A prototype device for standardized calibration of pulse oximeters

Objective. To develop and test a method for standardized calibration of pul se oximeters. Methods. A novel pulse oximeter calibration technique capable of simulating the behavior of real patients is discussed. It is based on a n artificial finger with a variable spectral-resolved light attenuator in c onjunction with an extensive clinical database of time-resolved optical tra nsmission spectra of patients fingers in the wavelength range 600-1000 nm. The arterial oxygen saturation of the patients at the time of recording was derived by analyzing a corresponding blood sample with a CO-oximeter. Thes e spectra are used to compute the modulation of the light attenuator which is attached to the artificial finger. This calibration method was tested by arbitrarily playing back recorded spectra to pulse oximeters and comparing their display to the value they displayed when the spectra were recorded. Results. We were able to demonstrate that the calibrator could generate phy siological signals which are accepted by a pulse oximeter. We also present some experience of playing back recorded patient spectra. The mean differen ce between the original reading of the pulse oximeters and the display when attached to the calibrator is 1.2 saturation points (displayed oxygen satu ration SpO(2)) with a standard deviation of 1.9 saturation points. Conclusi ons. The tests have shown the capabilities of a spectral light modulator fo r use as a possible calibration standard for pulse oximeters. If some impro vements of the current prototype can be achieved we conclude from the exper ience with the device that this novel concept for the calibration of pulse oximeters is feasible and that it could become an important tool for assess ing the performance of pulse oximeters.