Dept of Community Medicine

Asthma and its Prevention

Quick Overview (1)

• Asthma – What is it?• Symptoms of asthma• What is work-related asthma?• How common is asthma (work and non work related)?• What is the pathophysiology of asthma?• How asthma is treated?• Clues that suggest asthma may be work-related• What YOU can do if you have asthma• What is the take-home Public Health message

regarding asthma?

• What is the Epidemiology of asthma?• What is the Prevalence of asthma• What is the Etiology of asthma?• What is the Etiological classification asthma)?• What is the Etiological classification asthma (by

allergens)• How is asthma treated?• What is the take-home Public Health message

regarding asthma?• What substances trigger asthma?• What are the problems of poorly controlled asthma?

Quick Overview (2)

• Clues that suggest asthma may be work-related• What YOU can do if you have asthma• What are the diagnostic and lung function tests?• Case presentation in young (non occupational

asthma)• Acute severe asthma and status ashmaticus• Case in older (example of Occupational asthma)

Quick Overview (3)

Asthma – What is It? (1)• Asthma is a chronic lung

disease with recurrent, obstruct-ion of airflow particularly at particularly at night and early morningnight and early morning

• The obstruction is reversible either spontaneously or either spontaneously or with therapywith therapy

• It involves difficulty in breathing due to

– A-Inflammation (swelling)

– B- Mucus in the airways (hypersecretion)

– C-Tightening of muscles around airways (hyperconstriction)

Airway fill with mucus

Muscles contract

Airways swell

“B” and “C” is called Bronchial hyperresponsiveness

Asthma – What is It? (2)

1. Acute bronchoconstriction1. Acute bronchoconstriction2. Swelling of the airway wall2. Swelling of the airway wall3. Chronic mucus plug formation4. Airway wall remodeling

Relaxation Constriction

Normal

Asthma

Airway narrowing

Exaggeratedairway narrowing

muscle constriction

muscle constriction

Asthma – What is It? (3)

–1 type hypersensitivity reaction.

–The genesis of any allergic reaction may be divided into

–immune, pathochemical and pathophysio-logic phases.

What is the pathophysiology of asthma?

Immune phase (1)

• Allergens activate immunocompetent cells.

• As a result B-lymphocytes produce antibodies of Ig E class.

• T-lymphocytes are inhibited, so the • activation of B-lympocytes and Ig E production

are excessive, exceeding normal needs.

B-cell

Allergens

T-cell

Allergen-specificIgE

• Antibodies bind to the surface of mast cells, basophils and eosinophils.

• And cause release of cell contents (this leads to reaction)

This is a first, immune phase of allergic reaction.

Immune phase (2)Mast cells and eosinophils and basophils

Pathochemical phaseAs a result of antigen-antibody reaction the peculiar

“explosion” occurs. The membranes of mast cells, basophils and eosinophils break open with output of biologically active substances (histamine, serotonin,etc),

which induce

•inflammation,

•mucous edema,

•spasm of smooth muscle,

•glands hypersecretion

Airway fill with mucus

Muscles

contract

Airways swell

What are microscopic changes of chronic asthma (1)?

• Bronchial wall infiltration with mast cells, eosinophils, basophils and T-lymphocytes

• Edema of mucous and submucous tunics

• Destruction of bronchial epithelium

• Hypertrophy of bronchial smooth muscles,

• Hyperplasty of submucous glands

• Microvessels dilation

What are Microscopic changes in chronic asthma ? (2)

Normal airway

Airway wall remodeling Epithelium

Basement membrane

Smooth muscle

Mucus plug

Mucus glands

Charcot-Leyden

Crystals

Needle shaped crystals -

Represents breakdown products of eosinophils

Important microscopic finding (both acue or chronic)

What are Microscopic changes in chronic asthma ? (3)

Symptoms of asthma

• Coughing

• Wheezing, a whistling sound

• Shortness of breath

• Chest tightness

• Sneezing & runny nose (why?)

• Itchy and inflamed eyes (why?)

What is work-related asthma?

• Pre-existing asthma that is triggered or made worse by exposure to one or more substances in the work-environment

OR

• Asthma that is caused by exposure to substances in the work-environment

• Signs and symptoms are the same for asthma and work-related asthma

What is the Epidemiology of asthma? According to epidemiological studies asthma affects 1-

18% of population of different countries. Only in 2006 more than 300 million patients

suffered from asthma all over the world, 250 thousands of patients die of asthma. The incidence of asthma is higher in countries with increased air pollution.

• Up to 20% of all adult asthma cases maybe work-related asthma

• Of those diagnosed with work-related asthma:– 20-27% are individuals with pre-existing asthma who react to substances

in the workplace– Up to 80% develop asthma due to work-place exposures

What is the Prevalence of asthma?

• Estimated prevalence worldwide– 10 – 15%

• Most asthmatics have mild to moderate disease, with severe asthma thought to affect less than 10% of asthmatics.

• More common in males ( but equal after age of 20)

What is the Etiology of asthma?• Extrinsic asthma

– Allergic or atopic asthma (Skin test reactivity, elevated IgE levels, blood eosinophilia.(some genetic predisposition); indoor allergens

• Intrinsic asthma– Nonallergic or nonatopic asthma ; Environmental

pollution, occupational exposure

A. Intr insic asthma• no environmental causes can be identified• negative skin test to common airborn allergens• rather negative family history • (no lab findings of mast cells, eosinophils etc)

B. Extrinsic asthma• atopy, genetic predisposition∀ ↑ IgE, mast cells and eosinophils response to allergens• (lab findings of mast cells, eosinophils etc)C. Occupational asthma• sensibilisation of airways to inhalant chemicals

What is the Etiology classification of of asthma?

EarlyIntervention

2o

Prevention

1o

Prevention

ASTHMA

Airways Injury

• Viral infections• Aeroallergens• Pollutants/toxicants

AberrantRepair

• Persistent inflammation• Tissue remodeling• Lung growth/differentiation

Age

Biological & Genetic Risk• Immune• Lung• Repair

Environment• Allergens• Microbes• Pollutants• Stress

Aberrant immune development & response

Atopy

Asthma Prevention

The allergens are divided into:

•communal •industrial •occupational•natural •pharmacological

What is the Etiology classification of of asthma? (Another type by

allergens)

Asthma Classification Based on Severity

Disease Symptoms

Step 4: Continual symptoms

Step 3: Daily symptoms

Step 2: Symptoms > than twice weekly

Step 1: Symptoms < than twice weekly

What substances trigger asthma?

Type of Substance ExamplesAir pollutants, including dusts, smoke, mists & fumes

Diesel exhaust; tobacco smoke; mineral, rock, coal, & wood dusts; gases; fumes & vapors from aerosol agents, chemicals, cleaning materials, solvents, paints, welding & from heating & cooling metals quickly

Pollens, mites & molds Trees, flowers, weeds, hay, plants

Animal dander Birds, cats, dogs

Medications Aspirin, anti-inflammatory drugs

Foods Egg, wheat, nuts

How is asthma treated (1)?

• Asthma can be controlled (but not cured) by:– Avoiding triggers or reducing exposure to triggers

– Using medication to control symptoms

• Medications - generally two types are used – Controller or long-term drugs

• Taken to prevent excess production of mucus & to reduce the inflammation and constriction of airway muscles

– Rescue or quick-relief drugs• Taken to relax muscles around the airways to improve

breathing

How is asthma treated (2)

• Repeated doses of short acting B2 agonist – driven by oxygen– repeated doses every 15 – 30 min

• Systemic corticosteroids– The earlier they are administered the better

the outcome

• Oxygen

Medications to Treat Asthma: How to Use a Spray Inhaler

The health-care provider should evaluate inhaler technique at each visit.

Source: “What You and Your Family Can Do About Asthma” by the Global Initiative for Asthma Created and funded by NIH/NHLBI

Drug therapy

Antiinflammatory drugs(basic) Bronchodilators

2 drug categories are used:

Are divided into:

hormone-containing (corticosteroids)

nonhormone-containing (less common) (cromones, leukotriene receptor antagonists)

3 groups:

anticholinergic drugs

β2-agonists

Methylxanthines (less common)

Bronchodilators

β2-agonists Anticholinergic drugs

Smooth muscle relaxation

Stimulates β2-adrenergic receptors of bronchi

reduce tonus of vagus

What are the problems of poorly controlled asthma?:

• Increased visits to – Doctor, Urgent Care

Clinic or Hospital ER

• Hospitalizations• Limitations in daily

activities• Lost work days• Lower quality of life• Death

> 50% OF THE COMPLICATIONS IN ASTHMATIC PATIENTS BEING VENTILATED OCCUR DURING OR IMMEDIATELY AFTER INTUBATION

What clues suggest that asthma is work-related?

• Do symptoms:– Occur only at work or

regularly after a work-shift?

– Improve on weekends or vacations?

– Increase over the course of the work week?

– Improve after changes in the work environment?

Information to share with doctor

• Discuss your symptoms.– When do they occur?

– How often do they occur?

– Time of day or week that symptoms are worse

– Times you feel better– Identify

• Substances in the work-place to which you are exposed

• Current and previous jobs, hobbies, and smoking habits that may affect your lungs

What YOU can do if you have asthma?

• Identify and minimize contact with your asthma trigger(s)

• Understand and take asthma medications as prescribed

• Recognize early signs that your asthma is getting worse

• Know what to do when your asthma is getting worse

What is the take-home public health message regarding asthma?

Key Messages

• Asthma is an inflammatory disease in which Environmental factors are (a) important and (b) many types

• Health education is crucial (Awareness)

• Emphasis on recognition and avoidance of triggers (Prevention)

Diagnostic Tests

• No single test can secure a diagnosis of asthma

• Spirometry is the most helpful, preferred method for establishing diagnosis.– Many asthma patients are negative and

repeat testing is advised.

Lung function assessmentThe diagnosis and severity assessment of

asthma is based mainly on parameters of lung function. The most important of them are:

forced expiratory volume in 1 second (FEV1) and peak expiratory flow (PEF), which

are measured during spirometry at forced breathing-out.

Case presentation (non occupational)

• 2 year old boy• Presents with tight chest and wheezing• No previous episodes• No TB contact• No allergies• No important previous medical history• Cyanotic (blueness in face)• No clubbing (this is change in shape of finger

tips; it happens because of heart or lung problems)

• Severely distress

Respiratory system (young)

• Tachypnea (fast breathing; more than 20 breaths in adults but this maybe normal for children; in 2 year boy more than 26 breaths or so)

• Retraction of ribs

• Both are considered key signs asthma

• Also, hyperresonant on percussion

Chest X-ray reveals:

• hyperlucency of lung fields

• low standing and limited mobility of diaphragm

• expanded intercostal spaces

• horizontal rib position.

What define a severe acute attack?

• Disturbance in level of consciousness• Inability to speak and/or feed• Severely diminished or absent breath sounds• Central cyanosis (cyanosis around lips).• Use of accessory muscles while breathing.• Increased respiratory and cardiac rate

What define a Status asthmatics

“Defined as wheezing which does not respond to initial treatment with inhaled bronchodilators “

Additional points

• Sudden onsets

• Failure of the long-term management plan.

• Acute severe asthma is one of the most common medical emergency situations in childhood

The examination of working capacity (part of occupational

health)

– The patients with unfavorable condition for the disease, need the job replacement.

Case presentation 2 ( occupational)

Exposure to nickel dust

and occupational asthma

Risk classification of developing an occupational asthma

Risk History Risk Comments

NormalNo evidence of allergic disease ~10%

Minimal risk even upon repeated exposure

AtopicPre-existing allergic disease

Up to 73%Risk increases with repeated exposure

AsymptomaticIgE antibodies to allergenic proteins

Up to 100%

Risk of developing symptoms increases with repeated exposure

Symptomatic

Clinical symptoms on exposure to allergenic proteins

100%

33% with chest symptoms; 10% may develop occupational asthma; minimal exposure may lead to permanent impairment

Bonus Questions

Q) What are biopsy and non-biopsy findings of asthma?

Q) What is the most common cause of transient asthma in children in

Pakistan? (with microscopic findings like asthma)

Charcot-Leyden crystals are non-biopsy findings

Parasitic infestations in the GIT cause symptoms like asthma (with Charcot Leyden crystal formation).

Hook worm infection IS most common cause

Answers

Thankyou