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standard error of the mean (SEM) and ranges given. A p-value of less than 0'05 was
considered significant.
6.6
o
a
o
Methodological exPeriment one
Direct versus t-piece NO measurement
Peak NO versus area under the NO curve
Exhalation patterns of NO versus COz
6.6.1 Hypotheses
l. The levels of NO measured in exhaled air are dependent on the techniques of
measurement.
Z. There will be good correlation between the peak NO levels and the area under
recording curve of the NO measurement.
3. Curves for NO and COz in a single exhalation should be identical if they
predominantly being produced in the same department within the lung.
6.6.2 Aims
1. To compare exhaled NO levels measured by two different techniques'
Z. To compare results of NO measured as peak level with area under the curve.
3. To compare the peak levels and curves of NO and COz in a single exhalation.
6.6.3 Procedure
Each subject abstained from food and drink for four hours prior to the experiment. The
experiments were made if the ambient level of No was less than 10ppb, and all the testing
was done with inhalation from ambient room air. The procedures as described in the previous
section for starting and calibrating the analysers were made before and after each subject. The
exact procedure followed is as described above in Section 6.5.2. Twelve subjects were
enrolled and each subject continued until five sets of measurable exhalations were made for
each set of conditions with the first set being determined randomly by tossing a coin (heads -
direct, tails -
t-piece). This was followed after a five minute break by measuring exhalation
under the other set of conditions. Again, after a five minute break, the first conditions were
measured again. Expiratory mouth pressure was requested to be voluntarily kept at 4mmHg
by the subjects and was measured on the chart recorder. During the exhalations into the t-
piece system, the subjects were also requested to maintain a set expiratory flow by watching
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the