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Delay time: the time between turning on the switch and the onset of the analyser
signal
Response time: the rise time that from onset of signal to 95Vo of plateau or a square wave
The experiment was repeated 10 times in all with times recorded for each of the analysers.
Results are presented in the Table 5.1.
Table 5.1: The delay and response time of the NO, COz, mouth pressure and flow meter analysers
used
Analyser Delay time Response tlme
NO analyser Model2107 5.9 seconds
(SEM 0.8 s)
CO2 Morgan capnograph 0.11 seconds
(SEM 0.003 s)
Medex Staingauge pressure
transducer (mouth pressure)
SEM = standard error of the mean, s = secondsr lrls = milliseconds
This established that the delay time for the NO analyzer at 5.9 seconds (SEM 0.8s), and95Vo
response time at 0.5 seconds (SEM 0.1s) showed the NO analyser responded much more
slowly than the CO2 analyser at a delay time of 0.1 I seconds (SEM 0.003s) and 95Vo response
time at 0.41 milliseconds (SEM 2.9ms). It has to be remembered that the delay time was
influenced only by the time that it took for the gases, flow or pressure to get to the analysers
and the time to cornmence registering the change. The response time should be a square wave
for 'on/off' phenomena like the pressure and the flow, but could be influenced by other
parameters in the measurement of the gases. The pattern of excretion through the exhaled
breath was unknown for NO, and was known to increase with the duration of exhalation for
COz. So while the response time was measured with these two gases, it was the delay time
that was the key factor. In essence it meant that when comparing the NO and COz recordings,
an allowance needed to be made for the difference in time delay of the measurements from
each machine and for the 2mm offset of the pens on the recorder.
Finally, confirmation of the detection of the appropriate gases was checked for the two
analysers. Cylinders of IOOVo Oz, 5.9Vo COz and 37ppb of NO were run through the NO
analyser and the CO2 analyser with only the NO gas detected and the others giving a zero
reading on the NO analyser machine and only the COz gas detected with the others giving a
zero reading on the CO2 analyser machine.
7.3 milliseconds
(SEM 0.2 ms)
Platon flow meter 40.2 milliseconds
(SEM O.8 ms)
118
Seconds
(SEM 0.1 s)
41 milliseconds
(SEM 2.9 ms)
No appreciable delay
No appreciable delay