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need for methodological experiments' and from the first methodological experiment
conducted and described in the last chapter.
The effect of pressure -
to be assessed both by applying a calibration gas under pressure
to the NO analysers and by looking at the effect of expiratory mouth pressure in NO
results.
The effect of the ambient NO when high - this was not always standardised and
sometimes not reported in early literature and could have been a source of error in results
presented by different groups.
The effect of water consumption - this was due to a chance finding during one
experiment, where a person drank some water during a series of test exhalations and the
NO results dropped significantly for the next readings. I considered that asking both
healthy and, more particularly, subjects with any respiratory disease to inspire and exhale
fully may well lead to coughing in some for which a corlmon response is to give a glass
of water. If this then resulted in decreasing the levels of subsequent NO measurements,
this could easily skew results.
The peak exhaled NO was shown to have a good correlation with the area under the NO curve
in the previous experiment, so I elected to proceed with the peak measurements as they were a
more straightforward measurement, without the possibility of introducing error when tracing
around a curve, drawing a line for zero along the lower edge of the recording and then
calculating the area within these boundaries. I will summarise the subjects, ethics and
statistics again at the beginning of this chapter pertaining to all the investigations in the adult
subjects. For each experiment I will present the hypothesis, aim, procedure and results. I will
discuss the results and how they contribute to findings in the literature of all four experiments
at the end of the chapter. As the direct and t-piece experiment was deemed 'methodological
experiment one', these are labelled methodological experiments two to five.
7.2
Ethics. subjects. calibrations and statistical analysis
The studies received prospective approval by the Royal Brompton Hospital Ethics Committee
and informed consent was obtained from each of the volunteer subjects.
In total, twenty healthy volunteers (mean age 35.9 years, range 18-52 years, 9 males) took
part in these methodological studies. Following consent, each subject completed a
questionnaire (see Appendix l). They were non-atopic with no history of respiratory or
cardiac disease and taking no medication. All had normal spirometry (Compact Vitalograph,
Vitalograph Limited, Buckingham, United Kingdom) and results are presented as percent
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