Sensors and Instrumentation to Meet Clinical Needs

Abstract

There are many challenges that still plague the development of biomedical sensors and instruments. These range from basic science through the practical application and clinical evaluation of developed devices. In this presentation we shall examine some of the special applications of sensors and instrumentation to address clinical problems. In too many cases technology is developed without a specific application, and that has to come later if at all. A different approach is to start with the clinical problem and develop technology that can address it. An example of this is work done more than 30 years ago, but it illustrates how technology can address a clinical problem. In the early days of neonatal monitoring miniaturized versions of adult electrodes were used to pick up cardiac and respiratory signals from an infant. These electrodes and their method of attachment caused irritation to the infant’s skin and also would create significant shadows when they were left in place as x-ray images were obtained. Both of these problems were overcome by the development of thin-film flexible electrodes. Another issue was related to the reliability of infant breathing and apnea sensors. A clinical study showed that the dominant technology for sensing breathing, transthoracic electrical impedance, was not very reliable when the infant was moving. In a study of 34 infants each studied for four hours, breathing signals could only be detected 43% of the time using transthoracic impedance during movement. On the other hand, fast-responding nasal temperature sensors and compliant strain gauges recorded simultaneously with the transthoracic impedance data were shown to give more reliable data at 79 and 50 percent of the time respectively. Thin-film sensors have been developed that use these more reliable methods of sensing infant breathing. Such sensors in themselves do not fully address the problem, for it is a clinical problem, and basic questions such as is what is being sensed and is it an appropriate way to deal with the disease process. In the case of infant apnea monitoring, it was found that in many cases apnea monitoring alone would not affect the basic clinical problem. Thus, while developing sensors and instrumentation is important, one must not lose sight of the clinical problem, and part of the development activities should go into clinical studies justifying the instrumentation in addressing the disease. The Collaborative Home Infant Monitor Evaluation (CHIME Study) was a major clinical study undertaken by the U. S. National Institutes of Health (NIH) to determine the utility of home infant apnea monitoring. The results of this study demonstrated that infants were experiencing life-threatening episodes at times other than when apnea was occurring. Thus, such a study helped to put the technology in an appropriate clinical perspective. Other examples of sensors and instruments that address important clinical problems will be presented.