Macroscopically: Formation of big, bubbly airspaces in the lung tissue
Microscopically: loss of alveolar structure (less tissue, more space)
What does emphysema lead to in terms of the mechanics of the lungs?
Causes AIRWAY OBSTRUCTION due to the destruction of elastin and reticulin fibres (loss of ELASTIC RECOIL) in the airways.
Increased risk of COLLAPSE and especially in expiration
What are complications as a result of emphysema?
Hypoxia due to airflow obstruction and loss of diffusion capacity
Pulmonary hypertension leading to cor pulmonale
Pneumothorax
What are the other forms of “ephysema”
Not actually emphysema but classified so because they cause similar respiratory issues:
- Bullous (large cyst formations, prone to rupture)
- Compensatory (increased air capacity of a portion of a lung because another portion has been dysfunctional - distention without destruction)
- Interstitial (air escapes into the soft tissues)
What is chronic bronchitis?
A persistent cough with productive sputum for at least 3 months in 2 consecutive years
It is a chronic inflammation of the LARGER airways that is almost always caused cigarette smoking with increased mucous production and scarring and narrowing.
What is chronic bronchitis characterised by?
Excessive mucous by hypertrophy of mucous secreting glands
calculated by the RIED index of > 0.4 um and increased number of goblet cells
What is the Ried index?
The ratio between the thickness of the glandular layer vs. the distance between basement membrane and the cartilage. The normal value is 0.4 um
Does fibrosis occur in chronic bronchitis?
Yes, it is characterised by peribronchial fibrosis in the small airways
What are some complications of chronic bronchitis?
Superimposed infective exacerbations (chronic infections usually caused by respiratory pathogens - a major cause of hospital admissions)
Hypoxia, pulmonary hypertension, cor pulmonale
Squamous metaplasia, squamous dysplasia, premalignancy
What kind of metaplasia/dysplasia that occurs in chronic bronchitis?
Tall columnar ciliated cells undergoes metaplasia under stress and trauma causing a change to squamous epithelium (tough, resistant phenotype).
An accumulation of mutations: the cells become atypical (morphologically different) = dysplasia which can eventually lead to squamous cell carcinoma
What is chronic obstructive pulmonary disease (COPD)?
> 90% of cases caused by cigarette smoking
Encompasses: emphysema, chronic bronchitis, small airways disease (with some reversible bronchospasm)
What is COPD characterised by?
A slow progression with superimposed infective exacerbations - bacterial bronchitis and increased bronchospasms
Is the mix for the diseases of chronic bronchitis and emphysema even in COPD?
Not necessarily. Different individuals have different profiles for disease.
