Reactive airways dysfunction syndro...

Reactive airways dysfunction syndrome has been described through Brooks et al[1] as an asthma-like illness following a single prospect to high levels of an irritating vapor, vapors or smoke. Similar symptoms with obstruction of the airways were previously described in several case reports after high-dose aspect to irritants,[2-10] although in about reports, bronchiolitis obliterans may have caused the obstruction of the airways.[11] More newly Boulet[12] has also described a persistent increase in bronchial responsiveness following acute aspect to respiratory irritants. His findings allude to that when an irritant can also cause nonirritant asthma in depressed doses (eg, isocyanates), the patient may become specifically sensitized to it by way of the high-dose exposure. The instant study undertook to determine the prevalence of irritant-induced asthma in patients being assessed for possible occupational disease of the airways and to compare patients having irritant-induced asthma with those having occupational asthma appropriate to known sensitizers.

MATERIALS AND METHODS

A retrospective review was performed onward the files of 154 consecutive workers referr for assessment of possible occupational asthma. They were all seen in the clinics of the Gage Research Institute (35 workers) and the Toronto General Hospital (119 workers) between 1978 and 1987 through one of us (S.M.T.) using the same diagnostic approach throughout

A well stocked [i]or[/i] provided history in all subjects included occupational exposing information on any known spills or unusually high in all sensess respiratory symptoms, date of first brunt and temporal relationship to the workplace. Smoking history, upper respiratory symptoms, history of respiratory symptoms, and family history of allergy were also included, and a sated physical examination was performed.

Skin testing was done on the prick method using a clump of 16 common allergenic extracts (Bencard) and diluent in all patients. Additional skin proofs were performed with known allergens or potential allergens current in the individual's workplace. A positive skin standard was taken as a weal 2 mm or more larger in diameter than that of the govern response, with a surrounding flare.

Baseline pulmonary function exhibitions were performed in all patients at the initial visit, consisting of spirometry, pulmonary books and diffusing capacity. Challenge testing with methacholine inhalation was done using the way described by Juniper and colleagues.[13] A methacholine [PCsub20] of 8 mg/ml or les was taken to indicate bronchial hyperresponsiveness.

Where possible, methacholine challenges were repeated within 48 hours after a day at work and after 10 to 14 days opposite to work. A shift in methacholine [PCsub20] more than fourfold was considered significant in the absence of any confounding factors similar as respiratory tract infections. If the baseline [FEVsub1] was 50 percent of predicted or les or 1 L or les or if the [FEVsub1]/VC ratio was 50 percent or les the methacholine challenge was not done, yet spirometry was repeated 15 minutes after administration of a [[unkeyable].sub.2]-adrenergic inhaler (albuterol [salbutamol]; 400[unkeyable]g). An increase of 15 percent or more in [FEVsub1] from baseline was taken to indicate reversible airflow limitation. A bronchodilator rejoinder to albuterol was also performed in those patients unable or unwilling to discontinue their bronchodilator medications lengthy enough for a methacholine challenge to be performed (ranging from eight hours prior to challenge for inhaled [[unkeyable].sub.2]-adrenergic agents to 48 hours for slow-release theophylline preparations).

In patients who were still at work with continuing in all senses to similar amounts of the suspected causative agent as reported in the history and in those who had left if it be not that could return to the former work environment, studies of peak issue at home and at work were performed from one side of to the other a four-week period using a peak flowmeter (either a Wright or mini-Wright peak flowmeter [Armstrong Medical Industries], an Assess peak flowmeter or a Spira peak flowmeter [Trudell Medical]). Patients were asked to record the highest of three readings at place of abode and at work four times by day prior to the use of any inhalers and, additionally, if awakened from rest by symptoms. The subdues also recorded inhaler use and any changes in medication and indicated their location at the time of the readings. A reduction in peak emanate rates of 20 percent or more upon working days, compared with readings at the same time of day when along of work, on at least three days by means of week was considered a positive record.

Occupational inhalation challenges were performed in pickeded patients using the method of Pepy and Hutchcroft[14] in trying to imitate the workplace exposure in the laboratory. These were performed in patients who could not answer to their former workplace, in whom (1) the history was atypical for occupational asthma, (2) the history was suggestive, still no objective evidence for asthma was available, or (3) the suspected agent was not recognized to cause occupational asthma. Challenges were not performed in patients with irritant-induced asthma, as the implicated flats of chemicals were thought to be above the TLV