Validation of a portable, deployablesystem for continuous vital signmonitoring using a multiparametricwearable sensor and personalisedanalytics in an Ebola treatment centre

Steven R Steinhubl,1 Dawit Feye,2 Adam C Levine,3 Chad Conkright,4

Stephan W Wegerich,4 Gary Conkright4

To cite: Steinhubl SR,Feye D, Levine AC, et al.Validation of a portable,deployable system forcontinuous vital signmonitoring using amultiparametric wearablesensor and personalisedanalytics in an Ebolatreatment centre. BMJ GlobalHealth 2016;1:e000070.doi:10.1136/bmjgh-2016-000070

▸ Additional material ispublished online only. Toview please visit the journalonline (http://dx.doi.org/10.1136/bmjgh-2016-000070).

Received 21 April 2016Revised 9 June 2016Accepted 13 June 2016

1Scripps TranslationalScience Institute, La Jolla,California, USA2International Medical CorpsEbola Treatment Center,Makeni, Sierra Leone3International Medical Corps,Washington, DC, USA4physIQ, Chicago, Illinois,USA

Correspondence toDr Steven R Steinhubl;steinhub@scripps.edu

ABSTRACTBackground: The recent Ebola epidemic in WestAfrica strained existing healthcare systems wellbeyond their capacities due to the extreme volumeand severity of illness of the patients. Theimplementation of innovative digital technologieswithin available care centres could potentially improvepatient care as well as healthcare worker safety andeffectiveness.Methods: We developed a Modular Wireless PatientMonitoring System (MWPMS) and conducted a proofof concept study in an Ebola treatment centre (ETC)in Makeni, Sierra Leone. The system was built arounda wireless, multiparametric ‘band-aid’ patch sensorfor continuous vital sign monitoring andtransmission, plus sophisticated data analytics.Results were used to develop personalised analyticsto support automated alerting of early changes inpatient status.Results: During the 3-week study period, all eligiblepatients (n=26) admitted to the ETC were enrolled inthe study, generating a total of 1838 hours ofcontinuous vital sign data (mean of 67.8 hours/patient), including heart rate, heart rate variability,activity, respiratory rate, pulse transit time (inverselyrelated to blood pressure), uncalibrated skintemperature and posture. All patients tolerated thepatch sensor without problems. Manually determinedand automated vital signs were well correlated.Algorithm-generated Multivariate Change Index, pulsetransit time and arrhythmia burden demonstratedencouraging preliminary findings of importantphysiological changes, as did ECG waveform changes.Conclusions: In this proof of concept study, we wereable to demonstrate that a portable, deployablesystem for continuous vital sign monitoring via awireless, wearable sensor supported by asophisticated, personalised analytics platform canprovide high-acuity monitoring with a continuous,objective measure of physiological status of allpatients that is achievable in virtually any healthcaresetting, anywhere in the world.

INTRODUCTIONHealthcare workers in low-income andmiddle-income regions of the world are ascarce resource.1 This chronic shortage is

Key questions

What is already known about this topic?▸ A key challenge to effective patient management

in low-resource settings, and especially duringthe time of a healthcare crisis such as the recentEbola epidemic in West Africa, is lack of suffi-cient healthcare workers and the resourcesnecessary to provide for effective patient moni-toring and tracking.

▸ In Ebola treatment centres, tracking patient vitalsigns is labour intensive and physically challengingdue to the need to wear personal protective equip-ment leading to infrequent monitoring, exposurerisk and inefficient use of limited manpower.

What are the new findings?▸ We demonstrate that a portable, deployable

system for continuous vital sign monitoring viaa wireless, wearable sensor supported by asophisticated, personalised analytics platformcan provide high-acuity monitoring with a con-tinuous, objective measure of physiologicalstatus in a remote setting.

▸ Algorithm-generated parameters through an ana-lytic platform show promise for enhancing indi-vidualised alerting and management capabilities.

Recommendations for policy▸ The system evaluated offers the ability to

provide intensive monitoring and alerting cap-ability in any healthcare setting virtually any-where in the world that following furthervalidation could significantly improve patientoutcomes while extending healthcare workerefficiency and safety.

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further compounded in the setting of a healthcare crisisthat creates a marked increase in demand for healthcareservices in a high-acuity, critical care setting where higherlevels of staffing and resources are required to provideadequate care.2 The recent Ebola virus disease (EVD) epi-demic in West Africa strained existing local healthcaresystems well beyond their capacities due to the extremevolume and severity of illness of the patients, leading toan unprecedented humanitarian tragedy.3 Doubly tragicwas the devastating toll taken on the disproportionatelyaffected healthcare workers caring for patients with EVD.4

Over the past decade, there have been remarkableadvances in digital communication capabilities thatcould potentially help address many of the challengescreated through a lack of healthcare resources. Forexample, over the past decade, the rapid proliferation ofcellular networks throughout sub-Saharan Africa hasenabled a rapid jump to the digital age while foregoingthe need for landlines and their associated infrastruc-ture. Nonetheless, many healthcare facilities in ruralareas in Africa and elsewhere in the world lack thedigital infrastructure necessary to take full advantage ofnew technologies. Therefore, to supplement the ever-expanding wireless infrastructure, the ability to transportand deploy a local wireless infrastructure provides world-wide ability to take advantage of a host of innovativemedical-grade mobile health (mHealth) devices nowavailable that enable the implementation of novel solu-tions for critical gaps in care, especially, but not only, intimes of crisis.5

The recent EVD epidemic in West Africa created asituation especially in need of novel solutions: thenumber and acuity of patients overwhelmed availablehealthcare resources, the intensive monitoring capabil-ities necessary to optimally care for critically ill indivi-duals were scarce, and the high transmissibility of thevirus required personal protective equipment (PPE) usethat significantly impacted the time and ability of health-care providers to interact with patients. In order toaddress some of these enormous challenges, we devel-oped a Modular Wireless Patient Monitoring System(MWPMS) and conducted a proof of concept study,through the support of the Ebola Grand Challenge, tovalidate a novel system of care in an Ebola treatmentcentre (ETC). The MWPMS was built around a wireless,multiparametric ‘band-aid’ sensor for continuous vitalsign monitoring and transmission, plus a sophisticateddata analytic platform in order to develop personalisedpredictive analytics to support automated alerting ofearly changes in patient status and allow for the betterinformed triaging of scarce resources. The ultimate goalof the MWPMS is to allow for improved, automatedpatient oversight, enabling increased timeliness of carefor acutely ill individuals. Simultaneously, it will improvehealthcare worker safety and productivity by minimisingunnecessary exposure risks and allowing them to con-centrate on care activities that truly require a humantouch.

METHODSFunding for this study was provided through ‘FightingEbola: A Grand Challenge for Development’, launchedby the US Agency for International Development(USAID) in partnership with the White House Office ofScience and Technology, the Centers for Disease Controland Prevention, and the Department of Defense. It wascarried out in collaboration with the humanitarian organ-isation International Medical Corps.

ETC—Makeni, Sierra LeoneAn ETC opened outside Makeni, Sierra Leone inDecember 2014, funded by the UK’s Department forInternational Development and run by InternationalMedical Corps was the site of this study6 (see onlinesupplementary figure S1). It was a 50-bed facility that pro-vided care 24/7 by national and international workers dis-tributed into three primary teams based on principalresponsibilities: Medical, Water, Hygiene and Sanitation(WASH) and Psychosocial.Individuals suspected of potentially having Ebola based

on their contact history, presence of a fever, signs of easybleeding and systemic symptoms were transferred to theETC and evaluated in a triage zone for admission.Individuals meeting admission criteria, who were aged18 years or older, were able to understand the informedconsent, and without a prior history of skin sensitivity toadhesives, were approached for enrolment and informedconsent was obtained. The informed consent documentwas written in English, the official language of SierraLeone; however, for the majority of individuals, a memberof the medical team explained each component of theinformed consent to them in their local language toensure full understanding.On the day of admission and 24 hours later, all patients

were tested for Ebola virus in their bloodstream by quantita-tive PCR. After two negative tests, and if clinically stable,patients were discharged. For anyone testing positive, theywere transferred to the confirmed ward of the ETC andremained hospitalised until they recovered enough to be dis-charged, which was on average ∼16 days. All individuals alsounderwent rapid diagnostic testing for malaria, which wasreported as either positive or negative, although all admittedpatients were empirically treated with a combination anti-malarial agent (Coartem) during their admission to theETC. In addition, all admitted patients received empiricantibiotics, antipyretics and oral or intravenous rehydrationbased on their volume output and degree of dehydration.7

Medical team members in full PPE manually obtainedvital signs at the time of admission and then routinelythree times a day. Blood pressure values were never mea-sured. Temperature was obtained by infrared thermom-eter, pulse by radial artery palpation and respiratory rateby observation.

Personalised physiology analyticsFor data extraction, storage, analysis, visualisation andinitial development of a personalised, predictive,

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automated alerting tool, we used the physIQ (http://www.physiq.com) data analytics platform, known as PPAfor personalised physiology analytics. Their technology isbased on machine learning algorithms that are purelydata driven and can be applied to a wide range of vitalsigns parameters. Using the biosignal waveform datafrom any wearable sensor set, physIQ feature extractionalgorithms generated the following parameters at 1 minintervals: heart rate, heart rate variability (both timedomain and spectral analysis), activity, respiratory rate,pulse transit time (PTT; inversely related to blood pres-sure), posture, ECG quality metric and arrhythmiaburden. Data quality is based on the ECG signal sincemany of the vital signs are derived from the ECG wave-form. An algorithm is applied to the ECG signal thatassesses the ECG information signals strength, motionartefact content and noise levels over 1 min windows ofthe data. This results in a quality metric that rangesfrom 0 to 100% for each min data window. If the metricfalls below 75%, the corresponding 1 min data window isrejected for use in calculating vital signs from the rawbiosignal data.PPA, cleared by the US Food and Drug Administration

in June 2015, is used to detect subtle changes in anindividual’s physiological characteristics from learntbaseline physiological behaviour. This is accomplishedby detecting changes in the inter-relationships betweenparameters, rather than just examining parameters indi-vidually relative to a population norm or statistic. Usingmachine learning technology known as similarity-basedmodelling (SBM) each patient’s current vital signs arecompared with his or her unique baseline in real timeto develop a series of residuals.8 9 These residuals arethen fused into a single index—the Multivariate ChangeIndex (MCI). The MCI represents the likelihood ofchange in the patient’s physiology over time relative tothe learnt baseline, identifying the earliest signs, oftenpresymptomatic, of an improving or worsening medicalcondition that can be graphically presented as a timetrend to healthcare workers. The baseline physiologylearnt by SBM for each patient was based on vital signsdata collected during the first day of monitoring tocapture a full diurnal cycle of physiological activity. As itwas unknown at the time of admission the clinical trajec-tory the patient would follow a version of MCI wasapplied that generates a signed likelihood of changewhere the magnitude is the likelihood of change andthe sign is indicative of improved health conditions(positive) or degraded health conditions (negative).The sign is driven by the patterns produced across themultiparameter SBM residuals at each instant in time. Ifthe monitored vital signs are behaving similarly to thebaseline, the residual values will all be close to zero andthe MCI will be close to zero, indicating no change inphysiology. However, if the monitored vital signs beginto deviate from the baseline, one or more of the resi-duals will increase in magnitude and will be biasedeither positive or negative relative to the amount of

change seen in each vital sign from the baseline period.This pattern of positive, negative and near-zero residualcomponents forms the patterns that drive the sign ofMCI. A detailed explanation of MCI and determinationof baseline deviation can be found in ref. 9

Wearable sensorFor this proof of concept project, we used the MultiSensepatch being developed by Rhythm Diagnostics Systems(http://www.rhythmdiagnosticsystems.com). The MultiSenseis a self-contained, battery-powered, flexible strip, measur-ing 4×1.2 inches and weighing <15 g (see supplementaryfigure S2). It is waterproof with a patented adhesive forreliable adherence to the chest in most situations. It isable to continuously and simultaneously track and storethe following biosignal waveform data: ECG (sampledat 256 Hz), three-dimensional accelerometer (16 Hz),uncalibrated skin temperature (4 Hz), red and infraredphotoplethysmography (PPG; 32 Hz). For this study, themajority of the patches used were first-generation,memory-only devices that stored all physiological data inon-board memory and could be worn for up to 10 dayswith the data then downloaded via Universal Serial Bus(USB) once removed. To demonstrate its efficacy for thecontinuous, real-time streaming of vital signs, the second-generation MultiSense was used for two patients. Thisdevice is otherwise identical to the first-generation devicewith the addition of being Bluetooth-enabled. For thisproject, an Android device running the physIQ app,without cellular connectivity but with Bluetooth andWi-Fi, was used to collect data from the patch and trans-mit it from the contaminated area (red zone) to theclean area (green zone) where personal protective gearwas not required. The Android device was maintained bythe patient’s bedside.

Portable, deployable monitoring infrastructureBasic information technology (IT) infrastructure waslimited in the Makeni ETC, as it would be expected tobe in many settings requiring a rapid medical response.As a result, one of the fundamental requirements of thisproject was to engineer and produce a portable, self-contained ‘system in a trunk’ providing all requiredIT infrastructure except power. The MWPMS neededto be readily shipped and deployable in remote loca-tions without support capabilities. The end result wasa system designed to fit into a Transportation SafetyAdministration-approved container that could bechecked as baggage on a commercial airline (see onlinesupplementary figure S3). The prototype system con-tained a hardened Panasonic Tough Book laptop, pre-loaded and configured to run the physIQ PPA platformfor remote patient monitoring.For this project, two communication systems were pro-

vided. The first was a dedicated private Wi-Fi networkthat provided communication for the wireless patient-worn devices and for the tablets used by the clinicians.A second satellite data link was provided for remote

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system administration that eliminated the need foronsite technical staff. For future projects, the satellitelink would also allow for the patient population to besecurely monitored by clinical staff throughout theworld.The laptop was connected to a hardened self-

contained network hub that provided the entire networkrouting and switching for the system. From the networkhub, the Cat6 Ethernet cable was run up to 300 ft to aweatherproof Wi-Fi radio attached to a high gainantenna. The radio and antenna combination provideda Wi-Fi network that covered the entire Ebola TreatmentUnit (ETU) when centrally located. Power over Ethernetwas used to power the radio from the network hub, elim-inating the need for any additional power cabling to berun to the radio. The satellite link used a Hughes 9502Integrated BGAN radio, which allowed physIQ staff inNaperville, Illinois, USA, to remotely monitor and main-tain the system in Sierra Leone.Since sensor data were received over the Wi-Fi

network, they were stored in a time-series database onthe Tough Book and processed for clinician review bythe physIQ PPA platform. Via the two provided Wi-Fienabled tablets, clinicians could then view, while in thegreen zone, the vitals from the patients as well as thetrending MCI.

Statistical analysisDescriptive statistics were used to describe demographicand clinical characteristics such as coinfections.Pearson’s correlation coefficients were determined forrelationship between continuously sensed and manuallydetermined vital signs. Manually measured vital signsincluded heart rate (peripheral pulse), respiration rate(by observation) and temperature. The time stamps formanually measured vital signs where assigned afterpatient rounds were completed, and could be off fromthe actual time of measurement by 20 min or more. Tocompare to the continuous vital signs measurements,trimmed mean averages of the continuous vital signswere calculated over a time window of ±20 min from thereported manually measured vital signs time stamp. Thetrimmed mean was calculated by taking the average ofthe continuous vital signs data in a 40 min window afterremoving the upper and lower 10% of the samples.Some manually measured vital signs occurred outsidethe period of actual continuous monitoring. Thosesamples were ignored. The remaining manual vital signssamples and continuous vital signs averages were ana-lysed using Pearson’s correlation coefficient over thepatient population. In the case of temperature, since thecontinuous skin temperature measurement is uncali-brated, the difference between the mean of the manu-ally measured temperatures and the continuouslymeasured temperatures for each patient was calculatedand used to offset the uncalibrated readings beforeapplying the Pearson’s correlation coefficient analysis totemperature.

RESULTSAll healthcare providers were trained in the studypurpose, obtaining informed consent, sensor placementand its removal during ∼15 min training sessions foreach of the four medical teams.During the 3-week study period (25 July to 13 August

2015), all eligible patients (n=26) admitted to the ETCwere enrolled in the study. The median age was32.5 years, with the youngest aged 20 and the oldest 70.Thirty-five per cent were female and the average weightwas 54 kg (119 pounds). Presenting symptoms, admis-sion vital signs and diagnoses are presented in table 1.All patients were monitored for the duration of theiradmission except for the two Ebola-positive patients dueto the limited time window for study. Patients withoutEbola were monitored on average for 70 hours, whereasthose with Ebola were monitored for ∼120 hours. Allpatients survived their admission, although the twopatients with Ebola were not discharged until ∼1 weekfollowing the conclusion of the study period.All patients enrolled in the study had the sensor patch

successfully placed and removed by a healthcare workerwhile in full PPE. All 26 patients successfully wore thepatch for the duration of the study without any adversereactions or symptoms of discomfort. For one patient,no data were retrievable due to a presumed batterydrain on the patch prior to placement. For two indivi-duals, the two Ebola-positive patients, their initialpatches fell off within the first 24 hours of wearingthem. The reason for this is unclear and may have beendue to excessive sweating or initial placement issues.They were replaced, with the standard patch adhesivereinforced with a liquid colostomy adhesive, and therewere no further issues with adhesion.A total of 1838 hours of continuous multiparametric

waveform data were collected (a mean of 67.8 hours perpatient), with 91% of the data determined by thephysIQ PPA to be of good quality, with quality deter-mined by passing an ECG signal quality test for usability.Online supplementary figure S4 demonstrates the totalhours of data collected per individual, and the percent-age of good quality data per individual. A screenshotof the streamed waveforms is also shown in onlinesupplementary figure S5.

Comparison to standard vital signsAmong the 25 monitored patients, a total of 112 tem-perature readings, 111 pulse measurements and 111respiratory rate measurements were manually collectedby the Medical team and recorded. The closest continu-ously collected vital sign was compared with eachmanual measurement to assess the level of agreementbetween the two independent measurement approaches(see online supplementary figure S6). The correlationbetween temperature measured by the infrared therm-ometer and the sensor patch was very strong (R=0.99,p<0.001), whereas the correlation for heart rate (R=0.75,

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Table 1 Baseline characteristics of monitored patients

Patient

ID Presenting symptoms/contacts Age Sex

Weight

(kg)

Temperature

on admit (°C)

Pulse on

admit

Ebola

status

Malaria

status

1 Arthralgia/myalgia, anorexia, dizziness, polyuria 54 M x 38.5 72 Negative Negative

2 Diarrhoea, anorexia, abdominal pain. Burial team member 27 M 58 36.6 94 Negative Negative

3 Fever, headache, nausea 20 M 54 36.9 98 Negative Negative

4 Brother of Ebola victim. Mild anorexia and noted to have red

eyes

36 M 60 36.7 84 Positive Negative

5 Fever, headache, nausea, vomiting, diarrhoea, arthralgias/

myalgias and anorexia

20 M 56 36.5 112 Negative Negative

6 Aunt of Ebola victim. Weakness, arthralgias/myalgias,

weakness, red eyes

35 F 54 36.7 x Positive Negative

7 No symptoms. Contact with Ebola victim 33 M 80 36.5 84 Negative Positive

8 Red eyes and headache. Contact with Ebola victim 27 M 73 36.6 87 Negative Negative

9 Fever, headache, red eyes, arthralgias/myalgias, weakness 27 M 53 36.4 93 Negative Positive

10 Fever, nausea, vomiting, anorexia, myalgias/arthralgias 27 M 55 36.0 58 Negative Negative

11 Fever, headache, arthralgias/myalgias 61 M 40 36.5 74 Negative Positive

12 Fever, vomiting, diarrhoea, rash, weakness, arthralgias/

myalgias

30 M 62 36.5 92 Negative Positive

13 Headache, diarrhoea, arthralgias/myalgias, anorexia 60 F 50 36.6 76 Negative Negative

14 Fever, headache, nausea, vomiting, diarrhoea, breathlessness,

anorexia, abdominal pain

22 F 46 36.2 x Negative Positive

15 Nausea, arthralgias/myalgias, weakness, breathlessness,

hiccups. Cold, lightheaded

18 F 39 35.0 Not palpable Negative Positive

16 Fever, chills. Tired. Works at an Ebola treatment facility 33 M 70 36.6 90 Negative Negative

17 Fever, vomiting, arthralgias/myalgias, hiccups, anorexia 55 M 58 36.6 96 Negative Positive

18 Fever, headache, nausea, vomiting, haematemesis, anorexia 60 F x 36.9 84 Negative Positive

19 Fever, headache, vomiting, diarrhoea, anorexia, arthralgias/

myalgias

26 F 44 36.0 70 Negative Negative

20 Dizziness 29 F 46 36.6 98 Negative Positive

21 Arthralgias, anorexia, cough 49 M 54 36.0 76 Negative Negative

22 Abdominal pain, anorexia 35 M 34 35.2 100 Negative Negative

23 Anorexia, headache, fever 32 M 52 36.6 120 Negative Negative

24 Abdominal pain 28 F 61 35.0 82 Negative Positive

25 Fever, nausea, vomiting, diarrhoea at an Ebola checkpoint.

Denies on presentation

35 M 51 36.6 82 Negative Negative

26 Chest pain, vomiting, weakness, breathlessness, anorexia,

abdominal pain

70 F x 35.7 68 Negative Positive

Bold typeface represents positive Ebola and malaria diagnosis.

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p<0.001) and respiratory rate (R=0.83, p<0.001) wereless strong but still robust.

Continuous blood pressure trendsUsing the ECG and infrared PPG signal, PTT wasderived as the inverse of the blood pressure trend. Thisallowed for the continuous tracking of relative bloodpressure and, since the sensor patch also allowed forthe determination of posture and changes in position,changes in blood pressure associated with posturalchanges when transitioning from the lying to the stand-ing position (figure 1).

Multivariate Change IndexIn order to explore the potential for PPA to provide anearly indication for decompensation in an individualpatient, heart rate, heart rate variability, respiratory rateand activity were modelled to develop a MCI for eachindividual that was updated every minute and then aver-aged over 1 hour time windows. An individual’s ‘base-line’ interaction between these measures was learnt overthe first day of monitoring and subsequent improve-ments (+) or degradation (−) in individual vital signsand their relative contribution to the MCI allowed forthe overall physiological status trend of that individual tobe followed. These trends in physiological status are rela-tive to the trained baseline and so even though thepatient is in a degraded health state during training, theMCI indicates improvement or degradation from thatphysiological state, making it possible to determine iftreatment is having a positive or negative effect. Figure 2shows the MCI trends for both Ebola-positive patientsstarting just after the baseline training period. An MCIvalue near zero indicates that the interactions between

vital signs are very similar to the baseline conditions,and so the physiological state is most likely close to thebaseline state. In case (A) of figure 2, the MCI exhibitsthis behaviour for nearly 1.5 days. After that time,the patient’s MCI waxes and wanes but is generally indi-cative of improved vital signs behaviour, given that it islargely positive. The MCI trend for the second patient(figure 2B) behaves quite differently. Here the negativeMCI trend reflects vital signs interactions that are indica-tive of degrading conditions relative to the baselineperiod for the first 2.5 days. During the last day of moni-toring, the MCI trends towards zero, which means thatthe patient’s vital signs interactions are returning tobaseline conditions. In the event of patient decompensa-tion, the MCI would most likely trend persistency muchcloser to a value of −1. This was not seen during themonitoring period, which was consistent with the clinicalfindings.

ECG findingsIn patients with EVD, replacement of fluid and electro-lyte losses is the cornerstone of therapy.10 11 In the ETC,there was no ability to measure electrolyte levels, so weexplored if changes in the ECG over time might provideguidance to electrolyte status.Abnormalities in serum potassium levels are associated

with an increased risk of cardiac arrhythmias, especiallyin the setting of other physiological stresses.12 We wereable to automate the identification of ectopic beats andtrend their frequency over time. Figure 3 shows thetrend of per minute arrhythmia burden along with a30 min moving average in a patient with Ebola over a∼4 days period as they improved clinically with decreas-ing fluid and electrolyte replacement needs.

Figure 1 Representative tracing of the trend in pulse transition time over time showing its variation over a multiday period (A),

and a zoomed in view to show changes with posture (B).

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Changes in the waveform are also common in thesetting of electrolyte abnormalities but have also beendescribed as being associated with viral infections, includ-ing viral haemorrhagic fever.13 14 By comparing ECGwaveforms over time while an individual was in the sameposition, we are able to demonstrate that it is possible toidentify waveform changes (figure 4), although we wereunable to identify a clinical correlate in this setting.

DISCUSSIONThrough this proof of concept study, we have success-fully demonstrated that wireless, multiparametric

monitoring of patients admitted to an ETC in ruralSierra Leone is both feasible and highly desirable byhealthcare workers. While there are obvious short-termclinical benefits to having the capability to continuouslymonitor the vital signs of patients with possibly life-threatening infections, our results support a muchgreater potential benefit to patients, providers andresearchers through the incorporation of real-time dataanalytics. The large number of promising exploratoryfindings for pulse transition time, arrhythmia burden,ECG waveform changes and MCI all support a greatpotential for improving patient care well beyond the

Figure 3 Minute arrhythmia burden of a patient with Ebola over a period of ∼4 days with decreasing fluid and electrolyte

replacement needs. The blue is the per cent of beats that are ectopic each minute. The red line is a 30 min moving average of

the minute burden data.

Figure 2 Representative tracing of the trend in an Ebola-positive patient’s MCI over the monitoring period. MCI, Multivariate

Change Index; PPA, personalised physiology analytics.

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current state of the art by allowing for a more rapidresponse at the earliest signs of decompensation that areunique to that individual – not just for use in the settingof EVD, but rather in any healthcare setting (low-resource or high-resource) where patient decompensa-tion is possible and its earliest recognition is desirable.It has been said that the only good news to come out

of the recent EVD epidemic is that it may serve as awake-up call so that we can be better prepared forfuture similar, if not worse, epidemics that are certain tocome.15 Having the capability to rapidly deploy to any-where in the world a ‘wireless patient monitoring systemin a box’ that enables simplified, continuous monitoringof multiple vital signs, and potentially allows for auto-mated, individualised alerting of decompensation, is oneway to be better prepared. The current study successfullydemonstrated that this type of infrastructure could beprepackaged and deployed into low-resourced areas inresponse to natural disasters or epidemics. Also,although not formally studied, local healthcare workersupport was uniformly enthusiastic. Future work willallow for a formal evaluation of its impact on workflowand satisfaction.Through the limited yet promising work carried out

in this study, we have shown that sensor placement,patient tolerance and the capacity to wirelessly transmitvital signs continuously from a patient care zone to aclean zone are fairly easily achievable. Owing to the rela-tive clinical stability of the patients enrolled, includingthe patients with EVD, we were not able to definitivelydemonstrate the direct clinical benefit of incorporatingsophisticated data analytics into the processing of thesevital sign data, although our results provide compellingevidence of their potential value: relative blood pressurechanges over time and with postural changes wouldinform relative fluid status including early signs of sepsisor blood loss; arrhythmia burden and ECG waveformchanges could be a sensitive indicator of electrolyte dis-turbances or even direct myocardial insult. Most promis-ing would be the continuous tracking of the uniqueinterplay of multiple parameters in a specific individualas expressed by their MCI. The MCI has previously been

studied in remote clinical surveillance of individualswith chronic conditions susceptible to exacerbations andfound to have high sensitivity to changes in physiologicaldynamics and a very low false alert burden.9 The valueof MCI in the current scenario is that it can provide anearly indication of decompensation and also providecaregivers a vigilant, objective measure of physiologicalstatus for all monitored patients in the healthcare facilityrelative to their presenting state. This enables moreeffective and efficient triage in environments withlimited resources and overburdened healthcare workers.Further work in a larger population with greater variabi-lity in clinical course (eg, suspected sepsis population)will help establish the unique value of these derivedparameters for the patient and healthcare worker in theacute management setting.This work was possible only due to the relatively

remarkable progress that has been made over the pastseveral years in the development of miniaturised, wire-less and wearable sensors. These advances in sensorhardware continue to accelerate with a simultaneousdecrease in their cost: over the past decade, the cost ofa microelectromechanical systems sensor has been cutby over half from US$1.30 to US$0.60.16 The MultiSensepatch used in our study is one example of the tremen-dous progress that has been made in wearable sen-sors, and is one of approximately a half-dozen singlepatch, multiparametric sensors currently available. TheMultiSense patch was unique in its incorporation of PPGat the time we designed our programme, althoughanother patch with similar characteristics was recentlyannounced with regulatory approval.17 This representsthe continuously evolving and rapidly changing environ-ment of wearable sensors that expand well beyond justpatches. There are a number of multiparametric sensorsin various stages of development that can be worn onthe wrist, finger, head, skin or as a earbud.5 As with virtu-ally all new technologies, it is likely that over time thecurrent selection and quality of sensors will continue toexpand while the costs drop. As the sensors becomemore and more commoditised, the analytic platform,agnostic to the wireless source of data, will play a central

Figure 4 Change in ECG waveform over time in a patient with Ebola infection.

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role in optimising the value of a comprehensive systemfor improving patient outcomes and healthcare workerefficacy.This proof of concept project successfully demon-

strated that the infrastructure and state-of-the art tech-nology used in the MWPMS could be prepackaged anddeployed into low-resourced areas in response to naturaldisasters or epidemics and used by local resources. Sincethis prototype system was developed using commonlyavailable, off-the-self components and hand built, asdeployed the system cost ∼$15 000. We recognise thatthis is too costly for widespread deployment in low-resource areas. However, in the next phase, it is envi-sioned that this system could be designed and optimisedfor mass production for under $5000 per unit. Since inour experience training required <30 min for a group ofmedical providers, we do not anticipate substantial add-itional costs beyond the hardware needs of the sensorsand servers, but as wireless networks become even moreubiquitous and as sensors further decrease in price, theoverall cost will most likely continue to fall substan-tially.18 Future work with this system will be critical for abetter understanding of costs in various clinical settingsas well as the cost-benefit.

LIMITATIONSThe true benefit of the MWPMS developed can only befully explored in future work using sensors with real-timestreaming of vital signs via a device with regulatoryapproval. This study set-up and equipment did not allowus to explore the usability and clinical benefit of such asystem. Nonetheless, the work described here is a critic-ally important first step in supporting the feasibility oflarger and longer effectiveness studies.

CONCLUSIONIn this small proof of concept study, carried out in anETC in Makeni, Sierra Leone, we were able to demon-strate that continuous vital sign monitoring via a wire-less, wearable sensor supported by the PPA platform canprovide high-acuity monitoring with a continuous,objective measure of physiological status of all patients,and is achievable in virtually any healthcare setting, any-where in the world.

Handling editor Seye Abimbola

Twitter Follow Steven Steinhubl at @SteveSteinhubl

Acknowledgements The authors would like to thank International MedicalCorps for their support, and most especially the many Makeni EbolaTreatment Center healthcare workers and patients. The work described herewas supported by the US Agency for International Development (USAID)through the Grand Ebola Challenge. SRS’ work is also supported by theNational Institutes of Health (NIH)/National Center for Advancing TranslationalSciences grant UL1TR001114 and a grant from the Qualcomm Foundation.

Contributors All coauthors played a role in designing some aspects of thetrial. SRS, DF, CC and ACL collected the data. SWW, GC and SRS carried out

data analytics and drafted the first draft of the manuscript. All authorscritically reviewed and revised the manuscript.

Funding From the USAID’s Fighting Ebola: A Grand Challenge forDevelopment in partnership with the White House Office of Science andTechnology, the Centers for Disease Control and Prevention, and the USDepartment of Defense (award # AID-OAA-F-15-00022).

Competing interests SWW, CC and GC are full-time employees of physIQ.

Ethics approval Ethical oversight and approval was provided by the SierraLeone Ethics Scientific Review Committee.

Provenance and peer review Not commissioned; externally peer reviewed.

Data sharing statement Patient monitoring data will be made available tointerested researchers.

Open Access This is an Open Access article distributed in accordance withthe Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license,which permits others to distribute, remix, adapt, build upon this worknon-commercially, and license their derivative works on different terms,provided the original work is properly cited and the use is non-commercial.See: http://creativecommons.org/licenses/by-nc/4.0/

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