Specific inhalation challenge
Encyclopedia
The Specific Inhalation Challenge (SIC) is defined as a diagnosis tool
to assess airway responsiveness to "sensitizing" substances as opposed to
nonspecific stimuli such as pharmacological agents (i.e. histamine, methacholine),
cold air and exercise.
Subjects are exposed to a suspected occupational agent in a controlled way under close supervision
in a hospital laboratory. The specific inhalation challenges has been considered as the
gold standard in confirming the diagnosis of occupational asthma
.
.
Then, FEV1 is subsequently measured using another device and compared to a baseline.
A positive response is usually a decrease in baseline FEV1 of 15 to 20 percent.
The patient enters a sealed chamber and is exposed to the suspected agent in a controlled,
non-work, test environment. The asthmagen can be water-soluble and nebulized.
If the agent is non-soluble, the patient tips the agent from one tray to another in an attempt
to mimic the work environment. This method has the advantage of being able to assess,
albeit highly subjectively, ocular and nasal symptoms as well as a reduction
in FEV1.
There are, however, disadvantages to the method. First, SIC is currently only conducted
in specialty facilities because the facilities and equipment are rare and expensive.
Second, the realistic method may exposed the patient to huge concentrations of particles,
resulting in unduly severe asthma
attacks.
Alternately, the agent can be delivered using the recently developed closed-circuit technique.
through an oro-facial mask or mouth piece.
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.
to assess airway responsiveness to "sensitizing" substances as opposed to
nonspecific stimuli such as pharmacological agents (i.e. histamine, methacholine),
cold air and exercise.
Subjects are exposed to a suspected occupational agent in a controlled way under close supervision
in a hospital laboratory. The specific inhalation challenges has been considered as the
gold standard in confirming the diagnosis of occupational asthma
Occupational asthma
Occupational asthma is an occupational condition defined as: "a disease characterized by variable airflow limitation and/or airway hyper-responsiveness due to causes and conditions attributable to a particular occupational environment and not stimuli encountered outside the workplace".Asthma is...
.
SIC methods
One of the steps of SIC is to perform a challenge with the suspected asthmagenAsthmagen
An asthmagen is any substance that is causally-related to the development of asthma symptoms....
.
Then, FEV1 is subsequently measured using another device and compared to a baseline.
A positive response is usually a decrease in baseline FEV1 of 15 to 20 percent.
Realistic Method
The Realistic Method was developed in the 1970s.The patient enters a sealed chamber and is exposed to the suspected agent in a controlled,
non-work, test environment. The asthmagen can be water-soluble and nebulized.
If the agent is non-soluble, the patient tips the agent from one tray to another in an attempt
to mimic the work environment. This method has the advantage of being able to assess,
albeit highly subjectively, ocular and nasal symptoms as well as a reduction
in FEV1.
There are, however, disadvantages to the method. First, SIC is currently only conducted
in specialty facilities because the facilities and equipment are rare and expensive.
Second, the realistic method may exposed the patient to huge concentrations of particles,
resulting in unduly severe asthma
Asthma
Asthma is the common chronic inflammatory disease of the airways characterized by variable and recurring symptoms, reversible airflow obstruction, and bronchospasm. Symptoms include wheezing, coughing, chest tightness, and shortness of breath...
attacks.
Alternately, the agent can be delivered using the recently developed closed-circuit technique.
Closed-Circuit Method
This test requires the patient to breathe aerosols of the suspected agent (asthmagen)through an oro-facial mask or mouth piece.
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.
External links
- SCL Medtech - For any questions on workplace asthma diagnosis, especially Specific Inhalation Challenge
- Occupational Asthma (UK) - Created by some of the most important people in the field, in UK. For any questions/ help on Workplace asthma