Detecting daily activity of solitary living elderly persons.

We report on an activity monitoring system for elderly persons living alone. Caregivers would like to know whether the person is talking during their daily activity. Our monitoring system consists of a recorder and a personal computer. The recorder, attached to the subject's chest, employs two microphones, a tri-axis accelerometer, two low-power amplifiers, a low-power microcomputer (MC) and a 2GB micro SD Memory Card (SDMC). One of the microphones is set in the direction of the chest for recording the person's voice, and the other microphone is set to the opposite side for recording surrounding sound. The microphone outputs and the accelerometer outputs are sent to the MC’s 10 bit analog to digital converters and sampled at 4000Hz and 50Hz, respectively. The MC detects the length of the conversation time from the microphone outputs, and the posture and behavior are detected from the accelerometer outputs every 5 seconds. The detected time, posture and behavior are stored in the SDMC. The data can be downloaded from the memory card and sent to appropriate stations. The system is used to monitor the health and physical conditions during daily life of elderly persons living alone.

An ultrasonic stride length measuring system employing two digital compasses.

We have developed an ultrasonic stride length measuring system for analyzing the human gait. All elements of the system are quite small and each fit into an appropriate package. An ultrasonic transmitter, a digital compass, a radio transmitter and a microcontroller are attached to the subject’s heel on the right shoe and in the direction of the left shoe. Two ultrasonic receivers, a digital compass, a radio receiver, a microcontroller and a 1GB SD memory card are installed on the left shoe. The ultrasonic receivers are attached to the toe and heel in the direction of the right shoe. The walking direction is thus detected by the compass attached on the right and left shoes, respectively. The stride length is detected by the difference between the radio wave and ultrasonic propagation velocities. The stride length is corrected by the detected walking direction, and then the corrected stride length is stored in the SD memory card. When downloaded, the memory card gives the accurate stride length which then is used to characterize the subject’s gait during daily activity.

An ultra flexible capacitive electrode for an ecg recording system - biomed 2013.

We have developed an ultra-flexible skin electrode to monitor a patient’s electrocardiogram (ECG) during daily activity. This electrode consists of a 1.5 micrometer thick polyester film printed with electro-conductive paint. The electrode is attached to the outside of a polyethylene bag filled with a high viscoelastic fluid. When the electrode is placed securely on the skin, it correspondingly changes its shape, and electrode movement artifact is thereby decreased. The electrode improves long-term recording of the ECG by maintaining capacitance-coupled impedance between the electrode and the skin.

An electronic communication system for amyotrophic lateral sclerosis patients - biomed 2013.

Amyotrophic lateral sclerosis is a progressive degeneration of motor neurons. Patients with the disease lose their ability to speak and to use their hands as the disease progresses. We have developed a new electronic communication system that enables communication by blinking of the eyes. The system consists of a light emitting diode (LED), two silicone rubber electrodes, an electrooculogram (EOG) recorder, a microcontroller, a sound reproduction board, a pillow speaker and a low power mobile phone. The two silicone rubber electrodes record the EOG induced by blinking the eyes synchronized with LED flashing. The EOG is amplified by the EOG recorder. The microcontroller detects the blinking from the amplified EOG, and then their meanings are confirmed by voice. After that, the patient’s intention is transmitted to the nurse by a low power mobile phone so the care giver is kept in the loop.

An updated and more accurate drip infusion solution monitoring system - biomed 2013.

We have developed a drip infusion solution monitoring system for hospital and care facility use that is much more accurate than our previous reported system. The system consists of two electrodes and an acceleration sensor. The electrodes, which are wrapped around the infusion supply polyvinyl chloride (PVC) tube from the solution bag and the drip chamber, measure the growth and fall of each drop of infusion solution. The drip rate is detected from the fall of each drop. In addition, the acceleration sensor is attached to the outside of the drip chamber and detects the tilt angle of that chamber. The injected infusion solution amount is calculated by the infusion solution quantity per one drop and the drip rate. However, the quantity changes depend on the tilt angle of the drip chamber. The quantity of each drop is then corrected by the tilt angle of the drip chamber.

A new ultrasonic stride length measuring system.

We have developed a new ultrasonic stride length measuring system for analyzing the human gait. An ultrasonic transmitter, a radio transmitter, a pressure sensor and microcontroller are attached to the subject’s heel on the right shoe and in the direction of the left shoe. Two ultrasonic receivers, a radio receiver, a microcontroller and a 1GB SD memory card are installed on the left shoe. Ultrasonic receivers are attached to the toe and heel, in the direction of the right shoe. When the right foot contacts the ground, its heel-mounted ultrasonic and radio transmitters simultaneously transmit to the left shoe. However, radio propagation velocity is far faster than ultrasonic velocity. Therefore, the radio wave acts as a start signal to the radio receiver of the left shoe, indicating the start of ultrasound transmission from the right shoe. Upon receiving the start signal, the microcontroller timer starts to measure each ultrasound propagation time from the right shoe to the left shoe. Distance between right and left shoes is calculated with the time and ultrasound velocity and stored in the SD memory card. Stride length is calculated with a cosine function, by using the obtained distances and the distance between the toe and heel of the left shoe, by a conventional computer. The stride length can then be used for many characterizations of the subject’s gait.

A drip infusion warning system.

We have developed a drip infusion warning system for hospital and care facility use. In general, two kinds of infusion sets are used, which have drop factors of either 20 or 60. (A drop factor is the number of drops to deliver 1 ml of infusion solution.) When an infusion set having a 20 drop factor is used, the number of drops per drip is adjusted to 20. If an infusion set has a drop factor of 60, then the infusion volume rate becomes three times as much. This may result in legal consequences if the patient is injured. In this study, a drip infusion warning system detects whether the infusion is a 20 or a 60 drop factor. The system consists of two electrodes, one wrapped around the infusion supply polyvinyl-chloride tube, and another one around the drip chamber. The electrical impedance between two electrodes is changed by the growth and fall of each drop of fluid. The drop growth length especially changes, depending on the type of infusion set used. Therefore, the two types of infusion sets can be identified by monitoring the drop length. Our warning system detects whether the infusion set used corresponds to a 20 or 60 drop factor, so the system can reduce human errors.

A remote drip infusion monitoring system employing Bluetooth.

We have developed a remote drip infusion monitoring system for use in hospitals. The system consists of several infusion monitoring devices and a central monitor. The infusion monitoring device employing a Bluetooth module can detect the drip infusion rate and an empty infusion solution bag, and then these data are sent to the central monitor placed at the nurses' station via the Bluetooth. The central monitor receives the data from several infusion monitoring devices and then displays graphically them. Therefore, the developed system can monitor intensively the drip infusion situation of the several patients at the nurses' station.

Relationship between frequency and impedance change in an infusion rate measurement system employing a capacitance sensor - biomed 2011.

We have been searching for a suitable frequency range for an electrical impedance measurement infusion solution drip monitoring system, which we have previously reported. This electrical impedance, which is formed between two electrodes wrapped around the infusion supply polyvinyl-chloride tube and around the drip chamber, is changed by the growth and fall of each drop of fluid. Thus, the drip rate can be detected by measuring this impedance. However, many different kinds of infusion solutions such as glucose, amino acid, soya oil, and lactated Ringer’s solution are used in hospitals and care facilities. Therefore, it was necessary to find a suitable frequency for driving the capacitance-change sensor with a wide range of infusion solutions. In this study, the sensor electrical impedance change of 16 infusion solutions was measured from 1 kHz up to 1 MHz. The drip impedance produced by 5% glucose solution, 10% glucose solution and soya oil indicated the maximum sensor output change at 10 kHz, 20 kHz, and 70 kHz, respectively. The other 13 infusion solutions increased up to 10 kHz, and were constant from 10 kHz to 1 MHz. However, the growth, fall, and drip rate of the drops of all the infusion solutions were monitored by measuring the impedance change from 10 kHz to 30 kHz. Our experimental results indicated that most suitable excitation range for the infusion monitoring system is from 10 kHz to 30 kHz. Thus, we can now “fine-tune” the system for optimal sensing.

A mobile phone-based ecg and heart sound monitoring system - biomed 2011.

We have developed a telemedicine system to monitor a patient’s electrocardiogram (ECG) and heart sounds (PCG) during daily activity. The complete system, consisting of an ECG recorder, an accelerometer and a 2.4 GHz low power mobile phone, is mounted on three chest sensing electrodes. The accelerometer records the PCG produced by closing of the mitral and aortic valves (S1 and S2). The sampled ECG and PCG are stored in the system for two minutes and continuously updated. When a patient feels heart discomfort such as angina or an arrhythmia, he/she pushes the data transmission switch on the system. The ECG and PCG for the next two minutes are stored in the system, and then the system then sends the four minutes of stored data directly to a hospital server computer via the 1.9 GHz low power mobile phone. These data are stored on the server and then downloaded to the physician’s Java configured mobile phone. The physician can then check the patient’s cardiac condition, regardless of patient or physician locations, and then take appropriate actions.

A new safety support system for wandering elderly persons.

We have developed a new mobile phone-based safety support system for transmitting information of a wandering elderly person's location and the environmental sounds around that person. The system consists of a wearable sensor and a conventional desktop PC with Internet access acting as the server computer. The wearable sensor, which is attached behind the neck of the elderly person's shirt, is composed of a low transmitting power mobile phone (W-SIM), a small microphone and a one chip microcontroller. The wandering elderly person's location is identified within 100 m from the mobile phone company's antenna ID via the W-SIM. The caregiver sets the elderly person's movement area by specialized computer software. When the elderly person goes out of the area, the sensor automatically records the environmental sound around the wandering elderly person for the presumption of the person's situation with the small microphone. The W-SIM sends both the wandering elderly person's location and the environmental sound to the server computer. The server computer informs automatically the caregiver by the e-mail. The caregiver can monitor the sound and the map of the wandering person's location via Internet. The sound enables the presumption of an accurate location and the situation of the wandering elderly person.

A sensor for monitoring pulse rate, respiration rhythm, and body movement in bed.

A non-constraint cardiac vibration, respiration, and body movement monitoring system has been developed. The sensor system is designed to be easily installable under an existing bed mattress. The sensor consists of a 40-kHz ultrasound transmitter and receiver pair. The transmitted ultrasound is reflected on the mattress' undersurface, and the amplitude of the received ultrasonic wave is modulated by the shape of the mattress, and parameters such as respiration, cardiac vibration, and movement. The physiological parameters can be extracted from the reflected ultrasound by an envelope detection circuit. To confirm the accuracy of the developed system, measurements were performed on 6 normal male subjects aged 25.0 ± 6.7 years, using 2 pocket spring coil mattresses and a polyurethane foam mattress. The results revealed that the physiological parameters were monitored with an 84.2% average accuracy for all mattresses when the subjects lay on the beds in the supine, lateral, and prone positions.

A daily living activity remote monitoring system for solitary elderly people.

A daily living activity remote monitoring system has been developed for supporting solitary elderly people. The monitoring system consists of a tri-axis accelerometer, six low-power active filters, a low-power 8-bit microcontroller (MC), a 1GB SD memory card (SDMC) and a 2.4 GHz low transmitting power mobile phone (PHS). The tri-axis accelerometer attached to the subject's chest can simultaneously measure dynamic and static acceleration forces produced by heart sound, respiration, posture and behavior. The heart rate, respiration rate, activity, posture and behavior are detected from the dynamic and static acceleration forces. These data are stored in the SD. The MC sends the data to the server computer every hour. The server computer stores the data and makes a graphic chart from the data. When the caregiver calls from his/her mobile phone to the server computer, the server computer sends the graphical chart via the PHS. The caregiver's mobile phone displays the chart to the monitor graphically.

A system for monitoring cardiac vibration, respiration, and body movement in bed using an infrared.

We have developed a non-invasive system for monitoring cardiac vibrations, respiration and body movement of in-bed hospitalized patients and elderly people who need constant care. These physiological parameters are recorded by an infrared emitting diode and a photo transistor, which are attached between spring coils in bed mattress. The infrared emitting diode diffuses infrared light into the mattress. The diffusion of this energy is changed by mattress shape variations and spring coil vibrations, which modulate the intensity of the received infrared signal. The intensity is also modulated by physiological parameters such as heart pulse, respiration and body movement. The physiological parameters are detected from the received infrared intensity signal by low, high and band pass filters.

A new drip infusion solution monitoring system with a free-flow detection function.

A new drip infusion solution monitoring system has been developed for hospital and care facility use. The system detects the fall of each drip chamber drop of fluid and also a free-flow situation. Three non-contacting copper foil electrodes are used. The electrodes are wrapped around the infusion supply polyvinyl chloride (PVC) tube from the solution bag, the drip chamber, and the infusion PVC tube from the drip chamber. Drip infusion fluids have electrical conductivity, so a capacitor is formed between the infusion fluid and each electrode. A thirty kHz sine wave is applied to the electrode wrapped around the infusion supply PVC tube from the solution bag. The capacity-coupled signal on the drip chamber electrode is the transducer output. When an infusion fluid drop is forming, its length and diameter, and therefore the drip chamber capacitance, are increasing, causing change in the output signal. The drip chamber electrode can detect the fall of each drip chamber drop of fluid. When the infusion solution becomes free-flow, an infusion fluid drop is not forming and the infusion fluid flows continuously. Therefore, the capacitance of the electrode around drip chamber does not change the output signal. On the other hand, the electrode wrapped around the infusion supply polyvinyl chloride tube under the drip chamber detects the thirty kHz sine wave conducted by the infusion fluid. The drip chamber electrodes and the infusion supply PVC tube under the drip chamber detect each drop of fluid and free-flow, respectively.

Monitoring respiration and body movement in the home bathrooms - biomed 2010.

We have developed a non-intrusive safety monitoring system which can measure respiration and body movements of solitary-living elderly people while they are in their home bathroom. These physiological variables are monitored with a 40 kHz ultrasonic transmitter and four receivers. The ultrasonic transmitter diffuses an ultrasonic wave throughout the room. The diffusion pattern of this inaudible sonic energy is changed by body movements and respiration, therefore modulating the amplitude of the received ultrasonic signal. The received ultrasonic signals are demodulated by envelope detection circuits. Band-pass filters detect respirations and body movements from the envelope detection circuit outputs. These detected signals are added and used to monitor whether the elderly person is safe or not safe, while in their bathroom. When the microcomputer cannot detect body movement or respiration, it alerts the persons caregiver, via a low power personal handy phone system.

Physiological and care monitoring of anti-decubitus mattress patients - biomed 2010.

UNLABELLED: An ultrasonic physical and care monitoring system has been developed for monitoring the physiological parameters of body movement, heart contraction, and respiration of patients on low-repulsion, anti-decubitus (anti-bedsore) hospital beds. These beds, of several designs, are intended to reduce pressure on the body surface of immobilized patients, in order to prevent decubitus ulcers, which are often fatal. Since low-repulsion mattresses lack conventional springs, padding and air space, this system employs a polyvinyl chloride tube under the mattress, which has a 40 kHz ultrasonic transmitter and receiver at its ends. The shape of the tube is altered by body, heart and respiratory movements, which modulate the complex diffusion of the ultrasonic energy in the tube. As a result, the amplitude of the received ultrasonic signal is movement-modulated. This received signal is then demodulated and low, high and band pass filtered, to yield the three separate patient movement parameters. These are recorded and can be real-time computer analyzed, to activate alarms if the patient has not moved, or not been moved by the staff, within programmable time limits. These data may also be employed to indicate relative patient medical condition. A major system advantage is that it does not require any body-attached sensors. KEYWORDS: Ultrasound, cardiac pulse, respiration, body movement, low-repulsion mattress, decubitus ulcer.

A new drip infusion monitoring system - biomed 2010.

A new drip infusion solution monitoring system has been developed for hospital and care facility use. The system detects and counts the fall of each drip chamber drop of fluid. Two non-contacting copper foil electrodes are used; one wrapped around the infusion supply polyvinyl-chloride tube under the solution bag and another around the drip chamber, forming two capacitors. Drip infusion fluids have electrical conductivity, so the capacitors are a series-connected electrical impedance. A thirty kHz sine wave is applied to the infusion tube electrode and the capacity-coupled signal on the drip chamber electrode is the transducer output. When an infusion fluid drop is forming, its diameter, and therefore drip chamber capacitance, are increasing, causing change in the output signal. When the drop reaches sufficient diameter to fall, the drip chamber capacitance decreases, which briefly returns the output signal to baseline. Therefore, the growth, fall, and drip rate of each drop of fluid can be detected from the output signal waveform. The system also has advantages of being insensitive to ambient light type and intensity, and detects when the infusion bag is empty.

A new bed-exiting alarm system for welfare facility residents.

A newly developed alarm system detects welfare facility residents leaving their beds, and does not respond to the care staff, who wear shoes or slippers. It employs a stainless steel tape electrode, several linear integrated circuits and a low-power 8-bit single chip microcomputer. The electrode, which is used as a bed-exiting detection sensor, is attached to the floor mat to record changes in the always-present AC (alternating current) voltage induced on the patient's body by electrostatic coupling from the standard 100 volt, 60 Hz AC utility power wiring in the room walls and ceiling. The resident's body movements, before trying to get out of bed and after leaving the bed, are detected by the microcomputer from changes in the induced AC voltage. The microcomputer alerts the care staff station, via a power line communication system or PHS (personal handy phone System).

A wireless breathing-training support system for kinesitherapy.

We have developed a new wireless breathing-training support system for kinesitherapy. The system consists of an optical sensor, an accelerometer, a microcontroller, a Bluetooth module and a laptop computer. The optical sensor, which is attached to the patient's chest, measures chest circumference. The low frequency components of circumference are mainly generated by breathing. The optical sensor outputs the circumference as serial digital data. The accelerometer measures the dynamic acceleration force produced by exercise, such as walking. The microcontroller sequentially samples this force. The acceleration force and chest circumference are sent sequentially via Bluetooth to a physical therapist's laptop computer, which receives and stores the data. The computer simultaneously displays these data so that the physical therapist can monitor the patient's breathing and acceleration waveforms and give instructions to the patient in real time during exercise. Moreover, the system enables a quantitative training evaluation and calculation the volume of air inspired and expired by the lungs.