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382 IEEE TRANSACTIONS ON INFORMATION TECHNOLOGY IN BIOMEDICINE, VOL. 9, NO. 3, SEPTEMBER 2005

A Multiparameter Wearable Physiologic MonitoringSystem for Space and Terrestrial Applications

Carsten W. Mundt, Kevin N. Montgomery, Usen E. Udoh, Valerie N. Barker, Guillaume C. Thonier,Arnaud M. Tellier, Robert D. Ricks, Robert B. Darling, Senior Member, IEEE, Yvonne D. Cagle, Nathalie A. Cabrol,

Stephen J. Ruoss, Judith L. Swain, John W. Hines, and Gregory T. A. Kovacs, Member, IEEE

Abstract—A novel, unobtrusive and wearable, multiparameterambulatory physiologic monitoring system for space and ter-restrial applications, termed LifeGuard, is presented. The coreelement is a wearable monitor, the crew physiologic observationdevice (CPOD), that provides the capability to continuouslyrecord two standard electrocardiogram leads, respiration rate viaimpedance plethysmography, heart rate, hemoglobin oxygen sat-uration, ambient or body temperature, three axes of acceleration,and blood pressure. These parameters can be digitally recordedwith high fidelity over a 9-h period with precise time stamps anduser-defined event markers. Data can be continuously streamedto a base station using a built-in Bluetooth RF link or stored in32 MB of on-board flash memory and downloaded to a personalcomputer using a serial port. The device is powered by two AAAbatteries. The design, laboratory, and field testing of the wearablemonitors are described.

Index Terms—Ambulatory physiologic monitoring, Bluetooth,crew physiologic observation device (CPOD), electrocardio-gram (ECG), high altitude, LifeGuard, respiration, vital-signs,wearable.

I. INTRODUCTION

THERE ARE A number of situations in which noninvasiveand continuous monitoring of physiologic and accelera-

tion parameters is extremely useful in an ambulatory or sta-tionary setting. For space applications, these include extrave-hicular activities (EVA, or spacewalks), launch and deorbit, ex-ercise in microgravity, physiologic research, and unanticipatedmedical events [1]. There are also a number of terrestrial settingsin which such capabilities are likely beneficial, including moni-toring of patients with cardiovascular disease to aid in diagnosisand to evaluate therapies, assessing gait stability, activity level,the quality/quantity of sleep, and monitoring of first respondersand accident victims [2]–[5].

Manuscript received October 11, 2004; revised April 13, 2005. This was sup-ported in part by NASA Contracts NCC-1010 and NNA-04CC32A. Humansubject testing was carried out under Stanford University Human Use Protocolnumbers 78 527 (in-lab testing), 79 640 (Licancabur Expedition), and 79 825(KC-135 flight).

C. W. Mundt, K. N. Montgomery, U. E. Udoh, and G. T. A. Kovacsare with Stanford University, Stanford, CA 94304 USA and also with theNASA Ames Research Center, Moffett Field, CA 94035 USA (e-mail:[email protected]; [email protected]).

V. N. Barker, Y. D. Cagle, N. A. Cabrol, and J. W. Hines are with the NASAAmes Research Center, Moffett Field, CA 94035 USA.

G. C. Thonier, A. M. Tellier, R. D. Ricks, S. J. Ruoss, and J. L. Swain arewith Stanford University, Stanford, CA 94304 USA.

R. B. Darling is with the University of Washington, Seattle, WA 98195-2500USA.

Digital Object Identifier 10.1109/TITB.2005.854509

Current technology for ambulatory physiologic monitoringincludes portable patient monitors for bedside and transportmonitoring, and wearable devices for recording electrocardio-graphic data such as Holter monitors [6] and event monitors thatare used for storing electrocardiographic data for subsequentanalysis. Holter monitors record heart rate and/or electrocar-diogram (ECG) continuously for several hours or days, whileevent monitors record these data for brief periods, and onlyupon activation by the user.

Commercially available vital signs monitors include anumber of portable and wearable devices. The Micropaqfrom Welch Allyn (Beaverton, OR), and the ApexPro fromGE Medical Systems (Waukesha, WI) are two of the mostadvanced ambulatory patient monitors available today forwireless portable bedside monitoring and transport monitoring.Both devices measure and wirelessly transmit multiple phys-iologic parameters. The Micropaq acquires heart rate, SpO(an estimate of arterial oxygen saturation SaO measured bypulse oximetry), and several channels of ECG, and transmitsthese to a Welch Allyn FlexNet 802.11 wireless access pointfrom where the data can be distributed for patient monitoring.The ApexPro has similar capabilities, but can also be interfacedto an external blood pressure device (Accutracker DX, SuntechMedical, Morrisville, NC). Both devices rely on access to awireless infrastructure and do not record data internally. Thislimits their use to well-equipped, relatively benign environ-ments, such as hospitals. Commercial Holter monitors, eventrecorders, and transtelephonic monitors do record data, butonly heart rate and one or more channels of ECG. They do notstream these parameters wirelessly in real-time.

Other commercial devices for monitoring vital signs includePCMCIA-Cards for measuring ECG, SpO , blood pressure,and carrying out spirometry (QRS Diagnostics, Plymouth,MN), sleep study devices [Nellcor Puritan Bennett (Melville)Ltd., Kanata, ON, and Itamar Medical Inc., Boston, MA]and shirt-type devices with attached or integrated physiologicsensors (Vivometrics, Ventura, CA, and Sensatex, New York).A flexible vital signs monitoring system for sports and mil-itary applications was developed by FitSense Technologies(Southborough, MA), but it does not support the recording andtransmission of electrocardiograms. However, FitSense doesprovide a good solution for low-bandwidth vital signs transmis-sion with their proprietary BodyLAN system and an evaluationof their system during a Mount Everest expedition has beenreported in [7] which also provides an excellent description ofthe evolution of wearable health data monitoring.

1089-7771/$20.00 © 2005 IEEE

MUNDT et al.: MULTIPARAMETER, WEARABLE PHYSIOLOGIC MONITORING SYSTEM 383

A number of efforts to develop wearable monitors have beenreported [8]–[21]. These include transtelephonic ECG moni-tors [8], personal computer memory card industry association(PCMCIA), and Compact Flashcard-based Holters [9], [10],Holters transmitting ECG wirelessly through a global systemfor mobile communications GSM() modem [11], [12], wearableECG monitors with real-time user feedback [13], and monitorsthat transmit real-time ECG data over the Internet [10]. Rhee etal. developed a wearable photoplethymographic “ring-sensor”and integrated it with an ad-hoc self-organizing wireless net-work [14], and Paradiso is developing wireless, instrumented,smart-fiber garments [15]. Most of these systems demonstratenew technologies and methods that advance the state of theart, but are generally prototypes that lack the integration androbustness to meet space flight requirements.

Despite recent advances in medical technology, none of thecurrently available devices provides a combination of weara-bility, size, and functionality that satisfies demanding NASA re-quirements or allows the devices to be used in clinical studieswhere body motion and physiologic parameters are to be in-vestigated simultaneously. The goal of this effort was to designa small, lightweight, wearable, ergonomic device that not onlyrecords and streams a comprehensive set of diagnostic-qualityphysiologic parameters, but can also record body position andorientation, acceleration in three axes, and can be used to markevents. This feature set, combined with wearability, alarm indi-cators, fault detections, and the ability to stream data to hand-held Bluetooth-enabled devices, forms a compact and reliablesystem that not only improves medical care in space flight, butalso enables a new range of physiologic studies to be performedin terrestrial applications, including medical care.

II. METHODS AND MATERIALS

The LifeGuard system consists of the CPOD device and aportable base station computer. The CPOD device, the corecomponent of the system, is a small, lightweight, easy-to-usedevice that is worn on the body along with the physiologicsensors described below. It is capable of logging physiologicdata as well as wirelessly transmitting data to a portable basestation computer for display purposes and further processing[Fig. 1(a)].

A. Physiologic Sensors

A matrix listing typical physiologic parameters for a numberof application scenarios, including commercial and military sce-narios, was generated since it was anticipated that such a systemmight prove very useful in terrestrial medical applications aswell. This matrix was then used to choose a final set of phys-iologic parameters representing a common denominator for allinvestigated applications.

Most physiologic parameters supported by LifeGuard aremeasured with sensors that are external to the CPOD wearabledevice and can be configured as needed. The only sensorsthat are integrated into the CPOD are the accelerometers.Temperature can be measured in one of two ways: either withan ambient temperature “plug,” or with a probe (cable) for skin

or core temperature measurements. ECG and respiration sig-nals are acquired using commercial button electrodes that areconnected to the CPOD via snap-leads (such as Red Dot types2249 and 2237 from 3M, St. Paul, MN). Pulse oximetry (SpO )is measured with a Nonin pulse oximeter (Nonin Medical Inc.,Plymouth, MN), which is typically attached to a finger (fingerclip or flexible wrap) or ear lobe (ear clip). For applicationsrequiring subject mobility, the flex finger sensor from Nonin(model 8000J) was optimum. Nonin pulse oximeters are usedwith a mating signal conditioning and digitization unit—theXpod. The Xpod used for LifeGuard (model 3011) streamsserial data to the CPOD at a rate of about one sample persecond.

A cuff-based device is used to measure systolic and dias-tolic blood pressures. For applications involving significant mo-tion or vibration, an auscultatory motion-tolerant device can beused. The LifeGuard system supports the Accutracker II (Sun-tech Medical, Morrisville, NC), one of the most motion-tolerantdevices available.

Depending on the application, either all of the external sen-sors or any desired subset can be used. In many cases, ECG,respiration rate, activity (acceleration), skin temperature, andheart rate (derived from ECG through post-analysis) will suf-fice. This configuration only requires the ECG/respiration elec-trode set and provides the greatest degree of mobility.

Fig. 1 (b) illustrates how the CPOD device is worn on thebody. Amphipod sport packs (Amphipod, Inc., Seattle, WA) areused to secure the device around the waist.

B. Prior Research Prototype System

Initial development efforts by our group were focused onusing commercial portable digital assistant (PDA) technologyas the platform for physiologic data acquisition under theMicrosoft Windows CE operating system. A prototype systemusing commercial off-the-shelf components was first devel-oped to refine requirements and to gain understanding aboutthe real-world use of such a device. This “Smart HealthcareManagement System” (SHMS) consisted of an easy-to-applyphysiologic sensor pad (Nexan Ltd., Cambridge, UK), whichprovided a two-lead ECG and respiration signals. The elec-tronics of the Nexan sensor was modified so that it transmittedits digitized data wirelessly using Bluetooth technology to apersonal digital assistant (PDA, a Compaq/HP iPaq Pocket PC)running Windows CE (Microsoft, Redmond, WA). This PDAwas worn on the body and could record data locally and/ortransmit data in real-time via 802.11b (IEEE wireless localarea network standard) over the Internet to a central server (aswitchboard) where multiple devices (PCs, PDAs) could viewthe data live via the Internet.

The SHMS system was used for in-lab and field testing (in-cluding a high-altitude research study), and provided valuablereal-world experience. A number of shortcomings were identi-fied, including the lack of robustness of connectors, short bat-tery lifetime, and external dependencies on commercial off-the-shelf components (iPaqs, WindowsCE) that were not designedto meet the high reliability requirements of medical monitors.As a research prototype system the SHMS provided a mecha-nism for successfully demonstrating functionality and refining


Panel A

Panel B

Fig. 1. Panel A: LifeGuard System. 1) (a) CPOD vital signs monitor with physiologic sensors, including (b) electrodes for recording ECG and respirationwaveforms, (c) pulse oximeter measuring SpO and heart rate, and (d) blood pressure monitor. 2) Diagram illustrating locations of CPOD monitor and sensors onbody. 3) Communication options (RS-232 hardwired or Bluetooth wireless) for data transfer between CPOD and (e) base station computer. Panel B: Photograph ofsubject with cutaneous disposable electrodes in place on upper chest and left side, as well as a fingertip pulse-oximeter sensor. An Amphipod sport pack (Amphipod,Inc., Seattle, WA) is used to secure the device around the waist.

requirements for an eventual system, but was not capable ofmeeting the goal of a rugged physiologic monitoring system thatwas reliable and easy to use. A new, refined and optimized so-lution was required, and to be derived from careful examinationof requirements across a broad range of applications. This ef-fort resulted in the development of the LifeGuard system andthe CPOD device.

C. Technical Specifications of CPOD Device

Table I lists the technical specifications of the CPOD. Manyof these, such as battery lifetime, data storage capacity, andwireless range, are the result of trade-offs between the final sizeand form factor of the device, its usability, and its feature setand functionality. For example, AAA batteries represented thebest trade-off between battery size and capacity for this partic-ular device. Primary cells were chosen over rechargeable batterypacks due to their availability and ease of replacement.

A custom LCD panel displays information on the devicestatus (logging, streaming, connection to base station) as wellas cycles through the measured parameters (skin temperature,activity, heart rate, SpO , systolic and diastolic blood pressure,and remaining battery life). A button on the front of the devicecan be used to create and store event markers (the CPODalso incorporates an internal real time clock), and to enablethe Bluetooth module. It can also stop the cycling display tocontinually show a single parameter. A piezo buzzer is usedto alert the user of low battery life, low SpO , or high heartrate values. It also serves to signal an alarm when a sensor isdisconnected or not functioning properly.

The CPOD acquires and logs physiologic data and can down-load or stream this data on demand in real time to a base stationdevice such as an IBM-compatible PC or Pocket PC. It also pre-processes the acquired signals, which currently includes scalingand averaging. The central element of the CPOD is a low-power


TABLE ICPOD TECHNICAL SPECIFICATIONS

Fig. 2. Detailed photographs of CPOD device and illustration of its functional elements.

microcontroller that controls all peripheral devices, including anA/D converter, and 32 MB of on-board flash memory. The sam-pling rate for each parameter is programmable. At the defaultsampling rates (ECG at 256 S/sec, respiration at 64 S/sec, accel-eration at 16 S/sec, temperature, SpO and heart rate at 1 S/sec)the CPOD can log data for up to 9 hours. The device has fourports for external sensors and one RS-232 port for hardwiredtransfer of logged physiologic data to a PC.

The CPOD device is shown in Fig. 2, and a block diagramof the electronics of the device is shown in Fig. 3. One designchallenge was to maintain a constant sampling rate across allchannels while at the same time storing data in flash memory.This was accomplished by using flash memory chips with twobuilt-in SRAM buffers (AT45DB642, Atmel, San Jose, CA).This allows continuous transfer of data to one of the two buffersof the memory chip, and periodic programming of the buffercontents to the nonvolatile flash memory.

The CPOD can stream data wirelessly via Bluetooth. Blue-tooth was chosen as wireless technology due to its commer-cial availability and increasing industry support. Many lap-tops, Tablet PCs, PDAs, and cellular phones have Bluetoothbuilt-in, thereby greatly simplifying the hardware of the basestation or client device that is used to display the data fromthe CPOD.

The CPOD was designed with a major consideration beingease of use. Device setup and data download are accomplishedentirely from the base station computer. Once programmed, thedevice can be turned off until the time of use. Once turned on,the device will log the data from all physiologic sensors it wasprogrammed to use. The only interaction the user has with thedevice is through the event button and status display. The usercannot change the basic operational mode of the device (loggingor streaming), ensuring that the system meets the high reliabilitystandards of medical monitoring devices.


Fig. 3. Block diagram illustrating the main elements of the CPOD electronics.

TABLE IICPOD TESTING SUMMARY. THESE TESTS WERE PERFORMED ON THE CPOD ONLY, NOT ON PERIPHERAL SENSORS

III. RESULTS

A. Laboratory and Field Testing

Laboratory testing focused on verification and validation ofthe data that the device records, as well as environmental andoperational testing to ensure that the device is operational inextreme environments (see Table II). Verification and valida-tion tests used data from signal generators and ECG simulatordevices to verify that the device provided the correct output.Further tests comparing the output of the device with that of acommercial vital signs monitor (Propaq 106 EL, Welch Allyn,Beaverton, OR) were also performed. The analog front-end de-sign was optimized to provide the highest signal fidelity pos-sible. These changes were verified in laboratory and field tests;details are described in the following paragraphs.

A series of field tests was undertaken to validate and refinethe design of the device. To expose the system to a variety ofenvironmental and physiologic conditions, tests were carried

out in medium- to high-altitude alpine environments. For eachtrial, subjects were instrumented and then engaged in high-ex-ertion activities. The test series involved snowshoeing throughDonner Pass and climbs on Mt. Adams, Mt. St. Helens, andMt. Shasta. In each case, hardware and software issues were de-tected and then corrected. One change involved increasing theinput impedance of the ECG input amplifiers from 10 M to 100M to improve common mode rejection. This modification, incombination with an increase in the high-pass cut-off frequencyfrom 0.05 to 0.5 Hz, helped to reject motion artifacts and sta-bilize the ECG baseline. This greatly facilitated the real-timemonitoring of ECG signals of moving subjects. To verify thatthis reduction in ECG bandwidth was acceptable for our pur-poses, a series of simulator-generated ECG arrhythmia wave-forms was acquired and transmitted by the CPOD and then an-alyzed and correctly identified by cardiologists. Another designchange targeted battery life. The main dc-dc converter of thedevice was redesigned to allow a more complete utilization of


Fig. 4. CPOD Hardware Revisions. (a) Beta version of the device. (b) Finalversion.

Fig. 5. Physiologic data recorded during high-altitude trial. SpO is indicatedby the black line and heart rate data by the gray line. The recording coversapproximately 4.5 h during an ascent of the Licancabur volcano. Time recordedand displayed is in Pacific Standard Time.

the capacity of the AAA batteries by choosing a more efficientstep-up converter that can accept input voltages down to 0.7 V.The power management of the Bluetooth module was optimizedas well by implementing a sleep mode that turns the module offif not used for a period of 60 s. One significant issue was theidentification of suitable disposable electrodes for the ECG andrespiration sensors. After much testing, the electrodes with thebest adhesion properties were determined to be 3M Red Dottypes 2249 and 2237 (3M, St. Paul, MN). Many of these testsexposed the CPOD device to very low temperatures C aswell as numerous shock conditions, and proved the superiorityof flash memory for data storage over conventional hard-drives.

Valuable user feedback resulted from these initial trials thatled to an ergonomic redesign of the casing for the final design(Fig. 4). This feedback focused on the robustness of connectorsand comfort, and led to the use of LEMO (LEMO, Ecublens,Switzerland) connectors for all sensors to prevent accidental un-plugging of leads, and the tapering of the sides of the devicefor improved comfort. Using a custom-designed Delrin casingin combination with a stacked board configuration helped sig-nificantly to keep the size of the CPOD small without sacri-ficing robustness. These initial tests used the device in a datalogging rather than wireless transmission mode of operation,and because of the requirement for subsequent downloading and

Fig. 6. Subject preparing for a dive at the Licancabur summit. The white cablevisible at the lower edge of the photograph (arrow) connects to the remoteoxygen saturation sensor.

Fig. 7. Physiologic data recorded during two dives in the summit lake[elevation 5900 m (19 400 ft) MSL]. SpO is indicated by the black line andheart rate data by the gray line. The dives started at 5:36 am and 5:44 am,respectively, and lasted about 2 min. The data illustrates a classic dive reflexcharacterized by a lowering of heart rate with gradual decrease in SpO untilsurfacing and breathing.

browsing of data, a number of improvements in user interfacedesign and functionality in the base station software were in-corporated. As was found with the earlier PDA-based SHMSsystem, early use of the device in real-world scenarios promptediterative refinements in design and thus shortened the develop-ment process.

B. Mission Oriented Testing in Extreme Environments

1) Space Station Analog: The first evaluation of the systemin a NASA test environment occurred in March of 2003 in theNASA Extreme Environment Mission Operations (NEEMO) fa-cility, an underwater analog to the space station environment ata depth of 18 m (60 ft) located off Key Largo, FL. The maingoal of this test was to evaluate ease of use and wearability.A further goal was to evaluate the feasibility and reliability ofradio-frequency transmission within the metal-walled facility.


Fig. 8. Data streaming setup at the Licancabur summit camp (left) and real-time data display at Stanford University (right). Physiologic data acquired by theCPOD was sent to a base station computer (tablet PC), and then transmitted by a satellite terminal to an INMARSAT communications satellite and from there toStanford University.

In this field test, astronauts used the device to monitor physio-logic parameters during exercise and to monitor a crewmemberduring a simulated medical emergency. Positive feedback wasreceived on wearability and usability of the system, and the fea-sibility of using Bluetooth in such an environment was demon-strated.

2) High Altitude: The first significant mission-orientedtesting of the system occurred in October and November of2003. During a connected pair of expeditions, a number of sub-jects were monitored when awake and asleep over an altituderange from sea level to approximately 6100 m (20 000 ft) meansea level (MSL). The first expedition took place in the AtacamaDesert of Chile, and involved geologic and biological surveys ofa Mars-like region. The second expedition started at the base ofthe Licancabur volcano on the Chile/Bolivia border, involved asurvey of high-altitude lakes at approximately 4,300 m (14 000ft) MSL. This was followed by a climb to approximately 6100m (20 000 ft) MSL and then free-dives in a lake at that altitude.During these expeditions the CPOD instrument operated inthree modes: freely moving subject/internal data recording,cabled but mobile underwater subject/internal data recording,and stationary subject with real-time satellite data streaming.

Freely moving subjects were wired using the full cutaneouselectrode set and oximeter sensor as shown in Fig. 1. This setupallows unobtrusive physiologic monitoring during exercise,hiking, and climbing. Several subjects were monitored duringthe ascent of the Licancabur volcano, and their ECG, respira-tion, SpO , heart rate, and activity were recorded. An exampleof the data is shown in Fig. 5.

At two locations [Lake Helen, CA, N 40 deg. 29 49 , W121 deg. 11 7 , altitude 2400 m (8000 ft) MSL] and the Li-cancabur summit lake [S 22 deg. 50 03 , W 67 deg. 53 00 ,altitude 5900 m (19 400 ft) MSL], SpO and heart-rate datawere acquired during shallow [ 3 m (10 ft)] dives in fresh

water, using custom-made 15-m (49-ft) cabled fingertip pulseoximeter units (Fig. 6). Data recorded during one of these divesis shown in Fig. 7. This data shows a classic dive reflex loweringof heart rate, with gradual decrease in SpO until surfacing andbreathing.

To demonstrate real-time satellite data streaming, theCPOD was connected to the serial port of a Getac tablet PC(CA25, Getac, Inc., Lake Forest, CA). The custom LifeGuardBaseStation software was set up to stream data through aUSB-connected ISDN modem (USB ISDN TA, Draytek,Hsin-Chu, Taiwan). The modem was connected to a Thrane &Thrane Capsat Messenger satellite terminal (Thrane & Thrane,Lyngby, Denmark), with data traffic directed to and from theEOR-W Inmarsat communications satellite from the Lican-cabur crater rim summit camp location [5900 m (19 400 ft)MSL]. The satellite transceiver was erected within an alpinetent at the summit camp. The net data throughput achieved was64 kbits/sec, although the LifeGuard system can stream dataover a much smaller bandwidth (9600 b/s) using its customprotocol. These data were transmitted through the satellite todownlink stations at France Telecom, then across the Internet inreal-time to the switchboard server located at Stanford Univer-sity, Stanford, CA. From there, clinicians and other observerswere able to connect in to view the data stream live as it wasreceived. Fig. 8 shows both the transmitting and receiving endsof the operation.

IV. DISCUSSION

LifeGuard was developed to provide a wireless vital signsmonitor incorporating the ability to measure and record a com-prehensive set of physiologic parameters, and housed withina small, compact, lightweight case that offers excellent wear-ability and ergonomics. This allows the device to be used forcontinuous unobtrusive monitoring during operations in remote


and/or extreme environments where real time physiologic datawould be useful such as in astronauts experiencing an emer-gency onboard the space station or shuttle, wounded soldiers onthe battlefield, or fire fighters and first responders during searchand rescue missions. Another unique aspect of the CPOD de-vice is its capability of recording acceleration and body posi-tion information along with physiologic parameters. This fea-ture enables activity and gait assessment, and if configured withonly the pulse oximeter sensor even monitoring of high perfor-mance athletes. Furthermore, the ability of the CPOD to simul-taneously log and stream data allows this device to be used forrecording physiologic data during expeditions in remote areasand extreme environments, while at the same time providingthe means to wirelessly check the health status of expeditionmembers in real-time. Finally, the ability to configure the sen-sors connected to the CPOD as needed allows size, weight, andsetup time of the system to be minimized.

V. CONCLUSION

In summary, a versatile, multiparameter wearable physio-logic monitor capable of 9-h on-board digital data storage aswell as real-time wireless data streaming has been developed.The system has broad applicability in space and terrestrialsettings, including emergency and nonemergency medicalmonitoring of subjects in extreme environments. The systemhas been demonstrated to operate successfully in three differentmodes: freely moving subject; cabled subjects (for underwaterstudies); and remote subjects with real-time satellite telemetry.To date, more than 30 subjects have worn the LifeGuardsystem in various modes and environments, some of them forstudies lasting several days. The general feedback has beenvery positive. The system is currently being evaluated in testdeployments for space-related research (centrifuge experi-ments) within NASA. In addition, the system will be evaluatedin clinical environments to obtain valuable input for furtherimprovements of the CPOD device itself and the accompanyingdata analysis software package.

ACKNOWLEDGMENT

The authors would like to thank the National Geographic So-ciety for their support of the Licancabur 2003 Expedition.Theywould also like to thank the Licancabur 2003 Expedition Sci-ence Team: E. A. Grin, A. Hock, A. Kiss, G. Borics, K. Kiss, E.Acs, G. Chong, C. Demergasso, R. Sivila, E. Ortega Casamayor,J. Zambrana, M. Liberman, M. Sunagua Coro, L. Escudero, C.Tambley, V. Gaete, R. L. Morris, B. Grigsby, R. Fitzpatrick, G.Hovde, their local guides, and the team of wonderful porterswithout whom this expedition would not have been possible.

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Carsten W. Mundt received the M.S. degree in elec-trical engineering from the Technical University ofDresden, Dresden, Germany, in 1994, and the Ph.D.degree in electrical engineering from North CarolinaState University, Raleigh, in 1997.

His experience includes embedded and wire-less systems design, firmware development, dataacquisition design, biotelemetry, and biomedicalsensor development. He has been with NASAAmes, Moffett Field, CA, since 1997 and joinedStanford University, Stanford, CA, in 2001, where

he continues to support NASA projects within the National Center for SpaceBiological Technologies. His current work is focused on wearable, wireless,physiologic monitors, and free-flyer satellites for biological research in spaceand medicine.


Kevin N. Montgomery received the Ph.D. degree incomputer engineering from the University of Cali-fornia, Los Angeles.

He is currently the Engineering Director of theNational Center for Space Biological Technolo-gies (NCSBT) at Stanford University, Stanford,CA. Earlier, as Technical Director of the Na-tional Biocomputation Center, his team developedtechnologies in computation, visualization, andsimulation in medicine and surgery. Researchprojects included computer-based surgical planning,

intraoperative assistance systems, surgical simulators, anatomical atlases, andwireless telemedicine/telemetry. He regularly serves on several study/reviewsections for DoD, NIH, NSF, and other granting agencies, as well as advisesand consults with several small, high-tech companies in the Silicon Valley.

Usen E. Udoh received the M.S. degree in electricalengineering from North Carolina State University,Raleigh, in 1999. His emphasis was in embeddedsystems and ASIC design.

He has over six years of experience in industryin development of wearable systems and wirelessplatforms. He has previously represented the wire-less community and has several patents relatedto Bluetooth technology. He joined NASA AmesResearch Center, Moffett Field, CA, in 2001, wherehe was involved in the development of wearable

devices for applications in space and medicine. He continues to support NASAprojects on wearable monitors and autonomous biological analytical systemsat the National Center for Space Biological Technologies (NCSBT), StanfordUniversity, Stanford, CA.

Valerie N. Barker received the B.S. degree in me-chanical engineering from San Jose State University,San Jose, CA, and the M.S. degree in electromechan-ical engineering from Stanford University, Stanford,CA.

She is currently a Mechanical Engineer at NASAAmes Research Center, Moffett Field, CA. She hasapplied her multidisciplinary skills on a variety ofprojects including wearable physiologic monitorsand biosensors for the detection of chemical andbiological warfare agents. Currently, she is the Lead

Thermal Engineer for an autonomous genomics payload scheduled to launch atthe end of 2005.

Guillaume C. Thonier received the M.S. degree inelectrical engineering from the Ecole Polytechnique,Paris, France, and the M.S. degree in computer sci-ence from Stanford University, Stanford, CA.

He has eight years of technical experience in com-puter graphics, virtual reality, artificial intelligence,network programming, and software development.He is currently a Senior Research and DevelopmentEngineer for the National Biocomputation Center/National Center for Space Biological Technologies(NCSBT), Stanford University. Current research

includes the development of a software interface for a Smart HealthCare Mon-itoring System, designed to process, store and display real-time physiologicaldata on a PC-based or embedded platform.

Arnaud M. Tellier received the M.S. degree in engi-neering from Ecole Centrale Paris, France, the M.S.degree in oceanography from Florida Atlantic Uni-versity, Boca Raton, and the M.S. degree in computerscience from Stanford University, Stanford, CA.

He has eight years of technical experience inimage processing, computer graphics, virtual reality,network programming, and software development.He is currently a senior research and developmentengineer for the National Biocomputation Center, ajoint NASA-Stanford institute for applying advanced

computational and visualization technologies for medicine and surgery.

Robert D. Ricks received the B.S. degree in elec-trical engineering from Purdue University, WestLafayette, IN, in 1958.

He is currently a Senior Analog Design Engineerand Chief Engineer of the NASA Ames AstrobionicsProgram, Stanford University. Stanford, CA. He has47 years of experience in diverse projects in med-ical, consumer, and NASA related programs. He hasa 41–year association with NASA, 25 years as a con-sultant, and the last 16 years as a full-time employee.He holds four U.S. patents, and one pending.

Robert B. Darling (S’78–M’86–SM’94) was bornin Johnson City, TN, on March 15, 1958. He receivedthe B.S.E.E. (with highest honors), M.S.E.E., andPh.D. degrees in electrical engineering from theGeorgia Institute of Technology, Atlanta, in 1980,1982, and 1985, respectively.

He has been with the Department of Electrical En-gineering, University of Washington, Seattle, since1985, where he is presently a Professor of electricalengineering, an Adjunct Professor of bioengineering,and Director of the Electrical Engineering Microfab-

rication Laboratory. His research interests include electron device physics, de-vice modeling, microfabrication, circuit design, optoelectronics, sensors, elec-trochemistry, and instrumentation electronics.

Yvonne D. Cagle received the B.S. degree in bio-chemistry from San Francisco State University, SanFrancisco, CA, in 1981, and the M.D. degree fromthe University of Washington, Seattle, in 1985.

She is a NASA Astronaut currently assigned as theAstronaut Liaison to NASA Ames Research Center,Moffett Field, CA, and serves as the Astronaut Med-ical Advisor to the National Center for Space Bio-logical Technologies. She is a Consulting Professorat the Department of Electrical Engineering, StanfordUniversity, Stanford, CA. She is a USAF Colonel cer-

tified as a flight surgeon, board-certified in family practice, and certified as aFAA Senior Aviation Medical Examiner and ACLS Instructor. She is a ClinicalAssistant Professor at The University of Texas Medical Branch (UTMB), Galve-ston, and The University of California at Davis. Her research interests includeaerospace physiology, space adaptation syndrome, autonomic dysfunction, neu-roplasticity, epilepsy, and brain injury.


Nathalie A. Cabrol is a Planetary Geologist atNASA ARC/SETI Institute, Moffett Field, CA,specialized in the evolution of water on Mars.

She is a Co-I of the Mars Exploration Rovermission and PI of a NAI-funded project exploringthe highest lakes on Earth as analogs to ancientMartian lakes. She develops exploration strategiesfor the robotic search of life in the Atacama Desertas a simulation for future astrobiological missionsto Mars. She has over 250 publications and profes-sional communications. She authored three books

and several chapters of books.In 2005, Dr. Cabrol was elected Carey Fellow and Women of Discovery (Air

and Space).

Stephen J. Ruoss is an Associate Professor ofMedicine in the Division of Pulmonary and CriticalCare Medicine, Stanford University, Stanford, CA,where he serves as Co-Chief.

His research interests include high altitude phys-iology and human adaptation, as well as other lunginjury and chronic pulmonary infection investi-gation. He has extensive experience at altitude, aconsequence of his paired interests in high altitudephysiology as well as climbing.

Judith L. Swain is Professor of Medicine, Dean forTranslational Medicine, and the Founding Directorof the College of Integrated Life Sciences (COILS),University of California, San Diego.

She is widely known in the field of molecularcardiology, and pioneered the use of transgenicanimals to understand the genetic basis of cardiovas-cular development and disease. Her current researchinterests are centered on the assessing and enhancinghuman performance. She is currently Co-Directorof the NASA National Center for Space Biological

Technologies, Stanford University, Stanford, CA.

John W. Hines received the B.S. degree in electricalengineering from Tuskegee University, Tuskgee, AL,and the M.S. degree in biomedical and electrical en-gineering from Stanford University, Stanford, CA.

He is currently a Senior Research Scientistat NASA-Ames Research Center, Moffett Feild,CA, and Manager of the Astrobionics IntegratedProgram/Project Team which develops advancedbiomolecular and biomedical technologies forNASA’s Human Exploration and Biological Re-search Missions and Programs. He has nearly 30

years of combined NASA and Air Force experience in biological and biomed-ical technology development, project management, engineering, and LifeSciences Spaceflight hardware development.

Gregory T. A. Kovacs (M’83) received the BA.Sc.degree in electrical engineering from the Universityof British Columbia, Victoria, BC, Canada, in 1984,the M.S. degree in bioengineering from the Univer-sity of California at Berkeley, in 1985, and the Ph.D.degree in electrical engineering and the MD degreefrom Stanford University, Stanford, CA, in 1992, re-spectively.

He possesses extensive industry experienceincluding co-founding several companies, most re-cently, Cepheid, Sunnyvale, CA. He is an Associate

Professor of electrical engineering with Stanford University with a courtesyappointment in the Department of Medicine. In addition, he is the Director ofMedical Device Technologies for the Astrobionics Program of the NASA AmesResearch Center, and for the Stanford–NASA National Biocomputation Center.He helps direct a variety of projects spanning wearable physiologic monitors,biosensor instruments for detection of chemical and biological warfare agentsand space biology applications, and free-flyer experiment payloads. He servedas the Investigation Scientist for the debris team of the Columbia AccidentInvestigation Board, having worked for the first four months after the accidentat the Kennedy Space Center, FL. In this role, he carried out physical, photo-graphic, X-ray, chemical, and other analyses on selected items from the nearly90 000 lb of recovered debris and worked toward understanding the nature ofthe accident. His current research interests include biomedical instruments andsensors, miniaturized spaceflight hardware, and biotechnology.

Dr. Kovacs is a long-standing member of the Defense Sciences ResearchCouncil (DARPA) and has served as an associate chair and chairman. He isa Fellow of the American Institute for Medical and Biological Engineering. Heheld the Noyce Family Chair and was a Terman and then University Fellowat Stanford University. He was the recipient of a National Science Foundation(NSF) Young Investigator Award.