Lung function measurements in children - copsac
Lung function measurements in children - copsac
Lung function measurements in children - copsac
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Mean<strong>in</strong>g of the study<br />
Acute RSV bronchiolitis may occur <strong>in</strong> otherwise healthy <strong>in</strong>fants. Infants with bronchiolitis are at<br />
significant risk for subsequent recurrent wheez<strong>in</strong>g and childhood asthma (11, 50-53).<br />
It is not known whether viral bronchiolitis is causatively related to asthma or simply identifies <strong>in</strong>fants<br />
at risk for subsequent wheez<strong>in</strong>g from an atopic predisposition or pre-exist<strong>in</strong>g abnormal lung<br />
<strong>function</strong> (54, 55). Infants with impaired pulmonary <strong>function</strong> at one month of age was reported to be<br />
prone to recurrent wheezy episodes and asthma (8-11, 13, 14, 56, 57). Therefore it has been assumed<br />
that acute bronchiolitis or wheeze develop due to pre-morbid abnormal pulmonary lung<br />
<strong>function</strong> consistent with smaller airway size (11, 12, 15, 18, 19). But these are <strong>in</strong>direct evidence as<br />
cl<strong>in</strong>ical wheez<strong>in</strong>g illness was used as end-po<strong>in</strong>t<br />
This is the first study to look specifically at neonatal lung <strong>function</strong> before RSV bronchiolitis. Our<br />
study showed no association between early lung <strong>function</strong> (FEV 0.5 and bronchial hyperresponsiveness)<br />
and subsequent RSV bronchiolitis. This could mean that small airways were not the dist<strong>in</strong>guish<strong>in</strong>g<br />
feature of later development of RSV bronchiolitis. We recognize that the confidence <strong>in</strong>terval<br />
of the comparison of basel<strong>in</strong>e lung <strong>function</strong> was wide with the risk of type 2 error.<br />
Broughton et al. (2006) studied prospectively premature <strong>in</strong>fants and found those who had symptomatic<br />
RSV lower respiratory tract <strong>in</strong>fection had worse lung <strong>function</strong> (higher resistance) prior to<br />
neonatal unit discharge compared to controls but no difference <strong>in</strong> the lung volumes (<strong>function</strong>al residual<br />
capacity) (17). It is difficult to compare this study with our result s<strong>in</strong>ce we used a different<br />
lung <strong>function</strong> technique. Future studies may consider us<strong>in</strong>g other lung <strong>function</strong> tests such as for<br />
example whole-body plethysmography measur<strong>in</strong>g airway resistance.<br />
Studies us<strong>in</strong>g forced expiratory maneuvers have shown to discrim<strong>in</strong>ate normal <strong>in</strong>fants and wheezy<br />
<strong>in</strong>fants or <strong>in</strong>fants with cystic fibrosis (58-60). These studies were done on older <strong>children</strong> (age > 3<br />
months) and therefore not comparable with our data.<br />
A cross-sectional study of 37 normal <strong>in</strong>fants found that a family history of asthma had a negative<br />
effect on FEV 0.5 (61). Another study on 63 normal healthy <strong>in</strong>fants found that airway responsiveness<br />
<strong>in</strong> <strong>in</strong>fancy was <strong>in</strong>creased <strong>in</strong> families with history of asthma or parental smok<strong>in</strong>g (56). S<strong>in</strong>ce our cohort<br />
only <strong>in</strong>cludes <strong>in</strong>fants with asthmatic mothers the absolute levels of lung <strong>function</strong> and bronchial<br />
responsiveness may not be representative of the general population. However, this does not affect<br />
the purpose of compar<strong>in</strong>g lung <strong>function</strong> of <strong>in</strong>fants who later develop RSV bronchiolitis and <strong>in</strong>fants<br />
7