Wearable sensors/systems and their impact on biomedical engineering

ecent advances in miniature devices, as well as mobile and ubiquitous computing, have fostered a dramatic growth of interest for wearable technology. Wearable sensors and systems have evolved to the point that they can be considered ready for clinical application. This is due not only to the tremendous increase in research efforts devoted to this area in the past few years but also to the large number of companies that have recently started investing aggressively in the development of wearable products for clinical applications. Stable trends showing a growth in the use of this technology suggest that soon wearable systems will be part of routine clinical evaluations. The interest for wearable systems originates from the need for monitoring patients over extensive periods of time. This case arises when physicians want to monitor individuals whose chronic condition includes risk of sudden acute events or individuals for whom interventions need to be assessed in the home and outdoor environment. If observations over one or two days are satisfactory, ambulatory systems can be utilized to gather physiological data. An obvious example is the use of ambulatory systems for ECG monitoring, which has been part of the routine evaluation of cardiovascular patients for almost three decades. However, ambulatory systems are not suitable when monitoring has to be accomplished over periods of several weeks or months, as is desirable in a number of clinical applications. Wearable systems are totally nonobtrusive devices that allow physicians to overcome the limitations of ambulatory technology and provide a response to the need for monitoring individuals over weeks or even months. They typically rely on wireless, miniature sensors enclosed in patches or bandages, or in items that can be worn, such as a ring or a shirt. They take advantage of hand-held units to temporarily store physiological data and then periodically upload that data to a database server via a wireless LAN or a cradle that allow Internet connection. The data sets recorded using these systems are then processed to detect events predictive of possible worsening of the patient’s clinical situation or they are explored to assess the impact of clinical interventions. All these aspects of wearable technology are covered by this special issue, which is introduced by four commentaries of physicians who share with the readership their vision on future clinical applications of wearable technology, thus pointing out its tremendous potential. Phil Binkley, M.D., professor of medicine at The Ohio State University Division of Cardiology, shares with us his vision on potential applications of wearable devices in cardiovascular research and clinical practice. Walter Frontera, M.D., Ph.D., chairman of the Department of Physical Medicine and Rehabilitation at Harvard Medical School, provides us with a clinician’s viewpoint of the dramatic improvements in patient management that wearable devices could foster. David G. Standaert, M.D., Ph.D., associate professor of neurology, Harvard Medical School and associate neurologist at Massachusetts General Hospital, points out in his commentary the clinical relevance and potential outcomes of monitoring motor fluctuations in patients with Parkinson’s disease. Finally, Joel Stein, M.D., director of the stroke program and chief medical officer at Spaulding Rehabilitation Hospital, highlights the need for monitoring poststroke hemiplegic patients in the home and outdoor environment in order to assess the impact of clinical interventions and plan more effective rehabilitation strategies. The first five articles of this special issue are focused on the development of sensors and systems. In the first article, Asada et al. describe the evolution of the ring sensor over the past eight years. This is likely the most renowned project in the area of wearable devices. The result of several years of work is a pulse oximetry sensor that allows one to continuously monitor heart rate and oxygen saturation in a totally unobtrusive way. The device is shaped like a ring and thus it can be worn for long periods of time without any discomfort to the subject. The ring sensor is equipped with a low-power transceiver that accomplishes bidirectional communication with a base station, thus allowing one to reconfigure the sensor when necessary and to upload data at any point in time. In a nutshell, this is a “jewel” in the wearable technology arena. The second article, by Park and Jayaraman, demonstrates the great impact on the clinical potential of wearable systems of the Georgia Tech Wearable Motherboard, the result of a revolutionary idea that allowed Dr. Jayaraman’s team to develop a garment (i.e., a shirt) that actually functions as a wearable health monitoring system. This concept has been developed into a product that is now commercially available and allows one to record heart rate, body temperature, motion, position, barrier penetration, and the like in a totally nonencumbering manner. Park and Jayaraman point out a