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Asthma

Prevalence of Asthma

Asthma affects 300 million adults and children worldwide Estimated prevalence of asthma is increasing 50% per decade WHO: 15-20 million asthmatics in India Children: 12% and Adults 5%

Parts of the Respiratory System

The microscopic structure of the airways The airways from the windpipe down to the smallest air passages that supply the air sacs, have a similar microscopic structureGoblet cell Ciliated columnar epithelium

Basement membrane Spongy layer Blood cell Smooth muscle layer

Bronchial gland

Classification of the nervous systemNervous system Peripheral Somatic Autonomic Central

Sympathetic

Parasympathetic

Sympathetic receptorsAlpha-E E1 E2 F1 Beta-F F2 Lungs

Where are beta receptors located?Location Effects Smooth muscle cells Relaxation Mast cells Eosinophils Anti-inflammatory Lymphocytes Nerve endings Mucus enhancement Epithelial cells

Parasympathetic receptorsMuscarinic - M M1, M2, M3 Smooth muscle mucus glands Ciliary epithelium Blood vessels Bronchoconstriction o Mucus secretions q Ciliary activity Dilation Oedema

Inflammatory Cellses l

R Bs

W Bs

Ptets lale

Gnloys r ucte a

Aaucte gnloys r

oioh s pils

etrpils uoh

Boh -> atcls apils- M e s s

Lmoys yp cte h Te & cls cls Be

MoysMrpae o cte- aohgs n c

Asthma - DefinitionAsthma is a Chronic inflammatory disease characterized by Airway hyperesponsiveness to a variety of stimuli resulting in Bronchospasm which reverses spontaneously - on treatment

Basic Cellular MechanismsFIRST EXPOSURE Sensitisation process SECOND EXPOSURE Early allergic reaction Late allergic reaction

1st exposure

Allergic ResponseAllergen

oEnters t e o

pro uces IgE anti o ies

SENSITIZATIO N PH ASE

An ti o ies + Allergens

Y

Y

Y

Y

Y

Sensitization

ast cellY

Y

Excess anti o ies in to mast cells

Y

YY

Pro uce In lammator me iators ( istamine) (not release )

Y

Y

Allergic Response2nd exposureI E ti yA er e

Chemotactic Factors

Histamine

5-30 minutes a ter exposure

RLY LL R IC R ( R)

Allergic Response2nd exposureChe otactic FactorsMigration & Activation

Basophils

EOSINOPHILS

Neutrophils

Secondary Mediators

ECP ; MBP

Da age to Epithelial cells (this exposes the parasy pathetic nerves)

INFLAMMA I N Bronchoconstriction Mucus production Ciliary acti ity VasodilationL LL R IC R (L R)

R DN

, W LLINGbetween 3-11 hours a ter exposure

}

Bronchospasm

Histamine Leukotrienes

Acetylcholine

Effects of inflammation in the air aysAirway remodelling: the structural changes in the airways chronic untreated inflammation leads to irreversible changes in the structure of airways.

Fibrosis: Formation of fibrous tissue (destruction of lung tissue) Goblet cell hyperplasia: Increase in the number of goblet cells Neovascularization: Formation of new blood vessels Smooth muscle cell hypertrophy: Increase in the size of smooth muscle cells Basement Membrane Thickening Bronchial Gland Hyperplasia: Increase in the cells of bronchial gland

Acute Effects Bronchoconstriction Plasma leakage Vasodilation Mucus secretion Nerve activation Chronic Effects (Airway remodelling) Fibrosis Smooth muscle cell hypertrophy oblet cell hyperplasia New blood vessel formation

Nocturnal AsthmaNighttime symptoms of wheezing, cough, breathlessness is known as nocturnal asthma.Asthma attacks often occur between 2 and 4 am

70% ofdeaths due to asthma occur at night

Nocturnal AsthmaCauses of Nocturnal Asthma

Exposure to dust mite, animal dander astro-oesophageal reflux Post nasal drip Decreased cortisol levels Increased parasympathetic activity Increased sensitivity to histamine

Diagnosing Asthma

Medical history Physical examination Measurements of lung function Trial use of asthma medications

Peak Flo Meter

Diagnose asthma To determine effectiveness of therapy Identify factors which worsen asthma Warn of an impending attack

Interpretation of PEFR

15-20% increase in the peak flow when measured after administering a bronchodilator, it indicates a significant degree of reversible airflow obstruction.

Diurnal variability of >20% is indicative of Asthma.

SpirometryPatient blows into spirometer. The device measures and records maximum air flow, lung volume, and other parameters which are important in understanding the individuals pulmonary (lung) function

FEV1

The spirometer mainly measures the FEV1 i.e. the volume of air that a person can exhale out forcefully in the first second. The FEV1 values are reduced in case of asthmatics enerally in mild cases it is 1 time a week but < 1 time a day Continuous Limited physical activity Daily Attacks affect activity Frequent Nocturnal Symptoms FEV1 or PEFe 60% predicted

Variability > 30% 60 - 80% predicted

> 1 time week

Variability > 30%

> 2 times a month

u 80% predicted

Variability 20 - 30%

< 1 time a week STEP 1 Intermittent Asymptomatic and normal PEF between attackse 2 times a month u 80% predicted

Variability < 20%

The presence of one feature of severity is sufficient to place patient in that category.

Goals of Asthma Therapy

Minimal (ideally no) chronic symptoms Minimal (infrequent) exacerbations No emergency visits Minimal (ideally no) need for as needed use of 2-agonist No limitations on activities, including exercise PEF circadian variation of less than 20 percent (Near) normal PEF Minimal (or no) adverse effects from medicine

Stepwise Approach to Asthma Therapy - AdultsOutcome: Asthma ControlOutcome: Best Possible Results

Preventer:

Preventer: Preventer: Preventer:None Daily inhaled corticosteroid

Daily inhaled corticosteroid Daily long-acting inhaled 2-agonist

Daily inhaled corticosteroid Daily long acting inhaled 2-agonist plus (if needed)

When asthma is controlled, reduce therapy Monitor

-Theophylline-SR -Anti-Leukotriene -Long-acting inhaled 2- agonist -Oral corticosteroid

Reliever:STEP 1: Intermittent

Rapid-acting inhaledSTEP 2: Mild Persistent

2-agonist

prnSTEP 4: Severe Persistent STEP Down

STEP 3: Moderate Persistent

Alternative controller and reliever medications may be considered