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Figure 7.6: Photographs of the changing ambient NO concentration recordings
The ambient air NO concentration ranged from 91-200ppb during these experiments with a
mean background NO concentration of 134.5ppb (SEM 11.9). The background concentration
of the reservoir system was lppb (range 0-2ppb, SEM 0.2). Three subjects completed the
experiment (mean age 37 years, all female). The mean plateau NO concentrations during the
first set of exhalations with the high background NO was 94.9ppb (SEM 3.4ppb, range 84-
l0lppb). The mean plateau exhaled NO concentration in the set of exhalations during which
both the machine and subject were sampling from the NO-free reservoir system was 123.lppb
(range 103-l64ppb, SEM I9.4). The mean plateau NO concentrations during the last set of
exhalations with the high background NO was 99.9ppb (SEM 20.5ppb, range 53-15lppb).
Figure 7.7 shows a typical trace for one subject showing the rise to NO plateau during an
exhalation made from the reservoir system and the fall to an NO plateau during an exhalation
made from the high ambient NO. In the direct method, the NO level measured from the
reservoir system was 41ppb (95Vo CI I9.9,62.7) greater than the measurements made before
and after the reservoir system was used (see Figure 7.8). There were no significant differences
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