Lung function measurements in children - copsac

Normative data
In the second part of the study a center effect could not be found, probably because
center no. 1 was corrected and center no. 6 did not participate. Atopy and smoking did
not significantly differ between centers (Table 2).
A British cohort study found that children of atopic parents and those with personal
atopy had impaired lung function at the age of 3 years, even in the absence of
respiratory symptoms (20). The high incidence of parental atopy in our study could be a
selection bias but we did not find a statically difference between atopic disposed and
non-disposed children.
Most papers have reported association between parental smoking and impaired lung
function in wheezing or asthmatic young children (57-59); some have investigated the
effect of parental smoking in healthy children (60-62) and found reduced lung function
in healthy infants. The ratio of smoking parents in the normative data corresponds the
smoking habit in the Danish population (63). The complex interaction of genetic and
environmental factors influence the development of airway disease and diminished lung
function (20, 64). We did not find an effect of the child’s history of atopy, parental
atopy or smoking on lung function in our study, this could be biased by either the
relatively small population, or the children with atopy, parental atopy or smoking could
be a selected healthy population.
We previously reported normative values from a population of 121 children 2-5 years of
age (12); mean sRaw (SD) was 1.31 (0.20). Z-score was -0.5 between the two data sets.
No other reference value for sRaw TOT has been reported, other studies have reported
values of sRaw max (54, 65, 66).
The variance was higher in the new collected data (SD 0.33) compared to previous
reported (SD 0.2). This could be explained by a small non-significant center variance.
The previous population differs from the current in several following aspects: 1)
Measurements were done at one center; 2) exclusion of children exposed to tobacco
smoke and anyone with a history of eczema or doctor-diagnosed atopy in first-degree
relatives; 3) The study included more 2- and 3-year-old children; many of these
measurements had an accompanying adult in the whole-body plethysmograph. The
current data only included children who performed a lung function measurement alone.
The exact same equipment (unchanged hardware and software) at center no. 3 was used
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