Nonin and Choice Oximeter Review - Pulse Rate, Light and Motion

Under Construction


Nonin and Choice oximeter reivew: This is the fifth in a series of articles in comparing the performance of oximeters made by Nonin and Choice. We used the four oximeters Onyx 9500, MD300C63, GO2, and MD300C1 to take measurements under different pulse rates, light conditions and motion levels. The objective is to test these oximeters under the most extreme situations, including cases that are outside normal operating ranges and would rarely happen in real situations.

Pulse Rate

We started with the following initial conditions and varied the pulse rate from 45 BPM to 180 BPM.

  1. Bradycardia: SpO2 88%, Signal Strength: 5%
  2. Neonate: SpO2 90%, Signal Strength: 1%

The results for all four oximeters are similar and in agreement.

Ambient light conditions

The BIOTEK Index SpO2 Simulator can simulate three different light conditions.

Light Type Frequency Description
Sunlight n/a Index 2XL simulates sunlight by controlling the output from an LED so that a light level is added to the simulation. This light level is present both between, and during, red and infrared pulses.
Artificial 50 Hz Artificial light is simulated by superimposing 50 Hz noise on the pleth wave.
Artificial 60 Hz Artificial light is simulated by superimposing 60 Hz noise on the pleth wave.

Fluorescent lamps can produce flicker at the mains frequency (50 or 60 Hz) and can affect oximeter readings.

All the oximeters under testing did an excellent job in filtering out the ambient noise. There is no or little changes when taking measurements under these settings.


A pulse oximeter has a pair of small light-emitting diodes (LEDs) facing a photodiode through a translucent part of the patient's body, usually a fingertip. These LEDs are at different wavelengths and absorption at these wavelengths differs significantly between oxyhemoglobin and its deoxygenated form. SpO2 is calculated from the ratio of the absorption of the red and infrared light. During a measurement, if the LED and the finger moved relative to each other, the signals would be corrupted or interrupted. This test is to gauge the tolerance of the oximeters to motion.

BIOTEK simulator has two motion levels - "Motion Level 1 is recommended when testing pulse oximeters with Masimo Set technology. Use Motion Level 2 when testing pulse oximeters with Nellcor Motion technology". When we attempted to apply these two motion levels to the oximeters, we could not provide reliable data. No conclusive result can be obtained. Our general impression was that the Nonin oximeters were somewhat more tolerant to motion than the Choice oximeters.