Comparison of lung function in infants exposed to maternal smoking and in infants with a family history of asthma

Study objective: To compare lung function in infants exposed to maternal sm oking with lung function in infants with a family history of asthma. There are no published studies comparing lung function in both groups. Design: Cross-sectional study. Setting: A tertiary pulmonary care center at a children's hospital. Patients: One hundred five infants with daily wheezing. Thirty-five infants had persistent exposure to maternal smoking, and 70 had a family history o f asthma in parents or siblings. Measurements: Infant pulmonary function tests were compared between the two groups. The ratio of terminal to peak expiratory flow at tidal breathing a t 25% of the previous expiration remaining and the ratio of terminal to pea k expiratory Row with forced expiration at 25% of the previous expiration r emaining (FEF25/PFEF) were used to evaluate peripheral airflow, A > 25% imp rovement in FEF25/PFEF after a bronchodilator challenge test was considered a positive response, Results: Most infants in both groups had evidence of peripheral airflow obstruction with forced expiration. In infants exposed t o maternal smoking, only 4 of 35 (11.4%) responded to a bronchodilator, com pared to 51 of 70 (72.9%) in the group with a family history of asthma (p < 0.0005). There was no statistically significant difference in total respir atory system compliance, total respiratory system resistance, tidal volume, and degree of peripheral airflow obstruction at tidal breathing or after f orced expiration in both groups. Conclusion: Infants with exposure to maternal smoking and infants with a fa mily history of asthma have altered lung function, and a positive response to a bronchodilator is one variable that seems to differentiate the two gro ups.