Page 9
.
Intended Use, Principles of Operation and Limitations
SenTec TC Sensors
SenTec TC Sensors provide superior performance, are robust,
reliable and require comparatively low maintenance. They
combine within a patented digital sensor design the optical
components needed for 2-wavelength, reflectance pulse
oximetry with the components needed to measure PCO
2
and –
in case of the OxiVenT™ Sensor only – PO
2
.
PO
2
(OxiVenT™ Sensor) is measured with dynamic fluorescence
quenching, an oxygen sensing technology measuring the
oxygen molecules present in the vicinity of a fluorescent dye
being immobilized in a thin carrying layer incorporated within
the sensor surface.
The PCO
2
measurement of SenTec TC Sensors (V-Sign™
Sensor 2, OxiVenT™ Sensor) is based on a Stow-Severinghaus
type PCO
2
sensor, i.e. a thin electrolyte layer is confined to
the sensor surface with a hydrophobic, CO
2
and O
2
permeable
membrane. Membrane and electrolyte must be exchanged
every 28 to 42 days. With SenTec’s patented Membrane
Changer the membrane and electrolyte can be changed
with the ease of 4 identical Press-and-Turn steps in a highly
reproducible manner (p.
17
).
Calibration of the PCO
2
segment of SenTec TC Sensors is
recommended every 6 to 12 hours and mandatory every 12 to
16 hours (p.
16
). The PO
2
measurement of the OxiVenT™
Sensor is virtually drift free and, hence, calibration free.
Nevertheless, the SDM, as a precaution, calibrates PO
2
during
each mandatory calibration and subsequently approximately
once every 24 hours during one of the anyways ongoing PCO
2
calibrations.
To achieve local arterialization of the skin tissue at the
measurement site, SenTec TC Sensors are operated at a
constant sensor temperature of typically 41 °C in neonatal and
42 °C in adult/pediatric patients if PO
2
is disabled and – if PO
2
is enabled – of typically 43 °C in neonatal and 44 °C in adult/
pediatric patients, respectively. Controls of sensor temperature
and application duration are designed to meet all applicable
standards. To guarantee safe operation, SenTec TC Sensors
reliably supervise the sensor temperature with two independent
circuits. Additionally, the SDM firmware redundantly controls
the temperature of the connected sensor.
