View - ResearchSpace@Auckland - The University of Auckland

Calibration pressures: the test port of the pressure transducer is on the opposite side of the
transducer to the mouthpiece - to mimic an increase in mouthpiece pressure it is necessary
to create an equivalent negative pressure at the test port -
move the wheel in the direction
indicated by the vacuum alrow to the right of the wheel - a negative figure is noted on the
generator display -
increase the vacuum by increments of 2mmHg from 0-20 mmHg and
run the chart paper at each level and mark on the chart record.
o Ensure that when calibrating the trace does not drift down which suggests a leak and in
this case recheck the joints.
o At the end, disconnect the generator and switch it off to save the batteries and ensure the
needle on the pressure monitor is on zero (see Figure 6.1).
For the testing the chart speed can be set 20mm/min or 5Omm/min - the latter should be used
for the subjects.The scaling factor on the CO2 channel on the pen recorder should be set to l0
volt full scale deflection (i.e. set the the toggle switch to V and the pointer on the votage knob
pointing to l0 on the V scale), and that of the NO channel to 500mV. The scale of the NO
channel will have to be changed if the calibration gases contain more than 490 ppb NO /nor
required during this timel.
At the end of the study:
o Repeat the calibrations in reverse order immediately the study has finished.
r Check that the gas cylinders are off.
o If no further studies on the day -
turn everything off except the NO analyser.
o If there is a gap between studies turn off the pressure monitor only to conserye the battery.
r The ozone generator can be switched off overnight but it should be switched on again an
hour before the study to stabilise.
o The NO analyser can be switched off if it is not going to be used for long periods - switch
off the ozone generator I't, then the NO analyser and finally the vacuum pump.
6.5.2 The exhalation protocol
Standard protocol for exhalation is described here and forms the basis for all the subsequent
experiments - any deviation in order to assess different factors is documented in each
experiment.
136