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7.5
7.5.1 Hypothesis
1. Exhaled NO measurements will be affected by the ambient NO level'
7.5.2 Aims
l. To compare NO levels measured at a time of high and low ambient NO concentrations
with the high level being background and low level provided by breathing from a
reservoir system containing a low NO concentration'
7.5.3 Procedure
Three adult volunteers (all females) were enrolled and all measurements were made by the t-
piece sampling sYstem.
The first set of exhalations was carried out in the standard manner:
r The subject abstains from food and drink for 4 hours prior to the experiment'
o The subject sits at rest for at least 5 minutes'
o The chart recorder is started 30 seconds prior to each exhalation to document baseline pre
exhalation measurements.
o The subject puts on nasal clips 5 seconds prior to each exhalation and exhales by mouth,
and removes the clips between exhalations'
o The subject inhales to total lung capacity then performs a slow vital capacity manoeuvre
to residual volume over 30-60 seconds.
o The exhalations occur 3 minutes apart.
o The subject exhales at a constant mouth pressure of 4mmHg voluntarily controlled by the
subject observing the pressure gauge and keeping it at level '10' on the scale'
o The subject exhales at a constant flow at 5OOmls/min voluntarily controlled by the subject
observing the rotameter, keeping it at a level at '3' on the scale'
o At the end of each exhalation the connections are reversed to allow the subject and the
analysers to continue to sample from the low NO reservoir'
o The subject was breathing ambient air when the natural background level of NO was high
- above the NO concentration normally measured on exhalation.
o The subject continues until 5 exhalations adequate for measurement are made'
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