An Infant Monitoring System Using CO 2 Sensors Hung Cao, Lun-Chen Hsu, Thermpon Ativanichayaphong, Jeongsik Sin, Harry E. Stephanou and J.-C. Chiao Automation & Robotics Research Institute, The University of Texas at Arlington Abstract— In this paper, we proposed an infant monitoring system to reduce the potential risks for Sudden Infant Death Syndrome (SIDS). This system can be used for infants at home or in a hospital nursery room. The system consists of carbon dioxide (CO 2 ) sensors and active Radio Frequency Identification (RFID) technology. A commercial metal-oxide based CO 2 sensor was chosen and characterized in sensitivity, selectivity and humidity dependence. A proof-of-concept system, to be used for two infants in the same room, was designed and assembled. The RFID transmission was accomplished with a wireless module at two different operating frequencies. The results are promising. A method for further practical applications in a large nursery room is also discussed in details in this paper. Keywords: Infant, SIDS, CO 2 sensor, RFID. I. INTRODUCTION Healthcare cost is an urgent issue globally. In the U.S., the cost for healthcare has reached 16% of the Gross National Product in 2004, equating to US$1.88 trillion [1]. The costs for infant care are high due to the facts that the work is highly labor intensive. For healthy infants, Sudden Infant Death Syndrome (SIDS) is the most critical problem needed to be addressed. SIDS is defined as any sudden and unexplained death of an apparently healthy infant aged one month to one year [2-3]. According to the National SIDS/Infant Death Resource Center, SIDS is responsible for roughly 50 deaths per 100,000 births in the U.S. in 2004 (Fig. 1). Although the SIDS rate has been reducing, due to the awareness in parents and nurses, it is still too high for any family that suffers trauma and loss. Reducing the sudden death rate in infants by an effective monitoring and alarm system is a challenge for researchers. Figure 1. The SIDS rate in the U.S. from 1990 to 2004 [3]. Although the causes of SIDS have not been explained thoroughly in literatures, trouble with breathing has been known as the most common reason. Inborn factors such as disorders in the lungs or glands, respiratory infections, and improper sleeping positions are possible causes [2-3]. SIDS may happen to healthy infants without any identifiable physiological preconditions and it usually happens during sleeping without any warning signs, such as crying, struggling or suffering. Therefore, an effective respiratory monitoring system may be a good way for early warning to reduce SIDS risk. There were some proposed infant monitoring systems, such as cardiopulmonary monitoring [4-7], vision monitoring [8], oxygen consumption monitoring [9] and multi-purpose monitoring [10]. Some approaches are invasive [4-7, 9-10], making both the infant and his/her parents uncomfortable. Some are not as effective as expected such as baby monitoring cameras due to the unrecognized signs of SIDS [8]. We propose a new method using CO 2 sensors placed in the crib around an infant to non-invasively monitor the exhaled air concentration variation from him/her. By monitoring the outputs of CO 2 sensors, we can detect if there is anything wrong with the infant’s respiration. The output data can be used to activate an alarm or logged for further diagnoses. With RFID integration, our system can be used to monitor a large number of infants in the nursery room of a hospital. II. METHODOLOGY A. System design 1) Crib design Infants may take various sleeping positions and the exhaled air may spread in many directions due to air circulation. Thus, an array of CO 2 sensors is placed around the crib on the bars to provide sufficient information. A circuit board connected to the sensors is placed outside the crib to process the data (Fig. 2). The circuit board includes a wireless module for transmitting and receiving data. The module is away from the infant to ease parents’ concern of electromagnetic waves from the wireless module. A drastic variation of CO 2 concentration will produce an abrupt change in sensor outputs and the processor will be activated to send out an alarm signal. With the RFID approach, an identification (ID) signal of the infant will be sent out to correlate the sensing/alarm signals with the ID. This will significantly reduce the labor costs and time. The sensor data 2007 IEEE International Conference on RFID Gaylord Texan Resort, Grapevine, TX, USA March 26-28, 2007 WeAT1.2 1-4244-1013-4/07/$25.00 ©2007 IEEE. 134