Exercise-induced asthma among Thai asthmatic children.

BACKGROUND: Approximately seventy per cent of asthmatic children from temperate climates, with normal lung function, have exercise-induced asthma (EIA). There is certain evidence to suggest that EIA may be less frequently encountered among children who live in tropical climates. Prevalence of EIA in Asian asthmatic children has never been thoroughly studied. OBJECTIVE: To study the prevalence of EIA among Thai asthmatic children. METHOD: A prospective study was performed to determine the prevalence of EIA in 44 Thai asthmatic children who were able to perform the spirometric maneuver. Subjects were randomly selected asthmatic children from the Pediatric Allergy Clinic, Department of Pediatrics, Siriraj Hospital. They were subjected to exercise testing on a steady state, motor-driven treadmill for 6 minutes (mean speed +/- SD = 3.7 +/- 0.4 km/h, mean level of inclination + SD = 15.0 +/- 5.2 degrees). The testing was conducted in a temperature-controlled (mean temperature +/- SD = 24.4 +/- 0.8 degrees C) and humidity-controlled environment (mean relative humidity +/- SD = 41.7 +/- 2.1%). Lung function tests were performed before exercise, immediately after and at 3, 5, 10, 15, 20 and 30 minutes after exercise. Results of the lung function test were calculated as per cent falls of forced expiratory volume in 1 sec (FEV1), peak expiratory flow rate (PEFR), and forced expiratory flow at 25 per cent-75 per cent (FEF50) from baselines. EIAs were diagnosed when drops of FEV1, PEFR and FEF50 were greater than 20 per cent, 25 per cent and 25 per cent from baseline values, respectively. RESULTS: Of the 44 patients studied (31 boys and 13 girls; mean age 11.9 years), 34 per cent had mild asthma. Fifty-nine per cent had moderate asthma and 7 per cent had severe asthma. Eleven patients (25%) had EIA diagnosed by significant falls of FEV1's (26 +/- 12.6%), whereas, 13 patients (30%) and 20 patients (45%) had EIA defined by significant drops of PEFR's and FEF50's, respectively. A total of 23 patients (52%) had EIA by one or more diagnostic criteria. Peak times for EIA as diagnosed by FEV1, PEFR and FEF50 occurred at 3, 10, and 10 minutes respectively, after exercise. Most EIA episodes observed were of mild degree. CONCLUSIONS: The prevalence of EIA in Thai children is much lower than figures reported in studies from Western countries. By using a significant fall of FEV1's as the diagnostic criteria, only 25 per cent were diagnosed as having EIA. By PEFR and FEF50 criteria, percentages of EIA increased to 30 per cent and 45 per cent respectively. Screening for EIA, therefore, may not be an appropriate diagnostic tool for the diagnosis of childhood asthma in tropical climates.

Vacuum cleaning does not sufficiently reduce mite allergens from beddings.

INTRODUCTION: Conflicting results exist with regard to the efficacy of vacuum cleaners on the removal of mite allergens from bedding. OBJECTIVES: The authors prospectively compared a short term efficacy of two types of regular vacuum cleaners (National-N and Hoover-H) with a specialized cleaner (Vorwerk-V) in the removal of mite allergens from mattresses. MATERIAL AND METHOD: Thirty-five dormitory beds with high mite allergen concentrations at the baseline period (month 0) were selected. They were matched into three groups according to group I mite allergen concentrations (N 11 beds, H 12 beds, V 12 beds). Vacuuming was performed on months 1 and 4 by the assigned vacuum cleaner in each group. Immediately after, mattresses were vacuumed by a reference cleaner (another National vacuum cleaner) at both months. Vacuuming was performed over the entire bed for 2 minutes/square meter. Group I mite allergens (sums of Der p 1 and Der f 1) were measured; concentrations and total mite allergens removed by the tested cleaners as well as by the reference cleaner, at various time points, were compared. RESULTS: Ability to remove mite allergens by vacuum cleaners depends on weight of dust removed and also on mite concentrations in the dust samples. Despite the fact that H and V appeared to remove higher mite allergens than N, such differences were not statistically significant (p > 0.05), both at month 1, and 4. Surprisingly, mattress mite concentrations removed by both high capacity cleaner groups (V & H) increased at month 4, whereas, it remained unchanged in the third group (N). This increase led to a concomitant increase in total allergen removed by V and H. Nevertheless, remaining total allergens in the mattresses in V and H, as judged from the amount of allergens obtained by the reference cleaner, increased at month 1 and 4 compared to baseline values (p < 0.05), whereas, no change was observed in N. CONCLUSION: Although high capacity vacuum cleaners removed a large amount of mite allergens from mattresses, they did not sufficiently reduce mattress mite allergen burden as determined by the reference cleaner during this short term study.