Reactive airways dysfunction syndrome (RADS) is defined as the sudden onset of asthma like symptoms following a high level irritant gas, vapor, or fume exposure. It was originally described by Doctors Brooks, Weiss, and Bernstein in an article in the journal Chest in 1985 (Chest 1985; 88:376-84).
Patients with RADS present with symptoms of shortness of breath, wheeze and cough within 24 hours of an exposure to a high level of respirable irritant. The exposure is typically single, high level and brief. Patients present appearing extremely ill with signs of toxicity, including conjunctival and mucous membrane erythema and edema with labored breathing.
Patients respond to supportive therapy, including bronchodilators, intravenous steroids, and intravenous crystalloid for volume resuscitation where indicated. Some patients are left with permanent airway hyperresponsiveness. Some recover fully after a number of months.
A second type of irritant induced asthma-not so sudden induced asthma-has been described by a number of investigators but most notably by Dr. Brooks and colleagues in an article appearing in the journal Chest (Chest 1998; 111:42-49). These patients are exposed to a low level of respirable irritant for more prolonged periods of time. The exposure is generally of a more chronic nature. Symptoms of airway hyperresponsiveness take longer to develop in these patients. Their presentation is one of dyspnea, wheezing, and sometimes chronic cough. They do not appear as acutely ill as patients with sudden onset irritant induced asthma. Dr. Brooks and colleagues have found patients with not so sudden induced asthma have a high prevalence of atopy, with 52% of the patients in their study in the aforementioned journal having a history of atopy. We feel that patients in this group often have pre-existing host susceptibility. They may have undiagnosed asthma or atopy or other airway dysfunction. These patients also respond favorably to inhaled bronchodilators, inhaled steroids, and other supportive measures. Their symptoms tend to be more protracted and they may require lifelong treatment.