Lung function measurements in children - copsac

that small airways were not the distinguishing feature of later development of RSV
bronchiolitis. We recognize that the confidence interval of the comparison of baseline
lung function was wide with the risk of type 2 error.
Broughton et al. (2006) studied prospectively premature infants and found those who
had symptomatic RSV lower respiratory tract infection had worse lung function (higher
resistance using occlusion technique) prior to neonatal unit discharge compared to
controls but no difference in the lung volumes (functional residual capacity using
helium gas dilution system) (109). It is difficult to compare this study with our result
since we used a different lung function technique (forced expiratory maneuvers). Future
studies may consider investigating the sensitivity of other lung function tests such as for
example whole-body plethysmography measuring airway resistance.
Forced expiratory maneuvers was performed on 155 healthy infants by Jones and
colleagues with age range from 3 to 149 weeks (mean 48 weeks) (197). From the results
the study group calculated regression equations of the pulmonary functions versus body
length. In comparison, our data of FEV 0.5 was lower (66.3 ml (12.9)), mean length 56
cm); FEV 0.5 in Jones et al. data with corresponding length was approximately 120-160
ml/s. However, the study was done on cross-sectional data and it does not state clearly
how many infants there were in the lower age (length) group. The same applies for two
other studies where FEV 0.5 were obtained in 23 healthy infants (age range 7 weeks to 2
years) (198) and 26 healthy infants (age range 3 to 23 months) (187); the FEV 0.5 (length
60 cm) were respectively 95.0 ml and 121.2 ml. The two studies had few infants in the
lower age group. Studies using forced expiratory maneuvers have shown to discriminate
normal infants and wheezy infants or infants with cystic fibrosis (4, 187, 199).
Unfortunately, the lung functions of infants with airway disease were not comparable
with our data since the infants in these studies were older (age > 3 months).
A cross-sectional study of 37 normal infants found that a family history of asthma had a
negative effect on FEV 0.5 (198). Another study on 63 normal healthy infants found that
airway responsiveness in infancy was increased in families with history of asthma or
parental smoking (196).
Since our cohort only includes infants with asthmatic mothers the absolute levels of
lung function and bronchial responsiveness may not be representative of the general
population. However, this does not affect the purpose of comparing lung function of
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