The ISO 80601-2-61:2018 standard defines clinical evaluation methods for pulse oximeter devices. Clinical trials are costly, time-intensive, and operationally complex. Because failures at this stage can lead to schedule delays, redesign, or changes to performance claims, it is important to verify device performance before entering clinical evaluation.
Clinical trials are intended to confirm performance, not to uncover fundamental measurement limitations. Therefore, claimed performance characteristics and operating ranges of the device under test should be systematically verified before entering clinical evaluation. Without controlled pre-clinical validation, portions of the device's performance range may remain unverified until downstream stages of development.
According to the ISO 80601-2-61:2018 standard, pulse oximeter devices that generate analog signals are referred to as functional testing instruments. A suitable functional testing instrument helps confirm whether the pulse oximeter device can exhibit the various performance characteristics designed by the manufacturer. These characteristics primarily include the values and ranges of heart rate and blood oxygen saturation.
The standard defines testing principles for transmittance SpO2, and the same principles apply to reflective SpO2 testing. However, the standard does not provide procedures for systematically testing performance characteristics using a functional testing instrument.
In the absence of defined procedural guidance, manufacturers must establish controlled methods to validate performance range, stability, and measurement behavior prior to clinical evaluation. Because human-based testing cannot independently control and reproduce key optical and physiological parameters, a transmittance or reflective functional testing instrument with defined test procedures becomes an valuable validation method for systematic performance testing.
These performance tests should at least include the ability to adjust the perfusion index for red and infrared light, set the R-value, establish an R-curve, and handle heart rate changes. Since the perfusion index is defined as AC/DC * 100%, where AC and DC are the components of transmitted or reflected light, respectively, in a resting state, the AC component represents changes in arterial volume, while the DC component reflects skin color.
From the range of these parameter settings, the pulse oximeter can obtain different R-values and reference R-curves based on simulating individuals with different skin colors and arterial elasticities, thereby simulating a wide range of SpO2 values and testing the SpO2 performance, range, and stability of the pulse oximeter. Changing the frequency of the AC signal can simulate different heart rates, used to test heart rate performance, measurement range, and stability, and can also test whether changes in heart rate affect the stability of SpO2 values.
By enabling independent and precise control of these physiological parameters, systematic verification of SpO2 accuracy, measurement range, and stability can be performed under repeatable conditions before clinical evaluation.
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