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wanted to compare the patterns of exhaled NO with COz, the latter being largely of alveolar
origin. For this purpose, I elected to measure expiratory COz, flow and pressure in addition to
the expiratory NO levels which meant developing a number of monitors connected in parallel
that could operate simultaneously. The equipment used, as described below, was all
equipment that was able to be 'seconded' from the adult lung function laboratory and put
together by myself and one of the biomedical engineers (Ms Carolyn Busst, see below) and
the ultimate format is demonstrated in Figure 5.1.
Figure 5.1: Schematic diagram of how the analysers were placed
This is a schematic diagram of the analysers and connections required to measure nitric oxide, carbon
dioxide, mouth pressure and flow. The signals from each of the 4 machines went directly to, and were
displayed on, a Linseis 4 channel pen chart recorder (Linseis Limited, Cambridge, United Kingdom)
with each signal denoted by a different colour.
The COz levels were measured with a Morgan Capnograph (PK Morgan, Kent, United
Kingdom) which sampled at2O0 mls/min-I. Calibration of COz was done using ^zero and gas
cylinder of known COz concentration at 5.9Vo and later 5.7Vo also provided by BOC gases
(address given above). The mouth pressure was measured using a Medex Straingauge
pressure transducer (Medex Medical Incorporated, Rossendale, United Kingdom) which was
connected at right angles to the flow via a connector in the mouthpiece. This was then
directed through a Galtec pressure amplifier (Galtec Limited, Isle of Skye, United Kingdom)
which measured the pressure in mmHg and showed a linear and stable response. The flow
was measured via a flow meter to a low flow pneumotachograph (CT Platon Limited, Jays
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