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Asthma Diagnosis
A diagnosis of asthma should be considered if the
following features are present:
History
Presence of atopy i.e. history of asthma, allergic rhinitis, atopic dermatitis, eczema or urticaria in any of the family members.
Dyspnoea with wheezing, which may be episodic initially and continuous later.
Unexplained cough with or without viscid sputum.
Past diagnosis of frequent "allergic bronchitis", "asthmatic bronchitis" or "eosinophilla".
Physical examination
- General: Tachypnoea, tachycardia, use of accessory muscles of respiration, subcostal or intercostals retraction (These are signs of acute episodic attack of asthma).
- Lungs: Since asthmatic symptoms are variable through the day, the physical examination of the respiratory system may appear normal. The combination of hyperinflation and advanced airflow limitation in an asthma exacerbation also markedly increases the work of breathing.
Clinical signs of dyspnoea
- Prolonged expiratory phase associated with
wheezing and hyperinflation is more likely to be present if patients are examined during symptomatic periods and in the morning prior to the administration of a bronchodilator. Wheezing sound is caused by passage of the air current through bronchi narrowed by exudates.
- Sonorous and sibilant rhonchi: musical or wheezing sound when produced in the large bronchi with a deep toned note is sonorous rhonchi. When arising in smallest bronchi with a high pitched squeak its sibilant rhonchi.
Rhonchi are often more consipicious during
expiration because then the bronchi are normally narrower than during inspiration and they are
vesicular in character.
- In a severe attack cyanosis may also be seen.
Cyanosis is a blue discolouration of the skin or mucosa and is usually a sign of severe oxygen
deficiency. It is of central type in Asthma due to
deficient oxygenation of blood in the lungs resulting from inadequate ventilation of perfused areas of lung.
- The percussion note may be hyper resonant.
- Clubbing of fingers may be present when Asthma occurs as a complication of or is associated with
bronchiectasis and bronchial carcinoma.
Investigation
- Normal chest radiogram, which may show enhanced vascular markings.
- Peripheral smear showing Eosinophilia.
- Pulmonary function test: low FEV / FVC ratio.
FVC= The maximum amount of air forcefully expired after maximum inspiration
FEV = The amount of air forcefully expired in the
first second of an FVC
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