Larsen & Toubro Star 55, Operating Manual

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from pulmonary blood to alveolar gas space. CO
2
diffuses into this space because
continuous breathing keeps CO
2
concentration in alveoli lower than that in
pulmonary circulation. During exhalation, gas leaving lungs mixes thoroughly,
so Capnograph measures average concentration of CO
2
from all the alveoli.
Capnography gives an excellent pictures of respiratory process.
Arterial to alveolar difference of CO
2
Although end tidal CO
2
closely follows blood CO
2
level, they are not exactly
same, Normally, the arterial blood CO
2
level (PaCO
2
) is higher by 3-4 mmHg.
than the alveolar CO
2
(PACO
2
). The aADCO
2
is due to a mismatch of ventilation
and perfusion of the alveoli in the lungs. (Even in healthy patient, there are
some part of lungs which are not perfused as well as they are ventilated). In
such case when patient exhales, CO
2
gas from the unperfused part of the lungs
will dilute the CO
2
rich alveolar gas coming from rest of the lungs, lowering the
EtCO
2
, hence aADCO
2
increases. This is known as alveolar dead space ventilation.
Arterial Blood CO
2
: PaCO
2
Alveolar CO
2
: PACO
2
Arterial to alveolar difference aADCO
2
which is normally 3-4 mmHg.
Technology Used
Capnography measurement is done with the help of microstream technology
in this unit.
Microstream Capnography
In microstream capnography method, the optical sensor is incorporated in
the module. Gas sample is aspirated from the patient at a flow rate of 50
ml/min with the help of FilterLine (connected to endotrachial tube with the
help of ‘T’ connector or directly from nose with the help of Nasal prongs)
and is given to module. The CO
2
measurement takes place at the CO
2
bench.
After the measurement, the waste gas exhausted from the rear panel.
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