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an advisor for this work and main supervisor for other research done at the time (publications
listed as Appendix 1), and Dr Elliot Shinebourne also acted as advisor, particularly in the
early stages.
5.3 Direct versus reservoir measurement
The concept of the proposed methodological experiments was to have a subject exhale into
teflon tubing connected to NO, CO2, flow and mouth pressure meters allowing measurement
of each. It was established that all the equipment could come directly off the mouth piece,
with the exception of flow connector. This was due to the necessity of the addition of a
rotameter to provide a visual feedback guide for the subjects regarding expiratory flow and
added a level of complexity to the system. In view of this, I elected to do a series of
experiments in which one set of exhalations was connected directly to the NO analyser,
pressure and COz monitors (known as the 'direct method') and a second set of exhalations
where a t-piece system enabled the additional measurement of flow (known as the 't-piece
method' or 't-piece sampling system'). A comparison of the two techniques is shown
diagrammatically in the next chapter in Figure 6.5. Below is a photograph of one of the
children performing the procedure with the analysers labelled in Figure 5.3. Unfortunately I
did not take any photographs of the subjects during the methodological experiments.
Figure 5.3: Photographs of one of the children performing the exhalation