Obstructive and Restrictive Lung Diseases Flashcards
How is forced expiratory volume (FEV1) measured?
Using a vitalograph
Outline the pathophysiology of asthma
IMMEDIATE RESPONSE
1. Inhaled allergens bind to the IgE antibody present on mass cells
2. The mast cells release inflammatory mediators such as histamine
3. The inflammatory mediators cause the production of mucus, bronchoconstriction and oedema
DELAYED RESPONSE
1. Eosinophils are activated by the mast cells (chemotactic factors) and discharge proteins that damage the epithelium (eosinophil peroxidase)
2. This damage stimulates afferent nerves which activate parasympthathetic discharge
3. This increase in parasympathetic innervation causes an increase in mucus secretion and airway constriction
What type of condition is asthma?
Type 1 hypersensitivity condition
What allergens may trigger asthma?
Air pollutants, pollens, dust mites, moulds, animals, medications such as aspirin and NSAIDs and some foods
What are the symptoms of asthma?
Coughing at night, during activity, wheezing or chest tightness on allergen exposure and prolonged duration of colds.
What skin conditions may be associated with asthma?
Atopic dermatitis or eczema, believed to be due to type 1 hypersensitivity reactions also, but by unknown mechanisms
What drugs are used to prevent asthma attacks?
Corticosteroids, long-acting beta-2-agonists and leukotriene modifiers to reduce inflammation, relax airway muscles and improve symptoms and lung function
What drugs are usually given to relieve the immediate symptoms of an asthma attack?
Short-acting beta 2 agonists
Why are spacers used in the administration of asthma medication?
These can greatly improve the penetration of inhaled drugs into the lungs and also reduce potential for adverse effects from medication
Why are nebulisers used in the administration of asthma medication?
These are machines that produce an inhaled mist of mediated. They are used for small children or severe episodes of asthma attack.
What is COPD?
A combination of chronic bronchitis and emphysema
What is chronic bronchitis?
Chronic productive cough without clear cause; features include hypertrophy of bronchial glands, hyper secretion of mucus (forming plugs) and infection/inflammation
What is emphysema?
This is where there is destruction of the alveolar walls (stroma) leading to reduced surface area and production of bullae
What are bullae?
Accumulation of several alveoli clumped together due to wall destruction
What is the main cause of emphysema and COPD?
Smoking
What is the pathophysiology underlying (chronic bronchitis)
This condition is part of what makes up COPD; irritants damage the epithelium in the bronchioles and cause the proliferation of squamous cells and stimulation of mucus gland enlargement
What is the pathophysiology of emphysema?
- Cigarette smoke stimulates polymorphonuclear leucocytes (PMN) to release the enzyme serine elastase.
- The smoke also inactivates the elastase inhibitor (1-antitrypsin)
- The inactivation of 1-antitrypsin allows the serine elastase enzyme to destroy the elastic tissues of the lung
- This produces stiffness and emphysema
How can you differentiate between COPD and asthma?
Peak flow increases after salbutamol is given in asthmatics, but not in those with COPD
What is the key feature of restrictive lung disorders?
Reduced vital capacity
How do pneumonia, pneumothorax, atelactis and pulmonary fibrosis lead to reduced vital capacity?
These conditions cause a reduction in lung volume and therefore there is less room for air
How does ankylosing spondylitis and kyphoscoliosis lead to reduced vital capacity?
They involve an external mechanical limitation lung volume
What do flow-volume loops show?
Flow against lung volume (L/sec against L)
Describe a normal flow-volume loop
The bottom represents inspriration
Describe a normal flow-volume loop
The bottom represents inspiration and the top represents expiration:
> The bottom, inspiratory loop should be symmetrical and look like a semi-circle
The top, expiratory curve should rise steeply and fall slowly
How can you determine PEV from a flow-volume loop?
On the superior expiratory curve, the highest point is the peak expiratory flow rate
Generally, how does restrictive lung disease appear on flow-volume loops?
Tall and narrow flow-volume loops
Generally, how does obstructive lung disease appear on flow-volume loops?
There is ‘scooping out’ of the expiratory portion of the loop, the inspiratory portion remains the same
