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8.1
Chapter 8: Exhaled nitric oxide in healthy and asthmatic children
Introduction
The protocol was now established and I felt we would be able to measure NO in a
reproducible manner in children by standardising all of the parameters discovered to alter NO
readings. Initially I wanted to measure exhaled NO in healthy children: that is children with
no respiratory diagnosis or any acute or chronic respiratory symptoms. This was to confirm
that the technique was possible in children and to confirm some of the findings from the adult
studies presented in the previous chapters. Included was a comparison of the results from the
direct versus t-piece sampling systems that incorporated a change in flow. I then wanted to
compare the exhaled NO levels from these healthy 'control' children to those from asthmatic
children in two categories; children on bronchodilator therapy only versus those on regular
IHCS. Finally I wanted to measure the exhaled NO pre and post IHCS cornmencement in any
child who was on bronchodilator therapy only but who clinically required the introduction of
a preventer for asthma control.
At the time of corlmencement of this research there had been very little published on exhaled
or nasal NO in children. There had been a series of studies looking at the levels of NO from
nasal and sinus passages. High concentrations of NO were found when aspirating air from the
sinuses of five patients undergoing surgery at 9.1 parts per million (note that most of the
exhaled NO reported is measured in parts per billign) (Lundberg, Farkas-Szallasi et al. 1995).
An age-dependent increase in mean nasal NO plateau concentrations was also demonstrated
in 49 subjects with an age range of 0-62 years, thought to be consistent with the development
and pneumatisation of the paranasal sinuses (diagram included in the next chapter as Figure
9.2) (Lundberg, Farkas-Szallasi et al. 1995). The NO levels sampled directly from one nostril
and in exhaled air were also significantly less in four children with Kartageners syndrome at
4ppb when compared to 20 healthy children at22lppb (Lundberg, Weitzberg et al. 1994).
The following experiments ran from 1995-1997. At the time that we published these findings
in 1996 and through 1997, a number of research groups also published results of their
investigations into exhaled and nasal NO in children. In the main these were comparisons
between control subjects and those with respiratory diseases. In the next section, I will present
the subjects, protocols and results from the studies we conducted in healthy children and
discuss the findings comparing with these other results from the literature. In the second part
of the chapter I will present the literature available from studies in groups of adult asthmatics
as again these were published ahead of any results in children. The procedures followed were
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