Occupational Asthma Occupational Asthma

Dr.Pourabdian MDDr.Pourabdian MD

Diseases associated with occupational Diseases associated with occupational exposureexposure

Clinical manifestations of lung diseases are the same Clinical manifestations of lung diseases are the same irrespective of the etiologyirrespective of the etiology

Airway diseasesAirway diseases

Asthma (reversible)Asthma (reversible) Chronic obstructive lung disease (irreversible)Chronic obstructive lung disease (irreversible)

CancerCancerParenchymal diseasesParenchymal diseases

Hypersensitivity pneumonitis (reversible)Hypersensitivity pneumonitis (reversible) Diffuse fibrosis (irreversible)Diffuse fibrosis (irreversible) eg. silicosis, asbestosiseg. silicosis, asbestosis

% occupational asthma in % occupational asthma in occupational lung diseasesoccupational lung diseases

UK BC, CanadaUK BC, Canada

(1989)(1989) (1992)(1992)

AsthmaAsthma 26.4 26.4 52.0 52.0

Pneumoconiosis Pneumoconiosis 15.4 15.4 17.8 17.8

OthersOthers 58.2 58.2 30.2 30.2

Symptoms:

*Coughing

*Tight feeling in the chest

*Shortness of breath

*Wheezing

Recognise and establish work-Recognise and establish work-

relatednessrelatedness

• Aware and suspectAware and suspect

• Occupational historyOccupational history

• Medical history suggesting work-relatednessMedical history suggesting work-relatedness– Symptoms started after employmentSymptoms started after employment– Improvement of symptoms during weekends and Improvement of symptoms during weekends and

holidaysholidays– Worsening of symptoms on returning to workWorsening of symptoms on returning to work

• Objective testingObjective testing

Presentation of Occ AsthmaPresentation of Occ Asthma

• Immediate hypersensitivity reactionImmediate hypersensitivity reaction

• Immediate bronchospasmImmediate bronchospasm

• Isolated late response (usually sensitizer-Isolated late response (usually sensitizer-induced)induced)

• Sleep disorderSleep disorder

• Variable/dual response Variable/dual response

Types of Occupational AsthmaTypes of Occupational Asthma

• New OnsetNew Onset

- Sensitizer-induced- Sensitizer-induced

- Irritant induced- Irritant induced• Aggravation of underlying asthmaAggravation of underlying asthma• Reactive airways dysfunction syndrome (RADS)Reactive airways dysfunction syndrome (RADS)• Cold air- or exercise-induced syndromeCold air- or exercise-induced syndrome• Airways reactivity secondary to hypersensitivity Airways reactivity secondary to hypersensitivity

pneumonitispneumonitis

Work-related asthma(WRA)

Occupational asthma, caused by work

(OA)

Work-exacerbated asthma (WEA)

Sensitizer-induced OAIrritant-induced OA(Including reactive airways

dysfunction syndrome, RADS)

Chest 2008

Occupational Asthma Occupational Asthma

Sensitizer-inducedSensitizer-induced

• Specific antigen Specific antigen

• Minimal exposureMinimal exposure

• Stereotyped response Stereotyped response

• PPE often insufficient to PPE often insufficient to control symptomscontrol symptoms

• Medical removal usually Medical removal usually necessary necessary

Irritant-inducedIrritant-induced

• Any irritant Any irritant

• Moderate to heavy Moderate to heavy exposureexposure

• Often variableOften variable

• PPE often effective in PPE often effective in preventing episodespreventing episodes

• Medical removal the last Medical removal the last resort resort

Sensitizer-Induced Occ AsthmaSensitizer-Induced Occ Asthma

• Sensitization to a specific antigenSensitization to a specific antigen - low molecular-weight, “hapten”- low molecular-weight, “hapten” - high molecular weight- high molecular weight• Reaginic Ab, mostly IgE, mediatedReaginic Ab, mostly IgE, mediated• Presentation variablePresentation variable - late phase reactivity- late phase reactivity - immediate sensitivity- immediate sensitivity - dual or variable responsiveness - dual or variable responsiveness

Thuja plicataWestern red cedar

Exposure to nickel dust

Spirometry • at and away from work• cross-shift

Exposure challenge testing

Sensitizer-Induced Asthma 2Sensitizer-Induced Asthma 2

• Sensitization may occur at <OELSensitization may occur at <OEL• Sensitizers may also be irritants (e.g. Sensitizers may also be irritants (e.g.

TDI,TMA)TDI,TMA)• Prior history of atopy predict risk of asthma Prior history of atopy predict risk of asthma • Therefore no basis of exclusion of persons Therefore no basis of exclusion of persons

with allergies from workplace with allergies from workplace

Common SensitizersCommon Sensitizers(Incomplete List!)(Incomplete List!)

Low MW Low MW

• IsocyanatesIsocyanates

• AnhydridesAnhydrides

• Metal saltsMetal salts

• Epoxy resinsEpoxy resins

• FluxesFluxes

• PersulfatePersulfate

• Aldehydes Aldehydes

High MWHigh MW

• Pharmaceuticals Pharmaceuticals

• Animal proteinsAnimal proteins

• LatexLatex

• CerealsCereals

• SeafoodSeafood

• Proteolytic enzymesProteolytic enzymes

• Wood constituents Wood constituents

Irritant-Induced Occupational Irritant-Induced Occupational AsthmaAsthma

• More common, clinically, than sensitizer-inducedMore common, clinically, than sensitizer-induced• Often represents clinical expression of airways Often represents clinical expression of airways

hyperactivity + irritant exposurehyperactivity + irritant exposure• May be induced by any irritating exposureMay be induced by any irritating exposure• Usually history of intolerance to second-hand Usually history of intolerance to second-hand

tobacco smoke tobacco smoke • Some irritant exposures may also be sensitizing: Some irritant exposures may also be sensitizing:

CHO, TDI,TMA CHO, TDI,TMA • Classic example is “hot wire” asthmaClassic example is “hot wire” asthma

RADSRADS

• Acute onset following exposure to irritantAcute onset following exposure to irritant• Generally exposure of moderate severityGenerally exposure of moderate severity• Prognosis good but may have several years of Prognosis good but may have several years of

airway hyperactivity and sequelae airway hyperactivity and sequelae • Often associated with: Often associated with:

– upper airway problemsupper airway problems– sleep disordersleep disorder

• Independent of prior history of airways reactivityIndependent of prior history of airways reactivity• Conventional managementConventional management

Aggravational AsthmaAggravational Asthma• Very commonVery common

• Existing airways reactivity: Existing airways reactivity: – asthmaasthma– hay fever and rhinitishay fever and rhinitis– other airways disease (e.g. COPD)other airways disease (e.g. COPD)

• Initial condition not occupationalInitial condition not occupational

• Moderate irritant exposure Moderate irritant exposure

• Provokes airways responseProvokes airways response

• Usually self-limitedUsually self-limited

Exposure chamber

Typical patterns of responseTypical patterns of response

Monitoring of PEFMonitoring of PEF - - How to do it ?How to do it ?• At least At least 2 weeks at work and off work2 weeks at work and off work

(often longer...)(often longer...)• At least 4 times daily, preferably every 2 hoursAt least 4 times daily, preferably every 2 hours• Medication allowed: Medication allowed:

keep constant & at minimum dose...keep constant & at minimum dose... beta-2 agonist on demand onlybeta-2 agonist on demand only continue inhaled steroids/theophyllinecontinue inhaled steroids/theophylline avoid, if possible, long-acting beta-2-agonist avoid, if possible, long-acting beta-2-agonist

Patterns of Airways ResponsePatterns of Airways Response

Immediate Late Repetitive Interstitial

Onset 10-20 m 4-6 h Periodic 4-6 h

Duration 1-2 h 2-6 h Days 4-12 h

Abnorm-ality

FEV1 FEV1

FEV1 FVC

Immunity IgE IgE or IgG ? IgG + cell

Symptoms Wheezing Wheezing,sob

Wheezing,recurrent

Sob, fever,chills,

Therapy bd bd, anti-inflamm

bd anti-inflamm

Immediate responseImmediate response

• Same shift, rapid onsetSame shift, rapid onset• Reaginic antibody if sensitizer-inducedReaginic antibody if sensitizer-induced• Acute mediatorsAcute mediators• Responds to conventional asthma RxResponds to conventional asthma Rx• Often difficult to distinguish from conventional Often difficult to distinguish from conventional

asthma asthma • Irritant-induced tends to be milderIrritant-induced tends to be milder

Late RespondersLate Responders

• Onset of bronchospasm hours after exposureOnset of bronchospasm hours after exposure• Usually wheezing post-shiftUsually wheezing post-shift• Often presents as a sleep disorderOften presents as a sleep disorder• If isolated, usually associated with certain antigens If isolated, usually associated with certain antigens

(Western red cedar, TDI)(Western red cedar, TDI)• Often combined Often combined

Dual/Variable effectsDual/Variable effects

• Dual responders may combine immediate + late Dual responders may combine immediate + late responsesresponses

• Variations may include cyclic bronchospasm (esp. Variations may include cyclic bronchospasm (esp. Western red cedar)Western red cedar)

• May be prolonged, sustained response (TDI, May be prolonged, sustained response (TDI, byssinosis)byssinosis)

• Usually slow recovery, relatively refractory to Usually slow recovery, relatively refractory to conventional Rx conventional Rx

Special CasesSpecial Cases

The following subsets of occupational asthma The following subsets of occupational asthma have special features:have special features:

• Laboratory animal sensitivity (high risk of Laboratory animal sensitivity (high risk of anaphylaxis)anaphylaxis)

• Cotton dust, byssinosisCotton dust, byssinosis

• Grain dust Grain dust

• Hypersensitivity pneumonitis may have an Hypersensitivity pneumonitis may have an airways componentairways component

Cold Air / Exercise-Induced AsthmaCold Air / Exercise-Induced Asthma• May be associated with: May be associated with:

– dry cold airdry cold air– exertionexertion– hyperventilationhyperventilation

• Work in cold, dry climatesWork in cold, dry climates• Immediate response, short durationImmediate response, short duration• Further exercise may improve airflow! Further exercise may improve airflow! • Mechanism: airway drying and coolingMechanism: airway drying and cooling

– stimulates vagal receptorsstimulates vagal receptors– histamine, mediator release from mast cellshistamine, mediator release from mast cells

Principles of Evaluation Principles of Evaluation

• Demonstrate airways reactivityDemonstrate airways reactivity

- History- History

- Presence of wheezing- Presence of wheezing• SpirometrySpirometry• Methacholine challengeMethacholine challenge• Bronchoprovocation or substituteBronchoprovocation or substitute

- Symptom diary- Symptom diary

- Pre/post shift - Pre/post shift

Methacholine ChallengeMethacholine Challenge

• + Test confirms airways reactivity only + Test confirms airways reactivity only • A functional test not specific for asthmaA functional test not specific for asthma - atopy- atopy - transient reactivity - transient reactivity • Bronchoprovocation with with specific antigen Bronchoprovocation with with specific antigen

preferable to diagnose sensitizer-induced asthmapreferable to diagnose sensitizer-induced asthma• -Tests can occur with quiescent occ asthma -Tests can occur with quiescent occ asthma

Risks of Bronchoprovocation Risks of Bronchoprovocation

• AnaphylaxisAnaphylaxis

• Iatrogenic reaction Iatrogenic reaction

• SensitizationSensitization

Ancillary TestsAncillary Tests

• Clinical immunologyClinical immunology

- skin prick tests- skin prick tests

- RAST- RAST

- ELISA- ELISA

• PEF or FEVPEF or FEV11, symptom and medication diary , symptom and medication diary

• Pre/post shift and/or holiday PFTsPre/post shift and/or holiday PFTs• Work place HHE Work place HHE

Management Management

• Conventional Rx for asthmaConventional Rx for asthma• Medical removal – consider optionsMedical removal – consider options• Physician’s First Report Physician’s First Report • Impairment Assessment (c.f. Impairment Assessment (c.f. AMA AMA

guidelinesguidelines))• Avoid irritantsAvoid irritants• Evaluate PPE Evaluate PPE

Compensation Management Compensation Management

• Document causationDocument causation• Document impairment (episodic?)Document impairment (episodic?)• Medical removal required?Medical removal required?• Claimant factorsClaimant factors

- degree of impairment - degree of impairment

- age- age

- retraining - retraining

Impairment – Disability Impairment – Disability

Pop Health Management Pop Health Management

• Treat as “Sentinel event”Treat as “Sentinel event”

• SurveillanceSurveillance

• Identification of specific hazard when Identification of specific hazard when possiblepossible

• Hazard ControlHazard Control

- engineering controls- engineering controls

- PPE - PPE