Respiratory Diseases Flashcards
CHRONIC OBSTRUCTIVE PULMONARY DISEASE (COPD)
- 10% of the world’s pop have COPD
- the common abnormality is a limitation to expiratory airflow, due to narrowing of the airways
- Airway diameter is usually determined by the tone of the bronchial/bronchiolar smooth muscle
- Normally, parasympathetic (bronchoconstrictor) tone dominates sympathetic (bronchodilator) tone
COPD - airway calibre is decreased by:
- Bronchoconstriction
- Oedema - e.g. an allergic reaction
- bronchial secretions e.g. mucus in airways = when airways trying to protect themselves due to an acute problem such as acute bronchitis (infection) or chronic e.g. cigarette smoke
- loss of elastic recoil
Common causes are:
- chronic bronchitis
- Emphysema
ASTHMA
- Constriction of bronchioles narrows airways
Constriction usually results from:
- exposure to allergens
- cold dry air (exercise induced)
In addition to narrowing of airways get:
- increased mucus production
- formation of mucous plugs
- airway oedema (gas movt through narrow airways causes wheezing + mucous causes cough)
Sympathetic + Parasympathetic activity (asthma)
Sympathetic activity → bronchodilation
- Ventolin is a drug that mimics the effects of the sympathetic nervous system (sympathomimetic)
- Treats symptoms
Parasympathetic activity → bronchoconstriction
- Parasympatholytic drugs block the parasympathetic nervous system
- Treat symptoms
Prevent disease using corticosteroids - Becotide (suppresses inflammation)
- Acute asthma can be fatal, associated with hypoxaemia (can’t get enough O2 in blood) + fatigue of respiratory muscles (working much harder as trying to move gas through narrow airways)
- Death often associated with excessive reliance on bronchodilators – these drugs only treat symptoms
- Corticosteroids may create long term benefit by reducing allergy - Becotide
CHRONIC BRONCHITIS
- Narrowing of airways occurs as a result of hypertrophy and hyperplasia of mucus glands
- Increased secretions narrow the airways further
- Usually occurs in smokers - main sign is morning cough
EMPHYSEMA
cause
- Usually develops as a progression of chronic bronchitis
- Caused by elastases resulting from smoking which destroy pulmonary tissue
(elastic tissue does 2 important jobs: 1. Provides the framework on which the alveoli are built, 2. Holds the airways open during expiration = if have CB airways will collapse during expiration = limit expiratory airflow / obstruct airways
~20% of cases due to abnormal enzymes in lung - Main problem is loss of alveoli which decreases the surface area for diffusion - O2 can’t enter blood = limit ability to do PA = reduced pulmonary function
- To maintain diffusion need to increase concentration gradient → treatment is supplemental oxygen
- Emphysema is characterised by increased functional residual capacity → the lungs are relatively “full”
- The diaphragm is therefore flattened
the pressure exerted by a gas mixture…
The pressure exerted by a gas in a mixture of gases is equal to the total pressure multiplied by the fraction of the total pressure it represents
The atomposphere is always 79%N2 and 21% O2
- The pressure O2 to the lungs can be increased by increasing the inspired oxygen concentration
solutions for emphysema
- Loss of elastic tissue causes airway collapse during expiration (airflow obstruction)
- Increasing airway pressure will help keep airways open and allow gas flow to occur
- Pursed lip breathing can be used to achieve this - it increases resistance to expiration. Consequently, expiratory pressure increases
- Elastic force = holds bronchioles open during expiration
2 main changes in emphysema
2 important changes:
- destruction of the alveoli + - closure/compression of the small airways
= limit expiratory airflow
Complications of COPD:
- COPD Exacerbations = mainly due to respiratory infections
- Systemic inflammation
- Skeletal muscle damage = leads to decreased exercise capacity = further loss of respiratory function
PULMONARY REHABILITATION NEEDED = MOST EFFECTIVE
ABNORMAL DIAPHRAGMATIC FUNCTION
- Often associated with COPD that results in fatigue
- Normal contraction of the diaphragm creates a positive intra-abdominal pressure
- This makes the abdomen move outwards on inspiration - this is more noticeable in children
- If it is fatigued the diaphragm will move upwards in inspiration → it is drawn upward by the negative thoracic pressure created by the accessory muscles
- As a result, the abdomen moves inwards during inspiration
RESTRICTIVE LUNG DISEASE
The abnormality is a limitation to expansion of the lung due to:
- Diseases of the rib cage
- Diseases of the respiratory muscles
- Diseases of the pleura - pain or compression
- Diseases of lung tissue - stiff lungs
- Osteoporosis - limits chest volumes
characteristics of restrictive lung disease
- There is no limitation to expiratory airflow so FEV1 is normal (or increased) compared with FVC (although the absolute value is decreased)
- The force which is limiting expansion of the chest may facilitate expiration
- FVC will be decreased
- FEV1 will be decreased, but not as much as FVC
- FEV1/FVC normal to increased
FEV1 + FVC of obstructive + restrictive lung problems
Obstruction - problem is getting gas out - gas comes out more slowly
- FEV1 is greatly reduced
- FVC is reduced a little bit/normal
- FEV1/FVC = greatly decreased
- Predicted values FEV1 = 2 | FVC = 5 | FEV1/FVC = 2/4.5 = 0.44
Restrictive - problem is getting gas into the lungs
- FVC = greatly decreased
- FEV1 = normal to decreased
- FEV1/FVC = normal to increased
- Predicted values FEV1 = 4 | FVC = 5 | FEV1/FVC = 0.8
Actual values FEV1 = 2 | FVC = 2 | FEV1/FVC = 1
