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In comparison to the early literature in the adults, the research groups studying children
appeared to more often consider the effect of ambient NO. Our experiments were only
undertaken if the ambient NO was less than 10ppb, as I had already shown in the previous
methodology experiment in adults (Section ?.6) that the ambient NO did affect the exhaled
NO levels. Similarly, Grasemann et al commented that "In preliminary experiments we
observed that the higher NO concentrations in ambient air were associated with increased
exhaled NO concentrations." (Grasemann, Michler et al. 1997). Ambient NO in this paper
was reported at between two and22 ppb in one paper which authors thought unnecessary to
take into account, but the exhaled levels in this paper were 1.1 to 23pb in the control children
which was exactly this ambient range (Balfour-Lynn, Laverty et al' 1996)' One group noted
that when measuring the exhaled levels in their control group it did not change when
measured in ambient or NO-free air, thus all their subsequent experiments were caried out
inhaling room air. However at the time their ambient NO level was reported as 3'95ppb +/-
0.98ppb and their NO free m at 3.97 +f 1.14ppb so there was no difference in the inhaled
levels and this ambient level may have changed over time (Nelson, Sears et al.1997} Finally
one group stipulated that they did all their measurements with the children inhaling No-free
air (Baraldi, Azzolin et al. 1997),
we found no correlation between exhaled No levels and gender or lung function parameters.
Nelson et al also found that there was no correlation between NO and height, weight, gender
or FEVr in either the control or asthmatic children (Nelson, Sears et al. 1997). Balfour-Lynn
et al found no correlation between exhaled NO and FEVr or FVC across control and CF
groups of children (Balfour-Lynn, Laverty et al' L996)'
In our study, we have documented that exhaled NO could be measured in children, reporting
normal values obtained with these techniques. As the continuation of this research, I then
moved on to investigate the exhaled NO levels in asthmatic children'
8.5
8.5./ Background
presence of higher levels of exhaled No in asthma were first indicated in two animal models
where exhaled NO significantly increased following induction of an asthma exacerbation
using ova-albumin sensitised guinea pigs and rabbits (Persson and Gustafsson 1993; Endo'
uchido et al. 1995). There followed a number of publications in adult subjects showing that
exhaled No levels appeared to be raised in patients with asthma when compared to healthy
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