Asthma means ‘laboured breathing’ in Greek and was first described 3000 years ago. It is a broad term used to refer to a disorder of the respiratory system that leads to episodic difficulty in breathing. According to The National (BTS/SIGN) guidelines, asthma is defined as ‘a chronic inflammatory disorder of the airways
Asthma Disease
which occurs in susceptible individuals; inflammatory symptoms are usually associated with widespread but variable airflow obstruction and an increase in airway response to a variety of stimuli. Obstruction is often reversible either spontaneously or with treatment’.
The exact prevalence of asthma remains uncertain because of the differing ways in which airway restriction is reported, diagnostic uncertainty (especially for children under 2 years) and the overlap with other conditions such as chronic obstructive pulmonary disease (COPD). Over 5 million people in the UK have asthma (Asthma UK, 2001) and around 300 million worldwide. Mortality from asthma is estimated at approximately 0.4 per 100,000 with around 1400 deaths per annum in the UK. Most deaths occur outside the hospital; the most common reasons for death are thought to be an inadequate assessment of the severity of airway obstruction by the patient and/or clinician and inadequate therapy with inhaled or oral steroids.
The two main causes of asthma symptoms are airway hyperresponsiveness and bronchoconstriction. Hyperresponsiveness is an increased tendency of the airway to react to stimuli or triggers to cause an asthma attack. Bronchoconstriction is a narrowing of the airways that causes airflow obstruction.
Causes Of Asthma
Possible Triggers are listed below
The function of the lungs can be measured to help diagnose and monitor various respiratory diseases. A series of routine tests has been developed to assess asthma as well as other respiratory diseases such as COPD.
The most useful test for abnormalities in airway function is the forced expiratory volume (FEV). This is measured by means of lung function assessment apparatus such as a spirometer. The patient inhales as deeply as possible and then exhales forcefully and completely into a mouthpiece connected to a spirometer. The FEV1 is a measure of the FEV in the first second of exhalation. The forced vital capacity (FVC) can also be measured, which is an assessment of the maximum volume of air exhaled with a maximum effort after maximum inspiration. The FEV1 is usually expressed as a percentage of the total volume of air exhaled, reported as the FEV1 /FVC ratio. This ratio is a useful and highly reproducible measure of the capabilities of the lungs. Normal individuals can exhale at least 70% of their total capacity in 1 s. In obstructive lung disorders, such as asthma, the FEV1 is usually decreased, the FVC normal or slightly reduced and the FEV1 /FVC ratio decreased, usually <0.7
As asthma involves inflammation and bronchoconstriction, treatment should be directed towards reducing inflammation and increasing bronchodilation. Treatment aims should include a lack of day and nighttime symptoms, no asthma exacerbations, no need for rescue medication, normal PEFs and no unwanted side effects from medication (BTS/SIGN). Anti-inflammatory drugs should be given to all but those with the mildest of symptoms. Other measures, such as avoidance of recognized trigger factors, may also contribute to the control of this disease. The lowest effective dose of drugs should be given to minimize short-term and long-term side effects. It should, however, always be remembered that asthma is a potentially life-threatening illness, is often undertreated and not all patients will achieve optimal control.
Short-acting β-adrenoceptor agonist bronchodilators. β-Adrenoceptor agonists are the mainstay of asthma management. Salbutamol and terbutaline are selective β2 -agonists and have few β1 -mediated side effects such as cardiotoxicity. β2 -Receptors are, however, also present in myocardial tissue; cardiovascular stimulation resulting in tachycardia and palpitations is still the main dose-limiting toxicity with these agents when used in high dosage