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Background Millions of smartphones contain a photoplethysmography (PPG) bio-sensor (Maxim Integrated, San Jose CA) that accurately measures pulse oximetry. No clinical use of these embedded sensors is currently being made, despite the relevance of remote clinical pulse oximetry to the management of chronic cardiopulmonary disease, and the triage, initial management and remote monitoring of persons effected by respiratory viral pandemics, such as SARS-CoV-2 or Influenza. To be used for clinical pulse oximetry the embedded PPG system must be paired with an App and meet FDA and ISO requirements. Research Question We evaluated whether this smartphone sensor with App met FDA/ISO requirements and how measurements obtained using this system compared to hospital reference devices across a wide range of persons. Study Design and Methods We performed laboratory testing addressing ISO and FDA requirements in ten participants using the smartphone sensor with App. Subsequently, we performed an open label clinical study on 320 participants with widely varying characteristics, to compare accuracy and precision of readings obtained by patients, to hospital reference devices using a rigorous statistical methodology. Results ‘Breathe Down’ testing in the laboratory showed that the total Root Mean Square Deviation (RSMD) of SpO 2 measurement was 2.02%, meeting FDA/ISO standards. Clinical comparison of the smartphone sensor with App versus hospital reference devices determined SpO 2 and heart rate (HR) accuracy was 0.48 % points (CI 0.38 to 0.58; p<0.001) and 0.73 bpm (CI 0.33 to 1.14; p<0.001) respectively; with SpO 2 and HR precision 1.25 versus reference 0.95 points (p< 0.001) and 5.99 versus reference 3.80 bpm (p<0.001), respectively. These small differences were similar to the variation found between two FDA approved reference instruments for SpO 2 : accuracy 0.52 points (CI 0.41 to 0.64; p<0.001) and precision 1.01 versus 0.86 (p<0.001). Interpretation Our findings support the application for full FDA/ISO approval of the smartphone sensor with App tested for use in clinical pulse oximetry. Given the immense and immediate practical medical importance of remote intermittent clinical pulse oximetry to both chronic disease management and the global ability to respond to respiratory viral pandemics, the smartphone sensor with APP should be prioritized and fast tracked for FDA/ ISO approval to allow clinical use.

Abstract.Hypoxemia measured by pulse oximetry predicts child pneumonia mortality in low-resource settings (LRS). Existing pediatric oximeter probes are prohibitively expensive and/or difficult to use, limiting LRS implementation. Using a human-centered design, we developed a low-cost, reusable pediatric oximeter probe for LRS health-care workers (HCWs). Here, we report probe usability testing. Fifty-one HCWs from Malawi, Bangladesh, and the United Kingdom participated, and seven experts provided reference measurements. Health-care workers and experts measured the peripheral arterial oxyhemoglobin saturation (SpO2) independently in < 5 year olds. Health-care worker measurements were classed as successful if recorded in 5 minutes (or shorter) and physiologically appropriate for the child, using expert measurements as the reference. All expert measurements were considered successful if obtained in < 5 minutes. We analyzed the proportion of successful SpO2 measurements obtained in < 1, < 2, and < 5 minutes and used multivariable logistic regression to predict < 1 minute successful measurements. We conducted four testing rounds with probe modifications between rounds, and obtained 1,307 SpO2 readings. Overall, 67% (876) of measurements were successful and achieved in < 1 minute, 81% (1,059) < 2 minutes, and 90% (1,181) < 5 minutes. Compared with neonates, increasing age (infant adjusted odds ratio [aOR]; 1.87, 95% confidence interval [CI]: 1.16, 3.02; toddler aOR: 4.33, 95% CI: 2.36, 7.97; child aOR; 3.90, 95% CI: 1.73, 8.81) and being asleep versus being calm (aOR; 3.53, 95% CI: 1.89, 6.58), were associated with < 1 minute successful measurements. In conclusion, we designed a novel, reusable pediatric oximetry probe that was effectively used by LRS HCWs on children. This probe may be suitable for LRS implementation.

Objective To assess the performance of reusable pulse oximeter probe and microprocessor box combinations, of varying price‐points, in the context of a low‐income pediatric setting. Methods A prospective, randomized cross‐over study comparing time to biologically plausible oxygen saturation (SpO2) between: (1) Lifebox LB‐01 probe with Masimo Rad‐87 box (L + M) and (2) a weight‐appropriate reusable Masimo probe with Masimo Rad‐87 box (M + M). A post hoc secondary analysis comparison with historical usability testing data with the Lifebox LB‐01 probe and Lifebox V1.5 box (L + L) was also conducted. Participants, children aged 0 to 35 months, were recruited from pediatric wards and outpatient clinics in the central region of Malawi. The primary outcome was time taken to achieve a biologically plausible SpO 2 measurement, compared using t tests for equivalence. Results We recruited 572 children. Plausible SpO2 measurements were obtained in less than 1 minute, 71%, 70%, and 63% for the M + M, L + M, and L + L combinations, respectively. A similar pattern was seen for less than 2 minutes, however, this effect disappeared at less than 5 minutes with 96%, 96%, and 95% plausible measurements. Using a ±10 second threshold for equivalence, we found L + M and M + M to be equivalent, but were under‐powered to assess equivalence for L + L. Conclusions The novel reusable pediatric Lifebox probe can achieve a quality SpO2 measurement within a pragmatic time range of weight‐appropriate Masimo equivalent probes. Further research, which considers the cost of the devices, is needed to assess the added value of sophisticated motion tolerance software.

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. 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. 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 oxygen saturation (SaO2) 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 SaO2 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 (SpO2) 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 SpO2 measurements to support at home assessment of COVID-19 patients.