Accuracy of Samsung Smartphone Integrated Pulse Oximetry Meets Full FDA Clearance Standards for Clinical Use

  1. Sara H. Browne
  2. Mike Bernstein
  3. Philip E. Bickler

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Abstract

Background

Pulse oximetry is used as an assessment tool to gauge the severity of COVID-19 infection and identify patients at risk of poor outcomes. 1,2,3,4 The pandemic highlights the need for accurate pulse oximetry, particularly at home, as infection rates increase in multiple global regions including the UK, USA and South Africa 5 . Over 100 million Samsung smartphones containing dedicated biosensors (Maxim Integrated Inc, San Jose, CA) and preloaded Apps to perform pulse oximetry, are in use globally. We performed detailed in human hypoxia testing on the Samsung S9 smartphone to determine if this integrated hardware meets full FDA/ISO requirements for clinical pulse oximetry.

Methods

The accuracy of integrated pulse oximetry in the Samsung 9 smartphone during stable arterial oxygen saturations (SaO 2 ) between 70% and 100% was evaluated in 12 healthy subjects. Inspired oxygen, nitrogen, and carbon dioxide partial pressures were monitored and adjusted via a partial rebreathing circuit to achieve stable target SaO 2 plateaus between 70% and 100%. Arterial blood samples were taken at each plateau and saturation measured on each blood sample using ABL-90FLEX blood gas analyzer. Bias, calculated from smartphone readings minus the corresponding arterial blood sample, was reported as root mean square deviation (RMSD).

Findings

The RMSD of the over 257 data points based on blood sample analysis obtained from 12 human volunteers tested was 2.6%.

Interpretation

Evaluation of the smartphone pulse oximeter performance is within requirements of <3.5% RMSD blood oxygen saturation (SpO 2 ) value for FDA/ISO clearance for clinical pulse oximetry. This is the first report of smartphone derived pulse oximetry measurements that meet full FDA/ISO accuracy certification requirements. Both Samsung S9 and S10 contain the same integrated pulse oximeter, thus over 100 million smartphones in current global circulation could be used to obtain clinically accurate spot SpO 2 measurements to support at home assessment of COVID-19 patients.

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    SciScore for 10.1101/2021.02.17.21249755: (What is this?)

    Please note, not all rigor criteria are appropriate for all manuscripts.

    Table 1: Rigor

    Institutional Review Board StatementIRB: The work was sanctioned by the UCSF Committee on Human Research, protocol 10-00437, and conformed to all internationally accepted standards for the protection of human subjects.
    Consent: All volunteers provided written informed consent.
    Randomizationnot detected.
    Blindingnot detected.
    Power Analysisnot detected.
    Sex as a biological variableWe enrolled 12 participants, 4 male, 8 female, including 3 participants with darkly pigmented skin.

    Table 2: Resources

    No key resources detected.

    Results from OddPub: We did not detect open data. We also did not detect open code. Researchers are encouraged to share open data when possible (see Nature blog).

    Results from LimitationRecognizer: We detected the following sentences addressing limitations in the study:
    Aside from these limitations, the major determinant of accuracy differences observed across these studies likely reflects differences in the quality of the underlying hardware and proprietary algorithms within the smartphone tested. Whilst traditional pulse oximeters in hospital settings rely on the transmission of light through cutaneous tissues such as the finger or ear lobe, smartphones systems utilize reflected light detected by a sensor on the same surface as the emitter. 25 Within such systems how the reflected light signal is obtained and analyzed is critical. Poorly performing pulse oximetry Apps used the onboard light and camera lens to obtain reflected light to detect PPG signals and conformational changes associated with hemoglobin binding. Signal obtained from camera associated sensors have relatively high signal to noise ratios and may even block near infrared light. 25 In contrast, the smartphone evaluated in our study has dedicated hardware specifically for pulse oximetry function (see Figure 1) with 660nM red and 910nM infrared LEDs used to take measurements, a photodetector connected to an extremely low noise analog channel allowing measurement on a broad range of skin colors, and placement entirely separate from other phone devices such as the camera. Studies testing similar hardware and algorithms reported high SpO2 measurement accuracy. 24, 22 All future studies evaluating smartphone oximetry accuracy should specify the type of embedded hardware including ...

    Results from TrialIdentifier: No clinical trial numbers were referenced.

    Results from Barzooka: We did not find any issues relating to the usage of bar graphs.

    Results from JetFighter: We did not find any issues relating to colormaps.

    Results from rtransparent:
    • Thank you for including a conflict of interest statement. Authors are encouraged to include this statement when submitting to a journal.
    • Thank you for including a funding statement. Authors are encouraged to include this statement when submitting to a journal.
    • No protocol registration statement was detected.

    About SciScore

    SciScore is an automated tool that is designed to assist expert reviewers by finding and presenting formulaic information scattered throughout a paper in a standard, easy to digest format. SciScore checks for the presence and correctness of RRIDs (research resource identifiers), and for rigor criteria such as sex and investigator blinding. For details on the theoretical underpinning of rigor criteria and the tools shown here, including references cited, please follow this link.

  2. Version published to 10.1101/2021.02.17.21249755v1 on medRxiv