MANUAL PHYSIOLOGY PRACTICAL - Repository:The Medical ...

FM/UOJ
The reading can be taken up to three decimal points. Initial reading of the gas
meter has to be taken before allowing the gas to pass through the meter. Next reading will
be taken after the gas has been passed through the meter. Difference between both
readings will give the volume of the gas that has passed through the gas meter, in cubic
meter: multiplying this value by 1000 will give the volume in liters.
Paramagnetic Oxygen Analyzer:
The analyzer operates on the basis of the paramagnetic property of gas to be
analyzed. The gas with paramagnetic property is passed through the analytic cell. The
cell contains a silica dumb-bell suspended in a non-uniform magnetic field. The
paramagnetic property of the gas in the cell causes the dumb-bell to rotate and adapt a
new angle. The analyzer senses the change of position of the dumb-bell by a light ray
reflected by a mirror attached to the dumb-bell. The analyzer sends current through a coil
in the dumb-bell until the dumb-bell assumes its original position, indicated by the light
beam. The current needed to oppose the paramagnetic force of the gas is proportional to
the concentration of the gas.
As oxygen is paramagnetic, it can be measured accurately if there are no other
gases with paramagnetic property. Therefore the gas passing through the cell should be
dry because water vapor is also paramagnetic.
Carbon Dioxide Analyzer:
The analyzer operates on the basis of the ability of carbon dioxide to absorb intra
red rays. The analyzer has two chambers: carbon dioxide free dry air is passed through
one as a standard gas and the gas mixture containing carbon dioxide is passed through the
other. The partition between the two chambers is sensitive to the amount of infra red rays
falling on both surfaces. The rays on one side are absorbed by the carbon dioxide and
therefore the reduction in the amount of rays is proportional to the amount of carbon
dioxide in the chamber. This is used to detect the amount of carbon dioxide in the sample.
Respiration
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