Abstracts

Symposium on Physiological Monitoring

February 21, 2008

Abstracts

Plenary Speakers

“Diabetes Mellitus - Why Monitor Glycemia?”

Catherine Carver, MS,APRN,BC,CDE

Interim, VP Clinical Services

Joslin Clinic

Diabetes is a group of related conditions each resulting in elevated blood glucose levels. Insulin, a hormone secreted by beta cells in the pancreatic islets is mainly responsible for controlling blood glucose levels. The inability to produce insulin or the inability to use insulin effectively results in hyperglycemia. Chronic hyperglycemia is associated with several diabetes complications including retinopathy, nephropathy, neuropathy and cardio-vascular disease. These complications appear to be directly related to elevated blood glucose.

Because diabetes is a largely self-managed illness the self monitoring of blood glucose is important. Many factors affect the ability of patients to achieve and maintain near-normal blood glucose levels. Things that must be considered are age, co-morbidities, physical limitations, support system and the patient's ability to recognize and treat hypoglycemia. Presently self-monitoring of blood glucose via episodic finger stick method is what we have available as well as continuous glucose sensing via a sub-cutaneous sensor and this method requires finger stick blood glucose readings to calibrate.

Objectives:

After this presentation you will be able to:

1. Identify the various types of diabetes 2. Describe the relationship of blood glucose levels and complications 3. Describe the challenge of the person with diabetes to monitor their blood glucose with present technology

"Continuous Glucose Monitoring: Challenges and Benefits"

Howard Wolpert, MD

Senior Physician and Director of the Diabetes Technology Translation Program,

Joslin Diabetes Center

The widespread adoption of continuous glucose monitoring promises to be an important advance in diabetes care. The benefits of intensive glucose control in preventing the long-term complications of diabetes are couterbalanced by a marked increase in hypoglycemia that adds to the morbidity and mortality associated with diabetes. Intermittent fingerstick glucose measurements give the patient with diabetes only a 'snap-shot' picture of their glucose fluctuations, and this limitation makes it extremely difficult for individuals striving to keep their glucose levels in a tight target range to avoid hypoglycemia. Continuous glucose monitoring provides real-time glucose measurements, trend/direction of change information and alarms of impending hypo- and hyper-glycemia. Initial short-term trials show that use of this new technology allows patients to intensify glucose control with less associated risk for hypoglycemia. Current devices measure interstitial fluid, rather than blood, glucose levels, and because of physiologic lag the glucose concentration in these fluid compartments will sometimes be different. This lag has important implications for sensor calibration, alarm accuracy, and the use continuous monitoring in real-time diabetes management.

 “Assessing skin function using spectroscopy”

Apostolos Doukas, Ph.D.

Wellman Laboratories of Photomedicine, Associate Physicist, Massachusetts General Hospital and Assistant Professor, Department of Dermatology, Harvard Medical School

Optical technologies expand the spectral range of observation and quantify visual assessment. The aim of optical diagnostics is to identify molecular species by their absorption, emission or scattering properties that correlate with physiological conditions. Fluorescence excitation spectroscopy has been applied to skin in vivo to assess skin function, specifically to measure epidermal proliferation, differentiate irritant from allergic contact dermatitis and follow the wound healing process.

“In vivo Sensor Technology for the FreeStyle NavigatorTM

Continuous Glucose Monitoring System”

Tianmei Ouyang, Ph.D.

Associate Research Fellow

Abbott Diabetes Care

FreeStyle Navigator is a continuous blood glucose measuring system which is designed to provide real-time glucose values updated each minute for up to five days, as well as glycemic alarms and glycemic trend information.

Navigator is based on a transcutaneous glucose sensor, which is self-inserted, and self-calibrated by the user.  The sensing element is based on a Wired EnzymeTM sensing element, which operates at a very low potential of 40 mV vs. the Ag/AgCl reference electrode.  In contrast, conventional hydrogen peroxide-based transcutaneous glucose sensors (such as the Medtronic-Minimed CGMS) operate at approximately 500 mV vs. the Ag/AgCl reference.  There are two primary advantages of this system:

  1. Navigator is much less sensitive to electrochemical interferents.  3000 mg/mL acetaminophen (measured in the presence of 5 mM glucose) produced no detectable signal at Navigator, compared with an interference of 140% (or signal equivalent to an additional 7mM glucose) at the conventional sensor. 
  2. Navigator’s calibration curves pass through the origin, with no detectable intercept.  In contrast, a conventional subcutaneous electrochemical sensor gave an intercept (signal at zero glucose concentration) equal to about 2 mM glucose.  Navigator’s low intercept leads to increased accuracy in measurement of very low glucose values, as described in a recent comparative study1of patients with Type 1 diabetes, who underwent hyperinsulemic clamps, while simultaneously wearing both Navigator and a conventional transcutaneous glucose sensor.  During hypoglycemia, 82.4% of Navigator readings were judged accurate; while 61.6% of the readings from the conventional sensor were found to be accurate (p<0.0005).

The performance of the Navigator system was recently tested in clinical trials on subjects with Type 1 diabetes.  In the phase II (accuracy) trial, 58 subjects wore 116 sensors (one sensor each on arm and abdomen) for 120 hours.  Performance was assessed by venous blood glucose measurements taken at 15 minute intervals for 50 of the 120 hours.  A total of 20,362 venous/subcutaneous data pairs were obtained, resulting in a mean absolute relative difference (MARD) of 12.8%.  Data were also evaluated using the Clarke error grid, as follows.

Grid Region

A

B

C

D

E

Overall

MARD

81.7%

16.7%

0.1%

1.6%

0.01%

100%

n

16627

3398

19

316

2

20362


“Holographic Optical Trapping for as a Driver for Measuring Physiological Response”

Kenneth Bradley

Vice-President, Development

Haemonetics Corporation

Optical trapping is a technique that employs forces imposed using light to control biological systems and other material in the microscopic and nanoscopic size ranges.  Recently, this technique has been significantly extended by the development of Holographic Optical Trapping (HOT).  The implementation of diffractive optics in optical trapping systems eliminates moving parts and the bulky physical optics used in traditional optical trapping.  In addition, compared to tradition optical trapping, HOT vastly increases the number of simultaneous interactions under experimental control which allows for new means of exciting and then measuring molecular interactions.  The development of in vitro platforms for diagnostic measurements is a precursor to in vivo monitoring systems.

WPI Technology Presentations

“Extracting Neuromuscular Information from the Electrical Activity of Skeletal Muscle”

Edward (Ted) A. Clancy

Associate Professor

Department of Electrical and Computer Engineering

Department of Biomedical Engineering

Worcester Polytechnic Institute

When skeletal muscles in the body contract, they emit pulses of electrical activity reflecting a set of control commands generated by the central nervous system.  This electrical activity, or electromyogram (EMG), can be observed non-invasively by electrodes placed on the surface of the skin or invasively by electrodes inserted into the muscle.  Two general recording apparatus — and related analysis methods — are used to analyze the EMG.  First, larger surface electrodes can be used which simultaneously record the activity of many underlying muscle fibers.  In this case, the pulses form a stochastic interference pattern whose intensity grows with muscular effort.  Individual pulses become indistinguishable.  Methods for optimally estimating the muscle intensity level (a.k.a. “EMG amplitude”) have application in the control of powered prosthetic limbs, and in estimation of joint torque and (mechanical) impedance for ergonomic and scientific studies.  The second recording/analysis technique is to use small electrodes that are capable of recording the individual pulse activity.  Historically, such recordings required invasive needle or wire electrodes, which can be uncomfortable for the patient/subject.  However, high-resolution surface array electrodes have recently emerged as a potential alternative to invasive recordings.  These recordings provide information on the neural control of muscular activation as well as on peripheral changes/anomalies in neuromuscular transmission and muscle action potential conduction.  Our efforts in these areas will be described.

“Simplicity Noninvasive Glucose Monitor”

Robert A. Peura, Ph.D.

Professor of Biomedical Engineering

Worcester Polytechnic Insititute

We have developed a handheld noninvasive blood glucose meter.  It is easy to use, small in size (17x10x3 cm), and weighs only 0.4 kg. It is a precursor of a commercial meter intended for home use.

It takes ~20 seconds for the instrument to perform a discrete near-infrared optical measurement on the skin, without any irritation or discomfort to the patient.  Due to its fast and noninvasive operation, the device has the potential to be used either for single measurements or for quasi-continuous monitoring. 

Our largest preclinical studies on over 20 subjects (>3,000 data points) have shown that our prototypes have acceptable reliability and can provide results comparable in accuracy to home-use finger stick meters.  Preliminary tests (9 subjects, 539 data pairs) with our newest and most advanced prototype monitor yielded an accuracy of 11.8% (Mean Average Relative Difference) when referenced to the HemoCue clinical blood glucose meter (accuracy of +/- 3.5%).

Our success is based upon the use of the proprietary Optical BridgeTM (OB). The OB method differs from conventional spectrophotometric approaches in that it measures minute alterations in the differential optical absorption of a sample.  These alterations are induced by displacement and re-entry of glucose dissolved in blood in the sampling site.  The OB performs differential measurements with a wavelength pair. During the initial stage of each measurement the wavelength pair is tuned for minimum sensitivity for the background, thus maximizing the relative contribution of glucose in the signal.

This work was supported by NIH grants 2 R44 DK057362-02, 2 R44 DK059088-02 and 2 R44 DK072654-02.

“A Microfluidic Sensor Platform”

Christopher L. Lambert, Ph.D.

Research Associate Professor

Bioengineering Institute

Worcester Polytechnic Institute

Through the combination of microfluidics, self assembled monolayer (SAM) chemistry and the transduction techniques of fluorescence, electrochemistry and surface plasmon resonance (SPR), a microfluidic sensor platform has been realized that is capable of monitoring nanoliter samples.  The device is capable of monitoring potassium, ammonium and lithium ions, it can detect the hybridization of nucleic acids and the pH of a sample over a wide range.  By incorporating a simultaneous transduction measurement the device will be self calibrating and capable of indicating false positive readings.

“Design and Applications of Mobile Ultrasound Imaging System”

Peder C. Pedersen, Ph.D.

Professor

Dept. of Electrical and Computer Engineering
Worcester Polytechnic Institute

Diagnostic ultrasound is today employed across all medical specialties, especially in cardiology, obstetrics, vascular studies and oncology. Ultrasound has found applications in physiological monitoring related to diabetes as well, such as in ophthalmology (detached retina), vascular studies (tissue perfusion) and cardiovascular (arterial stenosis).

The ultrasound research at WPI has been primarily geared towards technologies that enable treatment at point-of-care and with support for clinical personnel with less training in diagnostic ultrasound. Towards that end, we have developed mobile ultrasound systems suited for outdoors as well as indoors situations. Specifically, we are developing a versatile imaging platform for military medicine, general emergency, trauma and disaster, and rural health. This ultrasound system will offer telepresence, in the form of wireless ultrasound image streaming and two-way voice capabilities from disaster site to field hospital or emergency room, it will allow easier diagnostic decisions through 3D imaging and computer aided image analysis for trauma, and it will offer interactive touch screen and will incorporate examination camera and physiological sensors. This effort is augmented with the development of an effective interactive ultrasound training system.

“Wearable Wireless Reflectance-Mode Pulse Oximeter”

R. James Duckworth, Ph.D.

Associate Professor

Department of Electrical & Computer Engineering

Worcester Polytechnic Institute

A wireless wearable pulse oximeter based on a small forehead-mounted optical reflectance sensor has been developed by Professors Mendelson (Biomedical Engineering Dept) and Duckworth (Electrical and Computer Engineering Dept). The battery-operated device can operate for several days. It employs a lightweight sensor comprised of a large area photodetector to reduce power consumption. Dedicated signal processing algorithms are utilized to reduce the effects of motion artifacts. The system also has short range wireless communication capabilities to transfer arterial oxygen saturation, heart rate, respiration rate, body acceleration, and posture information to a PDA or to a USB-based receiver for connection to a PC that can be carried by military and civilian first responders. The system can be programmed to alert on alarm conditions, such as sudden trauma, or physiological values out of their normal range. It also has the potential for use in combat casualty care, such as for remote triage, and for use by first responders, such as firefighters.

This research is funded by the USAMRMC through the Telemedicine and Advanced Technology Research Center (TATRC) and is focused on the development of wearable, wireless, noninvasive physiological monitoring of soldiers, firefighters, and mass casualties.

 

Abstracts/Presentations | Speaker Bios

Maintained by webmaster@wpi.edu
Last modified: February 20, 2008 14:08:48
Maintained by webmaster@wpi.edu
Last modified: February 20, 2008 14:08:48