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The Use of Pulse Oximeter Functional Testers in Evaluating Spo2 Accuracy

Mannheimer, Paul D. PhD; Batchelder, Paul B. RRT; Larsen, Mike; Gehring, Hartmut MD; Konecny, Ewald PhD

doi: 10.1213/01.ANE.0000137450.24266.00
Letters to the Editor: Letters & Announcements
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Principal Scientist; Research and Development Department; Nellcor Puritan Bennett, a part of Tyco Healthcare; Pleasanton, CA; paul.mannheimer@tycohealthcare.com (Mannheimer)

Head of Clinical Research; Pulse Oximetry Center of Excellence; Datex-Ohmeda, GE Medical Systems; Boulder, CO (Batchelder)

Vice President - Quality; Criticare Systems, Inc.; Waukesha, WI (Larsen)

Professor of Anesthesiology; Department of Anesthesiology; University of Lübeck; Lübeck, Germany (Gehring)

Professor Emeritus; Institute of Biomedical Engineering; University of Lübeck; Lübeck, Germany (Konecny)

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To the Editor:

We read with interest the study of pulse oximeter probes (1), but must take exception to the study’s methodology and conclusions. The study was intended to evaluate and compare the accuracy of prototype nonproprietary probes (OSS/Dolphin Medical) to their counterpart proprietary sensors from the original equipment manufacturers (Nellcor, Datex-Ohmeda, and Criticare). The protocol used a bench-top patient simulator (BioTek Index) to compare the various sensors’ pulse oximeter Spo2 readings with the simulator set points. The study’s conclusions suggest equivalence or superiority of performance in nonproprietary probes.

Unfortunately, the authors have grossly misinterpreted the ability of this simulator to evaluate the probe’s contribution to Spo2 reading accuracy. While the Index and several other commercially available patient simulators can test sensor and pulse oximeter functionality, they are incapable of providing the required data needed to properly evaluate the accuracy of Spo2 readings (according to a letter to Nellcor Puritan Bennett from Peter M. Weith, BioTek Instruments, October 1995). With respect to pulse oximeter probes, the patient simulator used in the study is capable only of “testing for shorts, continuity, opens and LED functionality” (2). Evaluating Spo2 reading accuracy would require, at a minimum, accommodating the wavelength characteristics of the sensor and reproducing the complex optical interaction of the sensor and the patient’s tissue.

There are no bench-top simulators available today that can provide the data the authors would need to support their conclusion. The ASTM and ISO Committees for developing pulse oximetry standards have recognized the issue of bench-top accuracy testing (3), and an effort supported by the European Union to create such a device is currently underway (4,5). We are aware of only one validated method to assess Spo2 reading accuracy—direct comparison to sampled arterial blood Sao2 measured using a laboratory co-oximeter.

We therefore disagree with the authors’ two conclusions; their study demonstrates neither equivalency of the nonproprietary probes, nor that a simulator can be used to evaluate pulse oximetry probe accuracy.

Paul D. Mannheimer, PhD

Principal Scientist

Research and Development Department

Nellcor Puritan Bennett, a part of Tyco Healthcare

Pleasanton, CA

paul.mannheimer@tycohealthcare.com

Paul B. Batchelder, RRT

Head of Clinical Research

Pulse Oximetry Center of Excellence

Datex-Ohmeda, GE Medical Systems

Boulder, CO

Mike Larsen

Vice President - Quality

Criticare Systems, Inc.

Waukesha, WI

Hartmut Gehring, MD

Professor of Anesthesiology

Department of Anesthesiology

University of Lübeck

Lübeck, Germany

Ewald Konecny, PhD

Professor Emeritus

Institute of Biomedical Engineering

University of Lübeck

Lübeck, Germany

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References

1. van Oostrom JH, Melker RJ. Comparative testing of pulse oximeter probes. Anesth Analg 2004;98:1354–8.
2. BioTek Instruments FDA 510(k) K971273. Available at www.fda.gov/cdrh/pdf/k971273.pdf. Accessed May 2004.
3. International Organization for Standardization (ISO). Simulators, calibrators and functional testers for pulse oximeter equipment. ISO TC 121/SC 3, Draft International Standard 9919, Annex FF, 2003.
4. Hornberger C, Knoop P, Nahm W, et al. A prototype device for standardized calibration of pulse oximeters. J Clin Monit 2000;16:161–9.
5. Hornberger C, Knoop P, Matz H, et al. A prototype device for standardized calibration of pulse oximeters II. J Clin Monit 2002;17: 203–9
© 2004 International Anesthesia Research Society