[Effect of passive smoking on pulmonary function in the asthmatic child]

Few studies refer to pulmonary function in asthmatic children exposed to environmental tobacco smoke (ETS). Some authors have found lower FEV1 and FEF25-75 values in asthmatic children exposed to ETS. The objective of this study was to evaluate pulmonary function parameters between asthmatic children exposed and not exposed to ETS.

A case-control study in children between 3 and 19 years of age, with a ratio of 1:1 of cases versus control, was carried out. Cases were defined as asthmatic children with at least one of the following criteria: FVC < 85%, FEV1 < 85%, PEF < 85% or FEF25-75 < 60%. Controls were asthmatic children with none of the above mentioned criteria. Measurement of exposure was carried out both directly by assessment of capillary blood COHb in both parents and the child and indirectly through a questionnaire about smoking habits. Measurement of effect was by pulmonary function (forced spirometry) and a scale of clinical symptoms. The statistics used included descriptive statistics, Chi square test, Student's-t and ANOVA.

Three hundred and twelve children were studied (mean age 9.01 +/- 3.45 years). Parental CoHb results correlated with the number of cigarettes smoked (p < 0.01). ETS exposure correlated with the children's COHb values (p < 0.01). ETS exposed children had lower pulmonary function values, OR for exposure was 1.84 (1.12-3.03).

1) We have validated a questionnaire about smoking habits. Smokers have higher COHb values. 2) We found a weak correlation between exposure to ETS (number of cigarettes and maternal COHb) and the child's COHb. 3) Pulmonary function in asthmatic children is influenced by parental smoking habits.