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7.4.4 Results
There was an increase in the peak NO signal of 5.6ppb seen across the range from 4mmHg to
4OmmHg of pressure when the calibration gas was applied to the NO analyser in increments
of 4mmHg, with the mean and standard deviation shown for each level in Figure 7.3.
Figure 7.3: The etfect of pressure on the calibration gas measurement
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The mean and standard deviation of the NO levels of a known calibration gas with a concentration of
110ppb delivered to the NO analyser at incremental pressures with an increase of 5.6ppb
demonstrated over this range.
The mean peak concentrations of NO obtained at the four mouth pressure settings were
61.0ppb (SEM 15.1) at 4mmHg,55.2ppb (SEM 12.3) at 8mmHg, 47.3ppb (SEM 8.4) at
l2mmHg and 4O.lppb (SEM 7.2) at l6mmHg (see Table 7.2).There was no significant
difference in the exhaled NO levels obtained at each mouth pressure. Figure 7.4 shows that in
the majority of patients NO levels did not change. However in two subjects who found the
higher pressures difficult to sustain (see reduced duration of exhalation in the Table 7.3 for
these two subjects at this higher pressure) there was a drop in NO as mouth pressure
increased. There was no difference between the first baseline and repeated final baseline of
NO when the mouth pressure was the same (p = 0.M 95Vo CI -16.7, 15.6) thus excluding an
order effect (see Table 7 .4). There was no significant difference between the flows measured
at the different mouth pressure readings. The peak expired CO2 at different mouth pressure
levels tended to decrease. The mean peak values were 5.907o (SEM 0.83) at 4mmHg, 5.83Vo
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