A remote monitor of bed patient cardiac vibration, respiration and movement

Abstract

We have developed a remote system for monitoring heart rate, respiration rate and movement behavior of at-home elderly people who are living alone. The system consists of a 40 kHz ultrasonic transmitter and receiver, linear integrated circuits, a low-power 8-bit single chip microcomputer and an Internet server computer. The 40 kHz ultrasonic transmitter and receiver are installed into a bed mattress. The transmitted signal diffuses into the bed mattress, 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 modulated ultrasonic signal is received and demodulated by an envelope detection circuit. Low, high and band pass filters separate the respiration, cardiac vibration and movement signals, which are fed into the microcontroller and digitized at a sampling rate of 50 Hz by 8-bit A/D converters. The digitized data are sent to the server computer as a serial signal. This computer stores the data and also creates a graphic chart of the latest hour. The person's family or caregiver can download this chart via the Internet at any time.

Non Contact Heart Monitoring

“…A simpler approach is reported for measuring the physiological parameters, using an ultrasonic sensing of heart and respiration rate and movement behavior, developed for elderly people which are in bed. Bed structure oscillations due to the respiration and heart pulses are detected using an ultrasonic transmitter and an ultrasonic receiver installed in both sides of the bed rail (Mukai et al, 2009). When a person is lying in any position, on any bed area, then his/her physiological parameters alter the shape of the mattress and amplitude modulate the received signal.…”

Non contact monitoring of the respiration activity by electromagnetic sensing.

“…At the moment arterial pressure and oxygen saturation are still measureable only with contact, even if indirect measurement of these quantities are possible without direct contact with patient blood [15][16][17]. For what concern respiration monitoring, the scientific literature [18][19][20][21] and market solutions propose under-the-mattress transducers for the individuation of apnea events in infants or chest belt to be applied around the patient thorax. These devices are mainly used for monitoring and sleep disorders diagnosis.…”

Evaluation of Ultrasound-Based Sensor to Monitor Respiratory and Nonrespiratory Movement and Timing in Infants

“…Non-contacting methods are useful when no contact is desired or possible. These include the use of pressure mattresses [1], radar [2], infrared imaging of warm expired gas [3], ultrasound methods of detecting airflow at the face [4], or reflected ultrasound from the underside of a mattress [5]. Non-contacting sensors are especially useful for sleep apnea detection, and have been used in infants for synchronization of a mechanical ventilator with spontaneous breathing efforts even when a patient has an artificial airway or must wear nasal prongs with large leaks in the airway-infant interface [6].…”