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Chapter 7: Spirometry Technique
DATOSPIR MICRO User’s Manual 202
511-A00-MU2 • REV. 2.06
although at least one of the elements of the biological signal, the
volume or the flow, must be reproduced together or separately.
Along these lines, the syringes holding several litres provide a
suitable signal and the flow generators can be used to assess
the precision and errors in flow measurement. Among the
most suitable calibration appliances is the so-called explosive
decompressor, which consists of a 4 or 5-litre pressurised, one-
atmosphere chamber fitted with a fast opening for the sudden
expulsion of an identical volume to that of the chamber. This
simulates the forced expiration of a person and, with suitable
resistances at different levels of obstruction fitted to the output
tube, the signal is similar to that of a patient with slight, moderate
or severe obstruction in the air flow. Hence, the volume and
flow measurement can be examined. If this is not possible, the
working order of the appliance must be checked using «control
individuals». i.e. people close to the laboratory and whose
cooperation is attainable, to carry out correct spirometry with
easy and scarce variability (Table I), so that their spirometry can
be regularly reproduced and compared with the previous data.
Hence, errors can be detected that would have to be significant
in size, as the variability of spirometry itself prevents small
differences in the measuring of volume and flow from being
detected (see Table I).”
“Under normal working conditions, calibration using the volume
signal provided by a manual syringe will be performed on a daily
basis. The signal provided by the syringe must be produced
with different pulses to check whether the flow reading remains
steady, as the appliance must always integrate the signal in the
same volume - that provided by the syringe signal - whatever
the suddenness of the injection manoeuvre, with the upper limit
of the flow range precisely measured (close to the real value) by
the instrument in question not being exceeded. Calibration with
a dynamic signal produced by the explosive decompressor or the
measuring of spirometry on control individuals, as mentioned
above, may be performed relatively less often. It is wise to
perform calibration using the decompressor every fortnight in the
case of pneumotachometers. Given that spirometry with control