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Zetterstrom et al. 1994; Kharitonov, Yates et al. 1995; Massaro, Gaston et al' 1995;
Kharitonov, Chung et al. 1996; Martin, Bryden et al. 1996; Massaro, Mehta et al' 1996;
Robbins, Floreani et al. 1996; Kharitonov, Rajakulasingam et al. 1997). In the experiments
above we set out to assess whether the pattern of NO excretion was similar in children as
determined in adults. In 39 children with no known respiratory problems it was possible to
measure exhaled No with mean levels of 49ppb (direct) and 29.7ppb (t-piece). I have also
shown that there was a significant increase in mean NO concentrations to t26.7ppb (direct)
and to l09.5ppb (t-piece) in asthmatic children receiving bronchodilator treatment only' There
was a significant decrease in children on regular IHCS therapy with mean NO levels of
48.7ppb (direct) and of 42.5ppb (t-piece). There was no difference between the exhaled No
levels of the healthy children and the stable asthmatics on regular IHCS therapy. There was
no significant difference in the mean age of the children in the three groups, although the age
range of the children recruited from the outpatient clinics was greater than those in the control
group. So while the effect of puberty and age was controlled for the healthy children' it is
possible that this may have affected results in the other two groups (Lundberg, Farkas-Szallasi
et al. 1995; Franklin, Taplin et al. 1999). The lowest age of a child that we successfully
studied was six years. All of the testing was completed in the mornings between 1000 hours
and 1300 hours so we could disregard any concerns regarding circadian rhythm effects
(Mattes, Storm van's Gravesande et al.2oo2). The pattern of No exhalation appeared to be
the same as the patterns seen in the adult subjects, and the pattern was the same in asthmatic
children as in healthy children, although the levels seen in children were lower' Similar to the
results from the adult subjects in the methodological experiments' we saw a reduction of the
NO levels between the direct and t-piece method of sampling in all the groups of children'
However the magnitude of the reduction was different. There is an increase from 440mls/min
in the direct sampling technique to 665mls/min in the t-piece sampling method, an increased
flow of 517o. This led to a SOVo reduction of the No levels in the adult experiment
(methodological experiment one described in Chapter 6), a 407o percent reduction in the
healthy control children, a 24Vo reduction in the asthmatic children on bronchodilator
treatment only and an 8Vo reduction in the asthmatic children on IHCS therapy' The variation
seen when measuring children was greater than that in adults, and there was a wide range of
exhaled No levels within all three paediatric groups. I have previously discussed one boy who
was an outlier in the group of healthy children. one subject recorded as an asthmatic on
bronchodilator treatment only had mean exhaled levels of 14'4ppb via the direct method
which was 53ppb lower than the next value, and 13.4ppb via the t-piece method which was
l7ppb lower than the next value. She had not had any episodes of asthma for two years and
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