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Deviations between measurements from different SpO2 sensors

Article

Author: Simon Franz

Date of first publication: 16.02.2018

How is it possible that my patient monitoring system shows a different value for the saturation of peripheral oxygen (SpO2) than the Hamilton Medical ventilator?

Deviations between measurements from different SpO2 sensors

Accuracy of sensors ±3%

The accuracy of pulse oximetry SpO2 measurements depends on the SpO2 range, patient motion and perfusion. The accuracy of sensors from different manufacturers is typically around ±3% for SpO2 values of > 90% (see Figure 1) (Milner QJ, Mathews GR. An assessment of the accuracy of pulse oximeters. Anaesthesia. 2012;67(4):396-401. doi:10.1111/j.1365-2044.2011.07021.x1​).

Therefore, it is possible to have different SpO2 values when using multiple sensors even if using two sensors with the same technology.

 

Grahps showing bias at different values
Figure 1: The bias of 758 pulse oximeter sensors at different SpO2 values: (a) 97%, (b) 90%, (c) 80%, (d) 70%
Grahps showing bias at different values
Figure 1: The bias of 758 pulse oximeter sensors at different SpO2 values: (a) 97%, (b) 90%, (c) 80%, (d) 70%

If you are using SpO2 measurement in a Hamilton Medical ventilator with the INTELLiVENT®-ASV® (Not available in the US and some other marketsA​) oxygenation controller and see constant deviations between your patient monitoring and ventilator SpO2 values, you should perform an arterial blood gas analysis to check the SpO2 against arterial oxygen saturation (SaO2).

If there is a constant difference between the SpO2 and SaO2 values, an SpO2 target shift can be used.

As stated in the INTELLiVENT-ASV Operator’s Manual, additional ventilator-independent patient monitoring (for example, bedside vital monitoring or a blood gas analyzer) must be used during ventilation with INTELLiVENT-ASV.

Relevant devices (for SpO2 measurement option (Standard on the HAMILTON-S1B​)): all excluding HAMILTON-MR1

Footnotes

  • A. Not available in the US and some other markets
  • B. Standard on the HAMILTON-S1

References

  1. 1. Milner QJ, Mathews GR. An assessment of the accuracy of pulse oximeters. Anaesthesia. 2012;67(4):396-401. doi:10.1111/j.1365-2044.2011.07021.x

An assessment of the accuracy of pulse oximeters.

Milner QJ, Mathews GR. An assessment of the accuracy of pulse oximeters. Anaesthesia. 2012;67(4):396-401. doi:10.1111/j.1365-2044.2011.07021.x

Peripheral pulse oximetry has become a core monitoring modality in most fields of medicine. Pulse oximeters are used ubiquitously in operating theatres, hospital wards, outpatient clinics and general practice surgeries. This study used a portable spectrometer (Lightman(®), The Electrode Co. Ltd., Monmouthshire, UK) to measure the emission spectra of the two light emitting diodes within the pulse oximeter sensor and to determine the accuracy of 847 pulse oximeters currently in use in 29 NHS hospitals in the UK. The standard manufacturing claim of accuracy for pulse oximeters is ± 2-3% over the range of 70-100% S(p)O(2). Eighty-nine sensors (10.5%) were found to have a functional error of their electrical circuitry that could cause inaccuracy of measurement. Of the remaining 758 sensors, 169 (22.3%) were found to have emission spectra different from the manufacturers' specification that would cause an inaccuracy in saturation estimation of > 4% in the range of 70-100% saturation. This study has demonstrated that a significant proportion of pulse oximeter sensors may be inaccurate.

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