Pathology of Obstructive Lung Disease Flashcards
Give examples of localised obstructive diseases (not necessarily obstructive diseases)
Lung cancer and other tumours, inhaled foreign bodies and chronic scarring diseases (bronchiecstasis and secondary tuberculosis)
What are the three main obstructive airway diseases?
Chronic bronchitis Emphysema Asthma (Mechanisms for each are different)
What is Chronic Bronchitis and Emphysema also known as?
COPD
What are the normal values for FEV1, FVC and the ratio between them?
Normal FEV1 is about 3.5 – 4 litres Normal FVC is about 5 litres Normal ratio FEV1 : FVC is 0.7 – 0.8
What is used to predict FVC?
Age, sex and height
Besides FEV1/FVC ratio, how else can an obstructive lung disease be demonstrated?
Peak expiratory flow rate
What are the normal values for PEFR?
Normal 400 – 600 litres/min Normal range is 80-100% of best value
What is a moderate fall in PEFR?
50-80% of best
What is a marked fall in PEFR?
<50% of best is a marked fall
What is FEV1, FVC, and PEFR in obstructive lung diseases?
There is AIRFLOW LIMITATION Peak Expiratory Flow Rate (PEFR) is reduced FEV1 is REDUCED FVC may be reduced FEV1 is less than 70% of FVC
What causes the decrease in diameter size in bronchial asthma?
Degranulation of mast cells and smooth muscle contraction (both reversible by use of drugs, or spontaneously)
What type of hypersensitivity is bronchial asthma?
Type 1
What physical substances obstruct airways in chronic asthma?
Oedema, mucus, plasma exudation
What are the aetiologies of chronic bronchitis and emphysema?
SMOKING Atmospheric Pollution Occupation : dust
What is the effect of smoking on alpha-1-antiprotease (antitrypsin)?
Malfuntion of antitrypsin (alpha-1-antiprotease) -= emphysema or COPD
What is the result of antitrypsin deficiency?
Neutrophil elastase is free to break down elastin, which contributes to the elasticity of the lungs. Antitrypsin would normally It protect tissues from enzymes of inflammatory cells, especially neutrophil elastase
How does FEV1 change with age?
Reduces
What is chronic bronchitis defined as clinically?
It protects tissues from enzymes of inflammatory cells, especially neutrophil elastase
What does chronic bronchitis exclude?
TB Bronchiecstasis These may be confused with asthma
What is acute exacerbation of COPD?
Sudden worsening of COPD symptoms (shortness of breath, quantity and colour of phlegm) that typically lasts for several days. It may be triggered by an infection with bacteria or viruses or by environmental pollutants. Infection is most common cause (75%)
How does the frequency of exacerbations change as the COPD progresses?
Exacerbations become more and more frequent
What are the morphological changes in large airways in chronic bronchitis?
Mucous gland hyperplasia Goblet cell hyperplasia Inflammation and fibrosis (minor component)
What are the morphological changes in small airways in chronic bronchitis?
Goblet cells appear Inflammation and fibrosis in long standing disease
What is the pathological definition of emphysema?
Increase beyond the normal in the size of airspaces distal to the terminal bronchiole arising from wither dilation or from destruction of their walls without obvious fibrosis. Loss in alveolar tissue, more space between alveoli.
Define acinus
A region of the lung supplied with air from one of the terminal bronchioles
Define centriacinar emphysema
Most common type of pulmonary emphysema mainly localized to the proximal respiratory bronchioles with focal destruction and predominantly found in the upper lung zones. This is because most material inhaled ends up here - max inflammation and destruction occurs here
What is a secondary pulmonary lobule?
The subsegment of lung supplied by three to five terminal bronchioles and separated from adjacent secondary lobules by intervening connective tissue (interlobular septa)
Define panacinar emphysema
Emphysema affecting all parts of the secondary pulmonary lobule, typically involving the inferior part of the lung and often asociated with a α1-antitrypsin deficiency.
What is a Bulla?
Emphysematous space greater than 1 cm
What is a bleb?
A Bulla just underneath the pleura
What is the pathogenesis of Emphysema?
Smoking (Protease - Antiprotease imbalance) Ageing Alpha-1-antitrypsin deficiency
How does antitrypsin deficiency affect this diagram?
Anti-elastase (anti-proteases are reduced)
How does smoking affect this diagram?
Decrease in anti-elastase
Increase in Elastase and neutrophils and macrophages
Decrease in the activity of Repair mechanisms and Elastin synthesis
What portion of COPD is reversible?
Smooth muscle tone and inflammation
What are the normal reference ranges of PaO2 and PaCO2?
What are the two types of respiratory failure?
What are the common causes of Hypoxaemia?
Ventilation/perfusion imbalance
Diffusion impairment
Alveolar Hypoventilation
Shunt
How does COPD involve V/Q mismatch, aveolar ventilation, diffusion impairment and shunt?
Airway obstruction
Reduced Respiratory Drive
Loss of alveolar surface area
Shunt only during acute infective exacerbation
Why does pneumonia cause hypoxaemia?
Ventilation / perfusion abnormality (mismatch) - some ventilation of abnormal alveoli just not enough
Shunt - No ventilation of abnormal alveoli
What is the commonest cause of hypoxaemia clinically?
LOW V/Q
What is the normal percent of blood that is shunted?
2-4%
What is meant by Shunt?
•Blood passing from Right to Left side of Heart WITHOUT contacting ventilated alveoli
Why does shunt respond poorly to increase in FI O2?
•Blood leaving normal lung is already 98% saturated
What is the effect of hypoventilation on PACO2 and PAO2?
- Hypoventilation increases PACO2, and thus increases PaCO2
- Increase in PACO2 decreases PAO2, which causes PaO2 to fall
How do you correct a fall in PaO2 due to hypoventilation?
•Raising FIO2
What causes physiological pulmonary vasoconstriction?
When alveolar oxygen tension falls
How is Physiological pulmonary arteriolar vasoconstriction protective?
Do not send blood to alveoli short of oxygen
What is cor pulmonale?
Hypertrophy of the RV resulting from disease affecting the function and/or structure of the lung
Except where pulmonary alterations are the result of diseases primarily affecting the left side of the heart or congenital heart disease
What causes pulmonary hypertension?
Pulmonary vasoconstriction
Pulmonary arterioles - muslce hypertrophy and intimal fibrosis
Loss of capillary bed
Secondary polycthaemia
