Sulphur dioxide sensitivity and plasma antioxidants in adult subjects withasthma

Objectives-To screen adult subjects with asthma for sensitivity to inhaled sulphur dioxide (SO2) and identify subject characteristics associated with that sensitivity. Medication use, symptoms, and plasma antioxidant nutrient s between SO2 responders and non-responders were compared. Methods-Adult subjects (ages 18-39 years) with asthma were exposed to 0.5 p pm SO2 for 10 minutes during moderate exercise. Pulmonary function tests an d symptom ratings were assessed before and after exposure (n=47). A subject was classified as sensitive to SO2 if forced expiratory volume in 1 second (FEV1) showed a drop greater than or equal to 8% over baseline. Blood samp les were obtained from subjects (n=38) before the SO2 challenge; plasma asc orbate, alpha-tocopherol, retinol, carotenoids, and lipids were measured. Results-Of the 47 subjects screened, 53% had a drop in FEV1 greater than or equal to 8% (ranging from -8% to -44%). Among those 25 subjects, the mean drop in FEV1 was -17.2%. Baseline pulmonary function indices (FEV1% of pred icted and FEV1/FVC% (forced vital capacity)) did not predict sensitivity to SO2. Although use of medication was inversely related to changes in pulmon ary function after SO2 (p<0.05), both SO2 responders and non-responders wer e represented in each medication category. Total symptom scores after expos ure were significantly correlated with changes in FEV1 (p<0.05), FVC (p<0.0 5), and peak expiratory flow (PEF) (p<0.01) but not forced expiratory flow between 25% and 75% vital capacity (FEF25-75). Plasma beta-carotene concent rations were inversely associated with PEF values and ascorbate concentrati ons were inversely associated with FEV1 and FEV1/FVC (p=0.05 in all cases). High density lipoprotein concentrations were positively correlated with FE V1% of predicted (p<0.05) and inversely correlated with change in FEF25-75 (p<0.05) after SO2. Conclusion-These results show that the response to SO2 among adults with mi ld to moderate asthma is very diverse. Severity of asthma defined by medica tion category was not a predictor of sensitivity to SO2. Lung function valu es were associated with beta-carotene and ascorbate concentrations in plasm a; however, plasma antioxidant nutrient concentrations were not associated with sensitivity to inhaled SO2.