Study objective: To compare lung function in
infants exposed to maternal smoking 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 of asthma in
parents or siblings.
pulmonary function tests were compared between the two groups. The
ratio of terminal to peak expiratory flow at tidal breathing at 25% of
the previous expiration remaining and the ratio of terminal to peak
expiratory flow with forced expiration at 25% of the previous
expiration remaining (FEF25/PFEF) were used to evaluate
peripheral airflow. A > 25% improvement in
FEF25/PFEF after a bronchodilator challenge test was
considered a positive response.
infants in both groups had evidence of peripheral airflow obstruction
with forced expiration. In infants exposed to maternal smoking, only 4
of 35 (11.4%) responded to a bronchodilator, compared 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 respiratory
system compliance, total respiratory system resistance, tidal volume,
and degree of peripheral airflow obstruction at tidal breathing or
after forced expiration in both groups.
Infants with exposure to maternal smoking and infants with a family
history of asthma have altered lung function, and a positive response
to a bronchodilator is one variable that seems to differentiate the two