Sokwoo Rhee

Mobile monitoring with wearable photoplethysmographic biosensors

We address both technical and clinical issues of wearable biosensors (WBS). First, design concepts of a WBS are presented, with emphasis on the ring sensor developed by the authors group at MIT. The ring sensor is an ambulatory, telemetric, continuous health-monitoring device. This WBS combines miniaturized data acquisition features with advanced photoplethysmographic (PPG) techniques to acquire data related to the patients cardiovascular state using a method that is far superior to existing fingertip PPG sensors. In particular, the ring sensor is capable of reliably monitoring a patients heart rate, oxygen saturation, and heart rate variability. Technical issues, including motion artifact, interference with blood circulation, and battery power issues, are addressed, and effective engineering solutions to alleviate these problems are presented. Second, based on the ring sensor technology the clinical potentials of WBS monitoring are addressed.

The ring sensor: a new ambulatory wearable sensor for twenty-four hour patient monitoring

This paper describes the development of a ring sensor for twenty-four hour patient monitoring. The ring is packed with LEDs and photodetectors where the technology of pulse oximetry is implemented for blood oxygen saturation monitoring. The measured data are transmitted to a computer through a digital wireless communication link. The ring sensor is worn by the patient at all times, hence the health status is monitored 24 hours a day. Detailed descriptions of the hardware and the software of the ring sensor will be presented. Also, the effects of motion artifact and ambient light will be investigated.

A twenty-four hour tele-nursing system using a ring sensor

This paper presents the development of the ring sensor to monitor a patient 24 hours a day for a tele-nursing system. The ring sensor is worn by the patient at all times, hence the health status is monitored 24 hours a day. The sensors packed into the ring include LEDs with different wavelengths, and technologies of photoplethysmography and pulse oximetry are implemented on the ring. The sensor data are transmitted to a computer through the digital wireless communication link and the patient status is analyzed continually and remotely. Any trait of abnormal health status and possible accidents is detected by analyzing the sensor data. A combination of a global receiver and multiple local ones are used to estimate the patients location and activity. Both the physiological data and the position information can be used to make an accurate decision as to whether a warning signal must be sent to a medical professional caring the patient. An issue of power reduction for miniaturization of the ring sensor is also addressed.

Development of the ring sensor for healthcare automation

Abstract This paper presents the development of a miniaturized telemetered ambulatory monitoring device in a ring configuration. The device, called ring sensor, is worn by the patient at all times, hence the health status is monitored 24 hours a day. The ring is equipped with LEDs and photo detectors where the technology of pulse oximetry is implemented for monitoring pulse waves and blood oxygen saturation. The measured data are transmitted to a computer through a digital wireless communication link and the patient health status is analyzed continuously and remotely. Any trait of abnormal health status and possible accidents is detected by analyzing the sensor data. Detailed descriptions of the hardware and the software of the ring sensor including a noise protection algorithm will be presented. Also, unique features of the 24 hour patient monitoring system using the ring sensor will be discussed.

Implementation and validation of a power-efficient, high-speed modulation design for wireless oxygen saturation measurement systems

This paper describes the implementation and initial validation results of a novel power-efficient, high-speed modulation design for wearable oxygen saturation sensor systems. The research presented is in conjunction with the development of continuous photo plethysmographic health monitoring device known as the Ring Sensor. It is demonstrated that a high LED modulation rate coupled with a low duty cycle significantly reduce LED power consumption. Additionally, initial benchmarking results using a Nellcor N-395 pulse oximeter indicate good agreement with the new design for both heart rate and oxygen saturation measurements.

Design of a artifact-free wearable plethysmographic sensor

The ring sensor is a compact, wearable device that was originally designed for continuous physiological monitoring of a human body. In this paper, the authors propose a new design of the ring sensor that can alleviate the artifacts of motion and ambient light significantly.

Modeling of finger photoplethysmography for wearable sensors

This paper describes the development of an optophysiological model of a finger in conjunction with a ring-type photoplethysmography device (the ring sensor). It describes the photoplethysmographic effects due to the relative displacement and rotation of a finger to a ring-type optoelectric device that monitors the arterial pulsation noninvasively and continuously. Numerical simulations and experiments were conducted to verify and evaluate this model.

Integrated computer tools for top-down assembly design and analysis

This paper describes a prototype software system that implements a top-down approach to the concept stage of assembly design and analysis. The software implements a number of concepts and techniques introduced by the authors in previous publications. The study comprises a definition of a top-down approach to assembly design, development of several new assembly analysis and synthesis algorithms, and integration with existing algorithms. New assembly analysis and synthesis tools include: a graphical layout tool for defining an assembly level dimensional control plan, mathematical models of assembly features, assembly constraint analysis, variation propagation analysis in the presence or absence of adjustments, and an optimal control algorithm for assembly feature synthesis. Existing tools include assembly sequence constraint generator and assembly sequence generator-editor. A common assembly database is created that is used by the different analysis tools. Some of the functionalities are still evolving.