Occupational asthma
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-In-Chief: Lakshmi Gopalakrishnan, M.B.B.S. [2]
Overview
Historical Perspective
Classification
Pathophysiology
Causes
Differentiating Occupational asthma from other Diseases
Epidemiology and Demographics
Risk Factors
Screening
Natural History, Complications and Prognosis
Diagnosis
Diagnostic Criteria | History and Symptoms | Physical Examination | Laboratory Findings | EKG | Chest X ray | Other Diagnostic Studies
Treatment
Medical Therapy | Surgery | Primary Prevention | Secondary Prevention | Cost-Effectiveness of Therapy | Future or Investigational Therapies
Case Studies
Diagnosis
Skin prick tests
- A skin prick test is performed on the inner aspect of the forearm. A technician will draw a grid and systematically drop specific allergens within grid spaces. The skin is then pricked through a lancet to induce a potential interaction.
- Reactions, if any, occur within 10-15 minutes of allergen contact. The results of these reactions assist in determination of level of severity of allergic reaction and types of allergic triggers.[1]
IgE-specific tests
- Immunoglobulin E is an antibody that is effective against toxins. Since it can also trigger allergic reactions to specific allergens like pollen, the IgE test is performed to evaluate whether the subject is allergic to these substances[2].
Spirometric tests
- Conventionally, a spirometer is a device used to measure timed expired and inspired volumes.
- Expired and inspired volume measurements then enable us to measure how quickly the lungs can be emptied and filled and whether it is effective.
- These measurements need to be stated at body temperature and the pressure will have to be saturated with water vapor to get the correct values. The specificity of measurement is important as if the spirometer is dry, the recorded volume of air displaced is lower than that actually displaced by the lungs[3].
Peak Expiratory Flow at work
- This test uses the peak expiratory flow at rest (PEFR) method. The primary difference from the at-rest test is that at work testing measures the functioning of the patient's airways at his place of work and not necessarily in a controlled environment. The patient breathes into a Peak Expiratory Flow monitor (a hand-held device that has a mouth piece at one end and a scale with an indicator on the other).[4]
Specific inhalation challenge
- Realistic method “The Realistic Method” is a whole body sealed chamber where the patient is exposed to articles that are present in their workplace. This method has the advantage of being able to assess, albeit highly subjectively, ocular and nasal symptoms as well as a reduction in FEV1.
- Closed-circuit method This test requires the patient to breathe aerosols of the suspected ‘asthmagens’ through an oro-facial mask. These ‘asthmagens’ are aerosolized using closed circuit chambers, and the quantities and concentrations administered being minute and extremely stable minimize the risk of exaggerated responses.
- Of the above methods of doing a diagnosis, procedures such as monitoring of spirometry or peak expiratory flow at work and Specific Inhalation Challenges (SIC) have been proved as the most objective and reliable methods.
Treatment
- According to the Canadian Centre for Occupational Health and Safety (CCOHS), better education of workers, management, unions and medical professionals is the key to the prevention of OA. This will enable them to identify the risk factors and put in place preventive measures like masks or exposure limits, etc.
- Recovery is directly dependent on the duration and level of exposure to the causative agent. Depending on the severity of the case, the condition of the patient can improve dramatically during the first year after removal from exposure.
- Three basic types of procedures are used for treating the affected workers[5]:
1) Reducing exposure
- This method is most effective for those affected by irritant-induced OA.
- Thus, by reducing their exposure duration and level to the causative agent, the probability of suffering another reaction is lowered. But exposure can be reduced in other ways like making use of face masks or providing better ventilation.
- Now, more and more di-isocyanate free spray paints are available.
- Similarly, most hospitals and healthcare companies have exchanged latex gloves for other materials. Thus, reducing exposure to known asthmagens can also be used as a preventive measure.
2) Removal from exposure
- Persons affected by OA that occurred after a latency period, whether a few months or years, must be immediately removed from exposure to the causative agent. This is their only chance of recovery.
- This entails severe socio-economic consequences for the worker as well as the employer due to loss of job, unemployment, compensation issues, quasi-permanent medical expenditures, hiring and re-training of new personnel, etc.
- According to recent research, the probability that those who suffer from OA remain unemployed longer than those who suffer from non-occupational asthma is higher. One solution to this problem is relocating the employee in the same company away from the causative agents.
3) Medical and pharmacological treatment
- Anyone diagnosed with asthma will have to undergo medical treatment.
- This is complementary to either removing or reducing the patient’s exposure to the causal agents.
- Two types of medication can be used:
- Relievers or bronchodilators
- Preventers Anti-inflammatory agents like corticosteroids, LKTRA or mast cell stabilizers can be used depending on the severity of the case.
Short-acting beta-agonists like salbutamol or terbutaline or long-acting beta-agonists like salmeterol and formoterol or anticholinergic, etc. dilate airways which relieve the symptoms thus reducing the severity of the reaction. Some patients also use it just before work to avoid a drop in the FEV1.
Compensation issues
- When a person is diagnosed as having occupational asthma, it can result in serious socio-economic consequences not only for the workers but also for the employer and the healthcare system. The employee has to be taken off job immediately to prevent any further damage to his health. And, the probability of being re-employed is lower for those suffering from OA as compared to those suffering from normal asthma. The employer not only pays compensation to the employee, but will also have to spend a considerable amount of time and energy and funds for hiring and training new personnel. [6][7]
Related Chapters
References
- ↑ http://www.ncbi.nlm.nih.gov/sites/entrez?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=9333767 Kroczyńska-Bednarek J, Grzelewska-Rzymowska I, Tymińska K.
- ↑ Allergy Society of South Africa. The Skin Prick Test. Toerien A,Potter P C, Buys C
- ↑ http://researchnews.osu.edu/archive/hayfcare.htm
- ↑ http://www.nationalasthma.org.au/html/management/spiro_book/sp_bk002.asp
- ↑
- ↑ http://www.nlm.nih.gov/medlineplus/ency/article/003443.htm
- ↑ Medicolegal and compensation aspects of occupational asthma. Dewitte JD, Chan-Yeung M, Malo J-L.