BRONCHIAL ASTHMA

DEFINITION Asthma is a chronic inflammatory lung disease characterized by  symptoms of cough, wheezing, dyspnoe and chest tightness that occur in paroxysms and are related to specific triggering events  airway narrowing that is partially or completely reversible  increased airway responsiveness to a variety of stimuli

over the years the incidence is progressively increasing  Several hypothesis have been proposed to explain the increased frequency in all age groups 1—improved hygeine resulting in less exposure to infectious pathogens and an imbalance in the normal immune response 2—increased indoor air pollution by --recycled air from air conditions --increased allergens—cockroaches, dust mites,pets --irritant gases --cigarette smoke 3—increased incidence of early onset of respiratory viral infections

CARDINAL PATHOPHYSIOLOGICAL FEATURES  Airflow limitation  Airway hypersensitivity  Airflow limitation

Usually reverses spontanously or with treatment  Airway hyper responsiveness Exaggerated bronchoconstriction to wide variety of non specific stimuli like cold air and exercise

 Airflow limitation  Bronchial smooth muscle hypertrophy  Mucosal edema  Thickening of basement membrane  Inflammatory cells in submucosal tissues : --Oesinophils, lymphocytes,mast cells and neutrophills

CLASSIFICATION Bronchial asthma may be  Allergic or extrinsic  Non allergic or intrinsic

EXTRINSICINTRINSIC Known external allergenNo known external allergen +ve skin test-ve skin test ↑ IgENormal IgE Onset in childhood or early adult life O nset in older adults Intermittant asthmaMore continous other allergens—hay fever and eczema often present Other allergens uncommon Family h/o multiple allergensFamily h/o allergens uncommon Tendency to improve during adolescent Usually progressive disease

PRECIPITATING FACTORS  Allergens  Pollens  Mold  Dust  Cockroaches  Fur of animals  Feathers of birds

 Irritants  air pollution  Tobacco smoke  Perfumes /sprays /deodrants  Strong odors from household chemical like paint detergents like chlorox,insectisides like raid

Other potential triggers  Certain food  Feather pillows  NSAID  Sinus infections  GERD  Temp changes

Classification Classification is based upon the following  Improvement over the previous 2-4 weeks  Current values of FEV1and FVC  Number of exacerbation requiring oral steroids / year

Classification  Intermittant  Persistant  Moderate persistant  Severe persistant

Other classification  Exercise induced asthma  NSAID sensitive asthma  Nocturnal asthma  Adult onset  Occupational---triggered by condition in work place

Clinical features  Usually presents as attacks of wheezing, which commonly occur following exercise and viral infections  Less severe symptoms are nocturnal coughing and wheezing  Some patients present with breathlessness alone

SEVERE ASTHMA Features of severe asthma are—  Inability to speak complete sentence  Exhaustion  Resp rate < than 30 / min  Silent chest—severe bronchospasm prevents air entry  Cyanosis  Tachycardia < than 120 / min  Pulses paradoxus

INVESTIGATIONS  Blood gases  CXR  CBC—increased oesinophils  Spirometry –this demonstrates reversible airflow obstruction.FEV1 / FVC should be done before and after bronchodilator----improvement of %  PFM  Skin testing

FVC Measures the volume of air exhaled over a continous period of 6 seconds—this helps to provide an indication of how much air the lungs can hold FEV1 Measures the speed of air exhaled in one second

Bronchoprovocation testing  inhaled methacholine  Inhaled histamine  Exercise challenge