ASTHMA
ATOPY, ALLERGY AND ASTHMA
Asthma is a heterogeneous condition of different clinical phenotypes, with wheezing being the major clinical expression. Two wheezing phenotypes have been identified in children with asthma:
1. IgE-mediated wheezing (atopic asthma)
2. Nonatopic wheezing in the preschool and school going child.
Another wheezing phenotype is a transient wheeze or happy wheezer which is not a genuine asthma although wheeze occurs due to recurrent viral infection in infants with congenital narrow airway caliber. Nonatopic Wheezing Nonatopic wheezers have normal lung function early in life, but a lower respiratory illness due to a viral infection (usually RSV) leads to increased wheezing during the first 10 years of life. This phenotype seems to cause less severe persistent wheezing, and symptoms improve during adolescence. IgE-mediated Wheezing (Atopic Asthma) Atopic wheezing is the usual perception of asthma. Lung function is normal at birth, but recurrent wheeze develops with allergic sensitization, with increased blood IgE and positive skin prick tests to common allergens. Atopic wheezers have persistence of symptoms and have decreased lung function later in childhood. Risk factors for the development of atopic wheeze (asthma) are family history of asthma or allergy and a history of eczema. Atopy and Allergy Atopy is an inherited predisposition to sensitization to allergens, and is present in up to 40% of children, most of whom are asymptomatic. Atopic children are at increased risk of allergic disease. The presence of one allergic condition within a child increases the risk of another; for example, half of children with allergic asthma will have eczema at some stage during their lives. Allergic disorders are:
1. IgE-mediated wheezing (atopic asthma)
2. Nonatopic wheezing in the preschool and school going child.
Another wheezing phenotype is a transient wheeze or happy wheezer which is not a genuine asthma although wheeze occurs due to recurrent viral infection in infants with congenital narrow airway caliber. Nonatopic Wheezing Nonatopic wheezers have normal lung function early in life, but a lower respiratory illness due to a viral infection (usually RSV) leads to increased wheezing during the first 10 years of life. This phenotype seems to cause less severe persistent wheezing, and symptoms improve during adolescence. IgE-mediated Wheezing (Atopic Asthma) Atopic wheezing is the usual perception of asthma. Lung function is normal at birth, but recurrent wheeze develops with allergic sensitization, with increased blood IgE and positive skin prick tests to common allergens. Atopic wheezers have persistence of symptoms and have decreased lung function later in childhood. Risk factors for the development of atopic wheeze (asthma) are family history of asthma or allergy and a history of eczema. Atopy and Allergy Atopy is an inherited predisposition to sensitization to allergens, and is present in up to 40% of children, most of whom are asymptomatic. Atopic children are at increased risk of allergic disease. The presence of one allergic condition within a child increases the risk of another; for example, half of children with allergic asthma will have eczema at some stage during their lives. Allergic disorders are:
• Asthma
• Eczema
• Allergic rhinitis
• Allergic conjunctivitis
• Urticaria and angioedema
• Food and drug allergies.
Differential Diagnosis of Childhood Asthma Causing Recurrent Wheeze in Infancy
•Bronchiolitis
•Happy wheezers
•Postbronchiolitis wheeze
•Viral croup
•Gastroesophageal reflux disease (GERD)
•Cystic fibrosis
•Pulmonary TB
•Laryngotracheomalacia
•Bronchiectasis
•Postnasal drip syndrome
•Recurrent pneumonia
•Inhaled foreign body
•Recurrent aspiration of food.
Triggers of Asthma
•URTI—viral infection, common cold
•Changes in season, weather and temperature
•Indoor allergens:
– House dust mite (Fig. 20)
– Dander or flakes
—from the skin, hairs or feathers of warm-blooded pets (dogs, cats, birds, rodents, etc.)
– Molds—harbored in vacuum cleaner, air conditioners, humidifier
– Insects—cockroach
•Outdoor allergens:
– Pollens—from grass, flowers, trees
– Molds of some fungi
•Stress: Emotion, surgery, pregnancy
•Irritants (more generalized):
– Tobacco smoke – Wood smoke
– Strong odors, perfumes and spray, cosmetics, paints, cooking especially with spices
•Certain drugs—ß-blockers, aspirin, NSAIDS
•Food allergens—rarely cause an asthmatic attack.Beef, prawn, hilsa, duck egg, nuts, some vegetables, etc
DIAGNOSIS OF ASTHMA
The diagnosis of asthma is clinical. The diagnosis of asthma in children should be suspected in any child with wheezing on more than one occasion, ideally heard on auscultation by a health professional, and distinguished from transmitted upper respiratory noises. Wheezing is a whistling noise heard from the chest, and parents’ perception of wheezing often varies from health professionals. In practice, the diagnosis is usually made on a history of recurrent wheeze, with exacerbations usually precipitated by viral respiratory infections
The diagnosis of asthma is clinical. The diagnosis of asthma in children should be suspected in any child with wheezing on more than one occasion, ideally heard on auscultation by a health professional, and distinguished from transmitted upper respiratory noises. Wheezing is a whistling noise heard from the chest, and parents’ perception of wheezing often varies from health professionals. In practice, the diagnosis is usually made on a history of recurrent wheeze, with exacerbations usually precipitated by viral respiratory infections
. History and Clinical Features:-
•Cough, worse particularly at night disturbing sleep or chronic unproductive cough without apparent cause
•Recurrent wheeze
•Recurrent breathing difficulty
•Recurrent chest tightness
•Family history of allergy or atopy (asthma, eczema, hay fever)
•Personal history of other allergic conditions (dry skin, itchy skin with scratch marks, allergic eye signs, eczema, allergic rhinitis, enlarged adenoids in the same child currently or in the past) (Figs 21 to 23)
•Limitation of physical activities and exercise
•Chest hyperinflation
•Evidence of chest deformity:
– Pectus carinatum
– Harrison sulcus
– Bowing of chest, etc
•Symptom aggravates with triggers reversible at least partially by drugs (bronchodilators) The pattern of asthma should be assessed by asking following questions:
•How frequent are the symptoms?
•How much school has been missed due to asthma?
•Are sport and general activities affected by the asthma?
•How often is sleep disturbed by asthma?
•How severe are the interval symptoms between exacerbations?
On Auscultation
•Poor air entry with prolonged expiration, rhonchi
•Reversible and variable airflow limitation:
– As measured by peak expiratory flow (PEF) meter in any of the following way:
- PEF increases more than 15%, 15–20 minutes after short acting ß2-agonist
- PEF varies more than 20% from morning measurement upon arising to measurements 12 hours later
- PEF decreases more than 15% after 6 minutes of running or exercise—exercise-induced asthma.
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