Parental smoking
This is the first study to show that severity in SAB infants is
associated with the fact that their parents smoked. The differences
found in the rate of IMV and PBI between these 2 groups were clinically
relevant. Infants with SAB whose parents smoked needed to be intubated
in 27 additional cases per 100 patients compared with those whose
parents did not smoke. This result means that 58% of the intubations in
the group of infants whose parents smoked were due solely to the fact
that their parents smoked.
In addition, IMV duration and PICU length of stay were also
significantly higher in smoke-exposed patients.
The higher risk for ETI and need for IMV can be most likely explained by
the fact that patients exposed to tobacco smoke have a higher bacterial
superinfection rate, as we can see in ETA cultures of intubated patients
(71% positive if parents smoked vs. 21% positive if the parents did
not smoke).
Both groups have similar characteristics. The only significant
difference between these two groups was gestational age. Although there
were slight differences in gestational age, the median of both groups
corresponded to term infants.
Cigarette smoking has been shown to be a substantial risk factor for
important bacterial and viral airway infections. The mechanisms by which
smoking increases the risk of infections include structural changes in
the respiratory tract and a reduction in the immune
response18.
ETS exposure is known to be an important risk factor for childhood lower
respiratory tract infections19. Passive ETS
exposure has been associated with lower oxygen saturation and higher
clinical severity scores20, and it significantly
increases the risk of hospitalization for bronchiolitis in the first
year of life21. Furthermore, maternal cigarette
smoking during pregnancy puts children hospitalized with bronchiolitis
at significantly higher risk of intensive care use, and postnatal ETS
might exacerbate this risk22.
The findings in our study imply that in infants with SAB, the risk of a
severe event, such as intubation, is increased by ETS exposure. All
these infants survived because they received appropriate treatment in a
PICU. Bronchiolitis is a significant cause of respiratory
disease worldwide, and appropriate access to a PICU is not guaranteed
for all infants.
This study has some limitations. The sample we analyzed consisted of
only 102 patients. However, it represents the complex PICU population
with SAB, a situation that physicians face on a daily basis, and this
sample has similar characteristics to others
reported23,24.
Memory-based parental reports of short-term ETS exposure can play an
important role in quantifying ETS exposure in infants and
children25. The degree of exposure to tobacco smoke is
not known, nor is the duration of time the patients were exposed.
Further studies are needed to measure the ETS exposure of the children
who have AB, and to know if this risk factor could be removed,
consequently reducing the severity of bronchiolitis in these patients,
and the number of patients requiring IMV or PICU stay.