Emil Valchinov

Design and testing of low intensity laser biostimulator.

BackgroundThe non-invasive nature of laser biostimulation has made lasers an attractive alternative in Medical Acupuncture at the last 25 years. However, there is still an uncertainty as to whether they work or their effect is just placebo. Although a plethora of scientific papers published about the topic showing positive clinical results, there is still a lack of objective scientific proofs about the biostimulation effect of lasers in Medical Acupuncture. The objective of this work was to design and build a low cost portable laser device for stimulation of acupuncture points, considered here as small localized biosources (SLB), without stimulating any sensory nerves via shock or heat and to find out a suitable method for objectively evaluating its stimulating effect. The design is aimed for studying SLB potentials provoked by laser stimulus, in search for objective proofs of the biostimulation effect of lasers used in Medical Acupuncture.MethodsThe proposed biostimulator features two operational modes: program mode and stimulation mode and two output polarization modes: linearly and circularly polarized laser emission. In program mode, different user-defined stimulation protocols can be created and memorized. The laser output can be either continuous or pulse modulated. Each stimulation session consists of a pre-defined number of successive continuous or square pulse modulated sequences of laser emission. The variable parameters of the laser output are: average output power, pulse width, pulse period, and continuous or pulsed sequence duration and repetition period. In stimulation mode the stimulus is automatically applied according to the pre-programmed protocol. The laser source is 30 mW AlGaInP laser diode with an emission wavelength of 685 nm, driven by a highly integrated driver. The optical system designed for beam collimation and polarization change uses single collimating lens with large numerical aperture, linear polarizer and a quarter-wave retardation plate. The proposed method for testing the device efficiency employs a biofeedback from the subject by recording the biopotentials evoked by the laser stimulus at related distant SLB sites. Therefore measuring of SLB biopotentials caused by the stimulus would indicate that a biopotential has been evoked at the irradiated site and has propagated to the measurement sites, rather than being caused by local changes of the electrical skin conductivity.ResultsA prototype device was built according to the proposed design using relatively inexpensive and commercially available components. The laser output can be pulse modulated from 0.1 to 1000 Hz with a duty factor from 10 to 90 %. The average output power density can be adjusted in the range 24 – 480 mW/cm2, where the total irradiation is limited to 2 Joule per stimulation session. The device is controlled by an 8-bit RISC Flash microcontroller with internal RAM and EEPROM memory, which allows for a wide range of different stimulation protocols to be implemented and memorized. The integrated laser diode driver with its onboard light power control loop provides safe and consistent laser modulation. The prototype was tested on the right Tri-Heater (TH) acupuncture meridian according to the proposed method. Laser evoked potentials were recorded from most of the easily accessible SLB along the meridian under study. They appear like periodical spikes with a repetition rate from 0.05 to 10 Hz and amplitude range 0.1 – 1 mV.ConclusionThe prototypes specifications were found to be better or comparable to those of other existing devices. It features low component count, small size and low power consumption. Because of the low power levels used the possibility of sensory nerve stimulation via the phenomenon of shock or heat is excluded. Thus senseless optical stimulation is achieved. The optical system presented offers simple and cost effective way for beam collimation and polarization change. The novel method proposed for testing the device efficiency allows for objectively recording of SLB potentials evoked by laser stimulus. Based on the biopotential records obtained with this method, a scientifically based conclusion can be drawn about the effectiveness of the commercially available devices for low-level laser therapy used in Medical Acupuncture. The prototype tests showed that with the biostimulator presented, SLB could be effectively stimulated at low power levels. However more studies are needed to derive a general conclusion about the SLB biostimulation mechanism of lasers and their most effective power and optical settings.

Wearable Wireless Biopotential Electrode for ECG Monitoring

A single channel wearable wireless ECG biopo- tential electrode is presented. The device is built up of com- mercial components and utilizes 434 MHz license free fre- quency band. The three electrode, two-stage biopotential amplifier design and the wireless signal transfer system, yielded very low noise and excellent interference rejection. A CMRR of 100 dB at 50 Hz and an equivalent input voltage noise of 0.4 μVrms were measured during the tests of the de- veloped prototype. The amplified analog ECG signal is sam- pled with 500 Hz by a 10 bit Analog-to-Digital Converter (ADC) and transmitted via UHF Amplitude-Shift Keying transmitter to a dedicated receiver module USB connected to a PC. Both the ADC and RF-transmitter are embedded in the flash-based 8-bit CMOS Microcontroller rfPIC12F676F. The receiver module is based on the low cost single conversion superheterodyne receiver rfRXD0420, interfaced with an 8-bit CMOS microcontroller PIC16C745 with USB support. The developed electrode is powered by a small coin cell lithium battery and can perform continuous ECG recording and transmission for more than a week.

Wearable ECG system for health and sports monitoring

A wireless ECG system using dry-contact electrodes is presented. The system consists of a pair of coin sized dry-contact electrodes manufactured on a standard printed circuit board that can operate both on top of the skin and through clothing and can be embedded within comfortable layers of fabric. The wireless main unit assures the transmission of the ECG signal to a computer for storage and processing. The system provides a differential gain of 56dB over a 1–150Hz bandwidth. Signals are digitized with a 10-bit ADC and samples are transferred via ultra-low power ANT+ wireless technology. The preliminary results showed that the proposed wearable system is ideally suited for monitoring patient cardiac activity in real time at home, healthcare or sports facilities. It is highly suitable for integration in wearable ECG chest harness.

A wearable wireless ECG sensor: a design with a minimal number of parts

A wearable wireless sensor for ECG monitoring is presented. It features a split design where the digital and the analog part of the sensor are separated self-contained subparts. The radio link is implemented with an ZigBit module compatible with robust IEEE 802.15.4/ZigBee stack for wireless personal area networks (WPANs). A two-way wireless data transmission link operating at license free 2.4 GHz frequency band is used for transferring the 10-bit measurement data to a receiver device connected to a PC. Tailored PC software is used for displaying the signals and controlling the measurement parameters. The ECG sensor is aimed for measurements in patient’s natural living environment during daily routines and continuous long term measurement for people having, or being recovering from a cardiac disease. The ECG sensor can operate alone or it can be used as a part of wireless personal area network in health care facilities.

Advanced observation and telemetry heart system utilizing wearable ECG device and a Cloud platform

Short lived chest pain episodes of post PCI patients represent the most common clinical scenario treated in the Accidents and Emergency Room. Continuous ECG monitoring could substantially diminish such hospital admissions and related ambulance calls. Delivering community based, easy-to-handle, easy to wear, real time electrocardiography systems is still a quest, despite the existence of electronic electrocardiography systems for several decades. The PATRIOT system serves this challenge via a 12-channel, easy to wear, easy to carry, mobile linked, miniaturized automatic ECG device and a Cloud platform. The system may deliver high quality electrocardiograms of a patient to medical personnel either on the spot or remotely both in a synchronous or asynchronous mode, enhancing autonomy, mobility, quality of life and safety of recently treated coronary artery disease patients.

Real-Time Detection of Pathological Cardiac Events for a Wearable Wireless ECG Monitor

Wearable wireless ECG monitors have the potential of monitoring the cardiac function without restricting patients’ freedom of movement. However, due to their reduced size and consequent limited computational resources, they require the development of dedicated algorithms for real-time ECG signal processing. The paper reports a real-time algorithm based on heuristic methods for detecting pathological cardiac events from the ECG signal captured by a wearable wireless ECG sensor developed by the University of Patras. The algorithm parameter optimization is also described, as well as the performance evaluation with the MIT-BIH Arrhythmia Database, for which Se=95.92% and Sp=98.24% were obtained.