Occupational Asthma Flashcards
(14 cards)
what is AO?
- Is an etiological form of asthma
- asthma that is caused specifically by exposure to an agent present only at the work place not to stimuli outside the workplace
- by substances that are found in work place air
what is the characteristics of OA?
variable airflow limitation and or airway hyperresponsiveness
What is the classification of AO?
- Alergic occupation asthma caused by immunological mechanism - produced by allergen compounds, with OA latency period
- Irritative OA not caused by immunological sensitisation: determined by irritant compounds
diagnostic in AO
- Confirm of asthma diagnosis
- confirmation of pccupational diagnostic
- identification of cause
confirmation of asthma diagnosis
- History (symptoms)
- clincial examen
- spirometry
etiology of allergic occupational asthma
- high molecular weight agents
- low molecular weight agents
HMW agents
- macromolecules of biological origin
- over 300 substances
- classificed into
- animal derived
- plant dervied
- microbe dervived
LMW agents
chemicals < 2500 dalton ‘:
- synthetic
- metallic
- natural chemicals (wood)
- **do not act on IgE **
- act on haptene and/or irritative mechanism
what are haptenes
incompelete antigens that are thought to combine with endogenous proteins to form compelete antigens
OA caused by irritation
name = irritant induced asthma
produced by irritant compounds:
- RADs
- chronic form of irritant asthma
Diagnosis characteristics of RADs (reactive airways dysfunction syndrome)
- occurs from exposure to gas, fumes smoke
- onset of asthma syndrome wintin 24h
- persistence at least 12 weeks
- no symptoms before exposure
- objective evidence airflow limitation with significant bronchodilator responsiveness at least 12% increase in FEV1
- if there is no airflow limitation - BC test is mandatory with histamine/methacholine
history of AO
any P with one or more symptoms of:
- episodic cough
- wheezing
- retrosternal chest thightness
- expiratory dyspnea
symptoms began during working
when increased at work. gone at home
confirmation of asthma by spirtometry
During an asthma attack: Obstructive dysfunction reversible after bronchodilator administration.
Between attacks/after exposure:
Obstructive dysfunction with positive bronchodilator test.
Normal values require non-specific challenge testing (methacholine, histamine, or acetylcholine). Positive test = 15-20% reduction in FEV1.
Distal obstructive dysfunction (decrease in MEF50).
occupational hystory
- occur at work
- or hours after exposure
- improve when at home or off work
- affected fellow workers
