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Nellcor SpO2 Sensors
58 Portable Bedside Capnograph/Pulse Oximeter
Data Update Period, Data Averaging, and Signal Processing
The advanced signal processing of the OxiMax™ algorithm automatically extends the amount of data required
for measuring SpO
2
and pulse rate depending on the measurement conditions. The OxiMax™ algorithm
automatically extends the dynamic averaging time required beyond seven (7) seconds during degraded or
difficult measurement conditions caused by low perfusion, signal artifact, ambient light, electrocautery, other
interference, or a combination of these factors, which results in an increase in the dynamic averaging. If the
resulting dynamic averaging time exceeds 20 seconds for SpO
2
, the algorithm sets the pulse search bit while
continuing to update SpO
2
and pulse rate values every second.
As such measurement conditions extend, the amount of data required may continue to increase. If the dynamic
averaging time reaches 40 seconds, and/or 50 seconds for pulse rate, a technical alarm state results: the
algorithm sets the Pulse Timeout bit and the monitoring system reports a zero saturation indicating a loss-of-
pulse condition, which should result in an audible alarm.
Functional Testers and Patient Simulators
Some models of commercially available bench top functional testers and patient simulators can be used to verify
the proper functionality of Covidien Nellcor™ monitoring systems, sensors, and cables. Reference the
individual testing device's operator's manual for the procedures specific to the model of tester used. While such
devices may be useful for verifying that the sensor, cabling, and monitoring system are functional, they are
incapable of providing the data required to properly evaluate the accuracy of a system's SpO
2
measurements.
Fully evaluating the accuracy of the SpO
2
measurements requires, at a minimum, accommodating the
wavelength characteristics of the sensor and reproducing the complex optical interaction of the sensor and the
patient’s tissue. These capabilities are beyond the scope of known bench top testers. SpO
2
measurement
accuracy can only be evaluated in vivo by comparing monitoring system readings with values traceable to SaO
2
measurements obtained from simultaneously sampled arterial blood using a laboratory CO-oximeter.
Many functional testers and patient simulators have been designed to inter-face with the monitoring system's
expected calibration curves and may be suitable for use with monitoring systems and/or sensors. Not all such
devices, however, are adapted for use with the OxiMax™ digital calibration system. While this will not affect
use of the simulator for verifying system functionality, displayed SpO
2
measurement values may differ from the
setting of the test device. For a properly functioning monitoring system, this difference will be reproducible
over time and from monitoring system to monitoring system within the performance specifications of the test
device.
Selecting Nellcor SpO
2
Sensors
When selecting a sensor, consider the patient's weight and activity, the adequacy of perfusion, the available
sensor sites, and the anticipated duration of monitoring. The sensor models are summarized in
Table 11 -
Nellcor SpO2 Sensors , below. For further information, please contact your local representative.
Nellcor pulse oximetry sensors contain light emitting diodes (LEDs) that emit red light at a wavelength of
approximately 660 nm, and infrared light at a wavelength of approximately 900 nm. The total optical output
power of the sensor LEDs is less than 15 mW. This information may be useful to clinicians, such as those
performing photodynamic therapy.
Table 11 - Nellcor SpO
2
Sensors
Oxygen Sensor Model Patient Weight
O
XI
M
AX
®
oxygen transducer
(single patient use)
MAX-N <3 kg or >40 kg
MAX-I 3 to 20 kg
MAX-P 10 to 50 kg
MAX-A >30 kg
MAX-AL >30 kg
MAX-R >50 kg