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only those measured by mouth or lower respiratory tract rather than nasal or sinus measurement
which will be discussed in a later chapter.
(exp = expiratory, IHCS = inhaled corticosteroids, insp = inspiratory, rg = nanogram, ppb = parts per
billion, s = seconds, single responders = edrly asthmatic response only, late responders = both early
and late asthmatic response, URTI = upper respiratory tract infection).
6.4 The aims of the exhaled nitric oxide methodological experiments
The following methodological experiments were therefore designed and conducted in adult
subjects to try and answer two main questions:
1. Were NO and CO2 produced from the same region within the lung?
2. Which technical factors during measurement led to changes in the NO results and
therefore would require standardisation in future research in this area?
The aims of the methodological investigations were:
L. To determine whether exhaled NO could be measured by the chemiluminscence analyser
now modified from its original purpose of measuring NO in air pollution.
2. To compare the exhalation pattern of NO versus COz from a series of single exhalations.
3. To compare the results of NO using the peak level versus the area under the curve of the
recording trace.
4. To compare the results of NO and COz between two methods of measurement; either
direct exhalation to the NO analyser (which also allowed measurement of CO2, and mouth
pressure) or exhalation via a t-piece system (which measured these parameters with the
additional measurement of expiratory flow).
5. To assess the reproducibility of the NO and COz measurements.
6. To investigate whether altering the expiratory flow changed the exhaled NO levels
measured.
7. To assess whether pressure had any effect on the exhaled NO levels by two methods:
(a) Delivering the calibration gas at different pressures to the NO analyser.
(b) Altering the expiratory mouth pressure voluntarily by adult subjects.
8. To investigate whether ambient NO levels affected exhaled NO levels.
9. To investigate whether water consumption immediately before exhalation changed the NO
results obtained (this was added in response to a chance finding).
The experiments and results from aims one to five listed above will be detailed in this chapter.
The experiments and results conducted to answer aims six to nine where a specific single
condition was varied to assess the effect on the exhaled NO levels obtained are detailed in
Chapter 7.
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