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Problem
Invalid parameters exist in
expiratory-only breath-detect
mode.
Tidal volume errors in expiratory
only mode.
Table C-1. Troubleshooting (cont.)
Possible Cause
BTPS or STPD correction
method on the Analyzer is
different that the method used by
the ventilator manufacturer.
Compliance of breathing circuit
tubing is causing a compressible
volume loss.
The Analyzer is used with
humidified gases. Condensation
on the flow sensors causes a
calibration error on the flow
measurement.
Some parameter values are
always invalid in this mode due
to insufficient information in the
expiratory-only signal.
All parameters are invalid
including base flow.
The Analyzer must be able to
accurately detect base flow for
the parameters to be valid.
Some ventilators servo control
the base flow during the
expiratory period. Because the
Analyzer must assume the base
flow is constant during
expiration, errors result due to
the changing base flow from the
ventilator during the expiratory
phase.
Troubleshooting
Corrective Action
Corrections for BTPS and STPD
may vary among different
ventilator manufactures. The
biggest difference is in the water
vapor volume correction. The
Analyzer uses the setting for
relative humidity and
temperature to determine the
actual volume of water vapor in
the flowing gas. This volume is
subtracted from the total volume
for dry gas corrections. For
saturated gas correction, a
make-up volume of water vapor
is computed and added to the
measured volume.
Determine the breathing circuit
compliance to calculate the
expected volume loss due to
compressibility of the gas and
expansion of the hose.
Run DRY air through the flow
sensor for 10 to 30 minutes to
allow the screen mesh to dry. Do
not use the Analyzer with
condensing humidified gases.
Use the bi-directional breath
detect mode. Ensure the
Analyzer is placed between the
Y of the breathing circuit and a
test lung.
Increase the end-expiratory
period by either changing the I:E
ratio or by decreasing the lung
compliance (higher pressures).
Ensure that the change in airway
pressure during the breath is
greater than 5 cmH2O.
Use the bi-directional breath
detect mode. Ensure that the
Analyzer is placed between the
Y of the breathing circuit and a
test lung.
Appendices
C
C-3
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