MULTIPLEXING OF AUDIO
AND MEDICAL SIGNALS FOR
EMERGENCY RADIO COMMUNICATION SYSTEM

Koichi Shimizu, Seiji Matsuda and Katsuyuki Yamamoto
Department of Bioengineering, Graduate School of Engineering,
Hokkaido University, Sapporo, 060, Japan

INTRODUCTION In order to improve the emergency care in an ambulance, a paramedic system has been legislated in Japan. However, the paramedic can perform advanced 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.

METHOD Fig.1 illustrates the principle of biotelemetry from a moving ambulance. A frequency-division multiplexing technique was applied to the simultaneous transmission of the audio and medical data using a single radio channel. The audio signal is allocated in the range of 0.3-1.1 kHz, and the medical data, in the range of 2.0-2.8 kHz.

EXPERIMENTS AND RESULTS First, the practical feasibility of this technique was examined by measuring the understandability of monosyllables, words and sentences. The result was satisfactory for practical use. Then, 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 a high-frequency component, the quality of vocal communication was satisfactory for emergency practice. The waveforms of ECG signal 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 allow us effective emergency diagnosis and treatment before hospital arrival with the currently used communication link without adding another channel.