ASTHMA

A. K. Nayyar

Definition

• It is a syndrome characterized by AIRFLOW OBSTRUCTION that varies markedly, both spontaneously and with treatment.

• Narrowing of the airways is usually reversible, but in some patients with chronic asthma there may be an element of irreversible airflow obstruction

Cont.

• It is characterized

• pathologically by bronchial inflammation with prominent eosinophil infiltration physiologically by bronchial hype-reactivity, and

• clinically by variable cough, chest tightness and wheeze

Epidemiology

• It affects approximately 10-15% of children and 5-10% of adults

• Prevalence is greater in industrialized countries

• Prevalence is increasing world-wide

Pathology of asthma

• Infiltration with inflammatory cells (esp. eosinophils and T-lymphocytes)

• Patchy epithelial shedding

• Airway smooth muscle thickening

• Subepithelial fibrosis

• Mucus gland and goblet cell hyperplasia

• widespread mucus plugging in fatal asthma

Mechanisms of asthma

• Inflammation underlies airway hyperresponsiveness

• The inflammation is of characteristic pattern and it involves interaction between many inflammatory cells

• This results in the release of multiple inflammatory mediators

• Inflammatory mediators result in bronchoconstriction, mucus secrition, exudation of plasma and airway hyperresponsiveness

Cont.

• Neural mechanism may amplify the asthmatic inflammation

• Structural changes may occur with subepithelial fibrosis, airway smooth muscle hyperplasia and new vessel formation. These changes may underlie irreversible airflow obstruction

Types of asthma

• Allergic (extrinsic) asthma

• Non-allergic (intrinsic) asthma

• Occupational asthma

• Aspirin induced asthma

• Asthma of infancy(<2 yr of age)

Allergic asthma

• Onset usually in childhood

• May persist into adulthood

• Remission in adolescence is common

• Associated with allergic rhinitis and atopic dermatitis in variable combination

Intrinsic asthma

• Onset in adults

• No external inciter is recognized

• Often associated with perennial non-allergic rhinitis

• Accounts for approx. 10% of adult asthma

Occupational asthma

• Due to exposure to chemical sensitizers at work

• Unrelated to atopic status

• Some occur in atopics due to allergen exposure at work

Aspirin induced asthma

• Special type of intrinsic asthma

• It is a metabolic, pharmacological disorder

• acute asthma attacks on first and subsequent exposure to aspirin and NSAID

Asthma of infancy

• Recurrent bouts of significant airflow limitation in small airways from viral infections

• Often remits as child gets older

• not associated with atopy

• Sometimes called wheezy bronchitis

Clinical features

• Symptoms

• Triggers

• Physical signs

Symptoms

• Wheeze-- intermittent, worse on expiration, chracteristically relieved by an inhaled β2- agonist

• Cough-- usually unproductive

• Chest tightness

• SOB

• Prodromal symptoms may precede an attack

Triggers

• Allergens (house dust mite, pollen, animal dander, moulds)

• Irritants (tobacco smoke, air pollutants, strong odours, fumes)

• Physical factors (exercise, cold air, hyperventillation, laughter, crying)

• Upper respiratory tract viral infections

• Emotions

• Occupational agents (chemical sensitizers, allergens)

• Drugs (beta blockers,NSAID)

• Food additives (metabisulphite,tartrazine)

• Change in weather

• Endocrine factors (menstrual cycle, pregnancy,thyroid disease)

Physical signs

• Expiratory ronchi- widespread

• Hyperinflation of chest

• Use of accessory muscles

• Associated signs: nasal polyps, flexure eczema

Features suggestive of asthma in young children

• Symptom free intervals• Nocturnal cough• Coughing after exercise• Coughing when laughing or crying• Good response to correctly inhled or nebulized

bronchodilators• Personal or family history of atopic disease• Onset unrelated to respiratory syncytial virus

infection

Features suggestive of alternative diagnosis in young children

• Failure to thrive(? Cystic fibrosis, immunodeficiency)

• Absence of symptom free interval

• Sudden onset of persistent symptoms

• Persistent URTI/ otitis (? ciliary dyskinesia)

• Vomiting / recurrent pneumonia(? Acid reflux, aspiration)

• Premature birth (?bronchopulmonary dysplasia)

• Onset in RS virus season(?Post RSV broncholitis)

DD in adults

• Mechanical obstruction of airways

• COPD

• Heart failure

• PE

• Vasculitides

• Carcinoid syndrome with hepatic secondaries

Principles of treatment

• Educate patients to develop a partnership in asthma management

• Assess and monitor severity with objective measurement of lung function

• Avoid or control asthma triggers• Establish medication plans for chronic

management• Establish plans for managing exacerbations• Provide regular follow-up care

Clinical evaluation of severity

• Number of daytime attacks lasting more than 24 hrs and needing extra medication

• The presence of completely symptom-free intervals lasting more than 4 weeks without medication

• The frequency of waking at night due to asthma symptoms• The amount of absence from work or school because of asthma• The ability of the patients to keep up with peers in normal physical

activity• The number and type of medications required on regular basis• The frequency of using extra relief medications on an ‘as needed’

basis• The frequency of hospital admission• The of life-threatening episodes