Pathology of obstructive lung disease Flashcards
How can obstructive lung disease be demonstrated?
Via spirometry: % of predicted (based off of age, sex, height)
In obstructive lung disease FEV1 < 70% FVC
Peak expiratory flow rate
- normal = 400-600L
- 50% - 80% = moderate fall
- <50% = marked fall
Explain type 1 hypertension in airways
Smooth muscle constricts and inflammation of mucosa = narrowing of lumen and leading to airflow limitation.
What is type 1 hypertension mediated by?
Degradation of mast cells caused by:
- IgE
- Chemicals
- Cold air
- Stress
Describe bronchial asthma
Reversible airway obstruction either spontaneously or as a result of medical intervention.
Bronchial smooth muscle contraction and inflammation can be modified by drugs.
What is the clinical definition of chronic bronchitis?
Cough productive of sputum most days in at least 3 consecutive months for 2 or more consecutive years
What are the signs of complications with chronic bronchitis?
- Mucopurulent sputum (green/yellow)
- FEV1 falls
What happens in the large airways with chronic bronchitis?
Mucous gland hyperplasia
Goblet cell hyperplasia
Inflammation and fibrosis is minor
What happens in the small airways with chronic bronchitis?
Goblet cells and mucous secreting cells appear (as defence mechanism but end up causing the disease).
Inflammation in long standing disease
What is emphysema?
Increases beyond normal size of airspaces distal to the terminal bronchiole arising from either dilation or from destruction of their walls and without obvious fibrosis.
- No fibrosis
- Destruction and loss of alveolar tissue
What is the acinus?
Bit of the lung supplied by the terminal bronchiole (all of the alveoli it supplies).
What are the different forms of emphysema?
Centriacinar
Panacinar
Scar “irregular”
Describe centriacinar
Most clinically important
Common in those who smoke
Begins with bronchial dilation and then alveolar tissue is lost.
Greatest effect on upper lobes of the lungs
Describe panacinar
Affects lower lobes of the lungs
Caused by smoking
Whole wipe out of lung acinus
Describe scar (“irregular”)
Bullous emphysema
- Bulla = emphysema space > 1cm
- May rupture and lead to spontaneous pneumothorax
Why do lungs hyperinflate in obstructive lung disease?
Easier to breath with half inflated lungs as airways are kept half open.
What causes emphysema?
SMOKING
- protease-antiprotease imbalance
Aging
Alpha-1-antitrypsin deficiency
What happens in a normal lung?
Neutrophils and macrophages keep lungs clean/healthy
Anti-elastase (anti-proteases) make elastase making elastin framework in alveolar tissue.
What happens with alpha-1-antitrypsin deficinecy?
Increased production of neutrophils and macrophages
Increased production of anti-elastase (anti-proteases)
Tissue destruction = emphysema
What happens to a smokers lungs in emphysema?
Smoking increases numbers neutrophils and macrophages increased elastase (proteases)
Decreases anti-elastase (anti-proteases)
Leads to tissue destruction = emphysema
What is the mechanism of obstruction in COPD?
Large airways
- little contribution by glands and mucous
Small airways
- Smooth muscle tone
- Inflammation
- Fibrosis
- Partial collapse of airway wall on expiration
In emphysema LOSS OF ALVELOI ATTATCHAMENTS is most important.
What is the importance of alveoli attachments?
There is no cartilage in small airways to keep them open.
Instead they stay open by alveoli attachments (elastic) stretching
If these are wiped out then terminal bronchioles collapse earlier during expiration.
Why does hypoxaemia occur? (4)
- Airway obstruction
- Reduced respiratory drive (don’t breath enough and CNS becomes inured to elevated CO2 and H+ levels in the CSF).
- Loss of alveolar surface area
- Shunt (only during severe acute infective exacerbations)
What is cor pulmonale?
Hypertrophy of the right ventricle resulting from disease affecting the function and/or the structure of the lung.
The right side of the heart becomes dilated and patient can suffer right heart failure.
Describe pulmonary hypertension and how it occurs?
1) Loss of alveoli
2) Loss of blood vessels for blood to go through
3) Bone marrow produces more RBCs
4) Increased blood viscosity due to more RBCs
5) Harder to pump blood through the remaining vessels
