Multiplexing Technique of Audio and Medical Signals for Emergency Radio

In order to improve the emergency care in an ambulance, a paramedic system has been legislated. However, the paramedic can perform significant emergency care, only when the concrete instructions from a medical doctor are available. To operate this system effectively, a telemetry system was developed which transmits audio and medical signals from an ambulance to a medical doctor in a hospital. It also transmits the vocal instruction of the doctor from the hospital to the ambulance. A frequency-division multiplexing technique was applied to the simultaneous transmission of the audio and medical data using a single radio channel. The high-frequency portion of the audio signal is suppressed to be 0.3-1.1 kHz, and the medical data is inserted in the portion, i. e. 2.0-2.8 kHz. An experimental system was developed and the transmission experiments from moving automobile were conducted using a mobile telephone and emergency radio. Even with the lack of high-frequency component, the quality of vocal communication was satisfactory for emergency practice. The waveforms of ECG signals were also satisfactory for emergency diagnosis and monitoring, even when the condition of radio transmission was degraded in normal condition. When the audio and medical data were transmitted simultaneously, there was no interference observed. This technique will allows us effective emergency diagnosis and treatment before hospital arrival with the currently used communication link without adding another channel.