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National Academy of Engineering (US) and Institute of Medicine (US) Committee on Engineering and the Health Care System; Reid PP, Compton WD, Grossman JH, et al., editors. Building a Better Delivery System: A New Engineering/Health Care Partnership. Washington (DC): National Academies Press (US); 2005.

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Building a Better Delivery System: A New Engineering/Health Care Partnership.

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Wireless Biomonitoring for Health Care

Thomas F. Budinger

Lawrence Berkeley National Laboratory and University of California, Berkeley

Biomonitoring methods have developed substantially since 1965, and wireless technologies of the last few years promise major advances in efficiency by simplifying hospital and home health care. Improved technology has led to better sensors for monitoring pulse, heartbeat (ECG), blood pressure, blood oxygenation, physical activity, falls, vascular compliance, and even endoscopy. But what about communication between the patient and caregiver and between the patient and the environment (e.g., brain-computer interfaces)? If we could do anything we wanted with wireless technology for health care, what would we choose? This analysis argues for inexpensive engineering technologies that improve health care and substantially improve the quality of life for patients who are severely disabled from spinal cord injury or aging processes.


A few commercial medical-alert networks provide communication between the subject and a remote communication center, similar to contemporary fire and burglar alarm systems. These systems are designed to be used by a conscious subject to alert loved ones or caregivers in case of a fall, trauma, or cardiac arrest. Of some 300,000 falls a year in the United States, 10 percent happen to people at home alone who are not discovered for more than an hour after the fall. One-third of people over 65 who fall and are not found for more than an hour are seriously disabled or die (Gurley et al., 1996). This is a very serious problem.

Current devices for monitoring falls have some serious flaws, and innovations are urgently needed. Commercial devices are costly, bulky, and not scalable to contemporary communications. They rely on a type of fire-alarm system that is commercially operated at a monthly cost of $20 and depends on an answering operator putting the subject in contact with the appropriate response team or person. Indeed, a variety of monitors currently on the market have limited range and a layered communication system that is not flexible enough to meet the needs of patients and loved ones at home alone. We need wearable systems that can communicate through a local low-power communications system to a module that then connects to the Internet, land lines, or specified cell phone numbers.

There are more than 400,000 cases of sudden cardiac death (SCD) each year. The key element in resuscitation is the time interval between the cardiac event and the administration of professional aid. We need a reliable communication interface to a patient-friendly device that can detect falls or irregular heart action (e.g., a wrist-worn device that monitors pulse or a chest-strap device that monitors electrical events) to ensure against SCD, particularly when the patient is sleeping.

Commercial tracking devices also need improvement. Commercial systems advertised for tracking elderly patients with Alzheimer's disease are available, but they are expensive and not scalable at low cost to a wide variety of situations. It is possible, using GPS with a combination of modern communication networks (e.g., 802.11, ultra-wideband) to create a wireless system that monitors not only location but also the health status of individuals, just as we monitor the location and status of automobiles. In fact, there is no barrier to engineering customized tracking systems that can locate a wandering family member or a lost pet and, in addition, provide information on some physical signs, such as activity, pulse, temperature, and so on.


A commercial system that can track people or pets over a distance of 1.5 miles from a base station has been developed by Wheels of Zeus Inc. (WoZ). The system operates at about 900 Mhz and uses small poker-chip-like tags attached to the subject. Each tag has a GPS and local wireless device and an option for storing data related to the subject. The system requires a base station (a few base stations could serve an entire town). In field trials in February 2005 (evaluated by me), the system proved to be highly reliable in most terrains. A commercial version should be available in late 2005 (WoZ, 2005).


Patient-centered home telecare and health systems have shown great promise, but little modern engineering is being used to develop them. Wellness promotion now focuses on bringing patients home and caring for them at home, a very practical idea. Improved monitoring systems could greatly facilitate the objective of caring for patients at home.

A study has been going on in Australia for the last few years to monitor the physiological condition of patients at home (Wilson et al., 2000). This study is of great interest to the National Cancer Institute, which is looking for a way to monitor the drug therapy of cancer patients in a home setting. Participants in the study wear a radio connected to a number of sensors, including a blood-pressure monitor. The information is sent through a modem to a central location. The results of this and other studies on child monitoring (Neuman et al., 2001) have shown that remote sensing is reliable and can replace home visits. However, wireless communication methods are still not standardized.

Wireless technology that can transmit images of patients, as well as monitor vital signs, via radio or TV frequencies has existed since 1965. Years ago when home monitoring was first considered, the available technologies were encumbered by FCC regulations. In 2005, however, wireless technologies can reach almost anywhere on the planet via the Internet, cell phones, or other hand-held devices, and WEBCAM technology can visualize patients and health care monitors or situations. Many physicians would agree that the number-one priority for patient in-home care is ready access to a video of the patient or the patient's bedside monitor. At this point, however, although the technology exists (e.g., WEBCAM), it is not adaptable to a scalable system. Improving video monitoring of home-care patients will require the participation of engineers, physicians, and nursing support institutions.


A recent example illustrates the need for wireless monitoring in a hospital. In February 2003, 60 percent of the patients admitted to Children's Hospital in Oakland, California, a major hospital in the Bay Area, were admitted for infections with respiratory syncytial virus. Treatment for this condition is mainly by oxygen delivery, and oxygenation is monitored by pulse oximetry. Patients being monitored must wear a wire connected to a bedside unit from a toe or finger. Figure 1 shows the chaotic scene on the wards using this wired system.

FIGURE 1. A wired system to monitor oxygenation by pulse oximetry.


A wired system to monitor oxygenation by pulse oximetry.

With a wireless system, false alarms due to motions of wires and disconnects would be eliminated (Figure 2). In addition, hospital stays could be shortened from four days to one and one-half days with reliable respiratory monitors and pulse oximeters with oxygen controls appropriate for home care. The engineering agenda for creating the monitoring device is a lightweight, reliable power supply for the pulse oximeter and wireless transmitter.

FIGURE 2. A wireless system for monitoring oxygenation by pulse oximetry.


A wireless system for monitoring oxygenation by pulse oximetry.

My group has built a small pulse oximeter that can be worn on the forehead and that uses the Bluetooth or another system (802.11, 802.15 “mote”) for local wireless transmission. Pulse oximeters already on the market could be used if they were adapted for wireless transmission (e.g., the Minolta Pulsox™ system that can be worn on the hand and costs about $240) (Figure 3). The device would communicate with a modem or router situated within 10 meters of the subject through which the data would be uploaded to the Internet where it would be available to caregivers.

FIGURE 3. A Minolta Pulsox™ system.


A Minolta Pulsox™ system.

Sleep apnea is a serious health problem related to cardiovascular disease. Yet, for many people with sleep apnea, the only monitor is a sleeping partner. The gadgets now sold to monitor episodes of sleep apnea are bulky, expensive, and complicated. If they were re-engineered to be wireless, they would be much simpler and smaller (Figure 4).

FIGURE 4. Wired (left) and wireless (right) systems for monitoring sleep apnea.


Wired (left) and wireless (right) systems for monitoring sleep apnea.

Another wireless device is a breathing sensor incorporated into a strap around the chest similar to the device used to monitor pulse in athletes. Wireless transmission to a local receiver can facilitate recording, alarms, and further transmission to data archives.

One of the newest ideas for wireless monitoring is to use ultra-wideband frequency technology. For example, one could use a crib-installed radar device to monitor a baby's breathing. An electronic signal-processing system would set off an alarm if lung motion were abnormal or absent (Budinger, 2003).


Accelerometers used to evaluate how much activity an individual expends during a day could be used to monitor the activity of patients at home. Current accelerometers (produced by four different companies) are all one dimensional. A three-dimensional accelerometer could potentially pick up both the activities and pulse rate of a patient who has fallen or who is lying down. The same system could also detect a fall reliably with a low rate of false alarms. A reset button could be pushed in case the fall alarm was triggered accidentally. In addition, 3-D accelerometers the size of a nickel could improve GPS tracking systems.


High blood pressure is one of the major risk factors for heart attacks and heart failure. But of the 50 million people in North America with high blood pressure, 30 percent do not know that their pressure is abnormally high and that they would benefit from medical treatment (Mensah, 2002). A single blood pressure measurement during a visit to a doctor's office or clinic is extremely unreliable. A simple, inexpensive ($75) blood pressure monitor that can be worn on the wrist was manufactured in 2003 by Omron, and based on tests by the author, the device is reliable. Other devices available in 2005 are 60 percent less expensive, but their reliability has not been verified.

However, a wireless device must await the establishment of a practical communication network for convenient transmission to caregivers. Such a system could be combined with the WoZ network, or a router could send transmissions from the blood pressure or other monitoring device to the Internet.

Another monitor for measuring compliance of the vascular system could possibly be developed within five years. Ideally, this would be a simple wrist-worn device that transmits the arrival of a pulse and a chest strap that transmits the time of the R wave (Figure 5). The time difference between these measurements is proportional to the compliance of the vascular system and reflects endothelial function. This device would require a wireless timing signal between the heart electrical event and the pulse arrival at the wrist. The system could take repeated measurements to demonstrate vascular response to psychological stress and changes associated with drugs and foodstuffs. This wireless unit could also transmit information to a permanent record or to a caregiver (Budinger, 2003).

FIGURE 5. Wireless system for measuring vascular system compliance.


Wireless system for measuring vascular system compliance.

Another device now under investigation is a wireless colonoscopy that can monitor for signs of colon cancer. The subject swallows a little disposable transmitter that takes pictures as it travels through the colon and transmits them to a recorder worn on a belt (Appleyard et al., 2001). A problem with this device is that a clinician has to look through all of the pictures.


The incidence of spinal cord injuries in the United States is 11,000 cases per year, and there are currently about 250,000 patients. The annual medical cost of caring for these patients is $9.3 billion (NSCISC, 2004). The cost could be substantially reduced and the quality of life for these patients improved by new techniques of wireless communication. Electronic equipment and wireless communications can make it easier for quadriplegic patients to control powered wheelchairs, light switches, heating devices, televisions, radios, telephones, and computer systems for learning, entertainment, and communications (Friehs et al., 2004; Keirn and Aunon, 1990).

An array of small electrodes implanted into the brain of a 25-year-old quadriplegic man was programmed through wired connection signals to control a computer cursor (Figure 6A). After a short learning period, the patient was able to check his e-mail and control aspects of his environment by moving a cursor on a computer screen with his thoughts alone. The system, called BrainGate™, is an investigational device being tested clinically by Cyberkinetics Inc. (2005). At this point, Brain Gate is not an approved device and is available only through a clinical study. The innovations are the implanted electrode system and the module that interprets brain signals and translates them into control of devices. The system could potentially be used to help people with disabilities become more independent by allowing them to control various devices with their thoughts.

FIGURE 6. Brain-computer interfacing.


Brain-computer interfacing. A. Implanted electrodes. B. External electrodes. C. Tongue-operated intra-oral remote controller.

Monkeys with similarly implanted electrodes have shown that brain signals can move robotic arms in two dimensions (Taylor et al., 2002). More recently, an array of external electrodes have been used as a brain-computer interface that can translate externally detected brain signals (Figure 6B) into both horizontal and vertical movements of a computer cursor (Wolpaw and McFarland, 2004).

Another approach that does not require invasive electrode implantation or an array of electrodes on the surface of the scalp is to use the tongue to control a cursor, just as one would use a touch pad or a mouse. The idea of using an intraoral device with tongue switching dates back to 1990 (Parker and White, 1990), but a fully wireless implementation has not yet been developed.

Nevertheless, this idea has many practical advantages over other systems that have been proposed for quadriplegic patients (Figure 6C). The tongue-operated intra-oral remote controller consists of an acrylic plate fitted to the roof of the mouth. A capacitor-based platform on the plate is similar to the touch pad of a laptop. The electronics of the pad are in resonance with a loop antenna around the head or neck that senses the tongue activations by a power drop. This information can then be sent wirelessly to a computer or other pick-up device to control light switches, a television, and even movement of a wheel chair.

The device could also be used to send messages by tongue taps for transmitting Morse code (Yang et al., 2003). Alternatively, the intra-oral wireless signaling device could be used in conjunction with a head-mounted pointing system that employs a laser or infrared beam (Chen et al., 1999).

Another method is to use an infrared-controlled human-computer interface with a laser pointer and infrared-transmitting diode mounted on the patient's eyeglasses. Using the laser, the patient could point to a computer cursor control panel and keyboard equipped with an infrared receiver. With his or her tongue, the patient would key a switch on the side of the cheek suspended from an arm also mounted on the eyeglasses. When the laser points to the desired target on the computer control board, the patient would key a switch “to send” the infrared signal (Chen et al., 1999).


Many wireless systems operate with low power at 2.45 gigahertz; thus, they have very short range (e.g., 10 meters or less). Even though these systems are not regulated by the FCC, their use in hospitals has been limited. The purpose of the prohibition against using cell phones in hospital environments is not only to prevent voice interference out of respect for patients, but also, in some cases, to prevent interference by high-power wireless transmissions with devices used in acute care, such as monitors and infusion systems. This problem now seems to be coming under control, and wireless systems are being widely used in hospitals across the country.

In February 2003, the FCC finally endorsed a new ruling loosening restrictions on unlicensed ultra-wideband radio transmissions. In principle, this technology enables one to see through walls, monitor patients, and implement communications in radiofrequency-busy environments without interference, thus opening enormous possibilities for wireless transmissions in hospitals and in homes with devices that do not interfere with each other. Thus, the limitations of wireless communications for medical sensor devices have disappeared, and opportunities for improving health care abound.


This paper was prepared with the assistance of Kathleen Brennan, Jonathan Maltz, Thomas Ng, and Dustin Li. The work was supported by the U.S. Department of Energy Office of Biology and Engineering Research.


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Copyright © 2005, National Academy of Sciences.
Bookshelf ID: NBK22846


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