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Wireless Technologies Find Niche in Patient Care

Medical Device & Diagnostic Industry

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An MD&DI August 1998 Column

Wireless and remote-access technologies facilitate patient data gathering in hospitals and home-healthcare environments.

Changes are taking place in the way medical data are gathered and transmitted. New technologies from the computer and communications industries are being tailored into wireless systems that promise to make healthcare more effective and efficient.

Most of the progress has been made on the receiving end. Palmtop PCs, pagers, and even cellular telephones have been adapted to receive radio transmissions and display patient data. But this is only the beginning.

Before the end of this year, one or more wireless patient monitors—custom-made for medical use—are expected to enter the U.S. marketplace. Industry sources say they will draw their data from lightweight sensors designed to maintain patient mobility. The sensors, possibly attached to patient arms, will read vital signs and convey the data to a wireless transmitter.

Data Critical's MobileView system (open, left, and closed, right) allows physicians to receive ECG waveforms remotely, off-site.

These emerging technologies will join a growing number of conventional patient monitors that have been enhanced with transmitters and receivers that allow wireless links to hospital information systems. Like the current generation, the new monitors will work within the framework of existing networks. Some will use special nodes connected to the conventional hardwired networks—the Ethernet or Token Ring systems—that serve as the information backbones of hospitals and clinics across the United States. Others will use encryption and compression technologies to transmit medical data over cellular telephone networks, which then pipe the data by modem into the hardwired networks.

The hallmarks of these wireless-ready systems are easy to recognize. Antennas, screwed into the walls at the ends of corridors, receive signals fired off by sensors and their associated telemetry units, and pass the data into the hardwired network. Alternatively, some antennas provide the means for accessing the network, so data can be drawn from the central system.

Transmission rates vary, but the result is generally satisfactory, according to Charles Becker, president of Technical Concepts Corp. (San Antonio, TX), a network integrator known for combining modes of data transfer within clinical settings. "The data rates are pretty high," Becker says. "You can take a notebook computer or a specialized handheld and walk around a ward looking up patient data and graphs. I really see the portable handheld devices being a fast-growing segment."

Wireless devices are popular because they facilitate the flow of information. Nurses no longer need to go back to a central location to check the latest doctors' orders. Physicians making rounds can call up the patient's complete history and know it is as up-to-date as possible. Moreover, if the nodes for monitors are wireless, equipment can be easily moved around the hospital.

"The whole key to wireless is flexibility," says Karyn Beckley, vice president of corporate administrative services at Spacelabs (Redmond, WA). All Spacelabs monitors, she notes, are equipped for wireless operation. They can be easily moved from place to place and patient to patient. "That allows monitors to be placed without hardwired connections so hospitals can more easily reconfigure their resources," she says.


This flexibility is not achieved without a price. The bandwidth on a wireless channel is smaller than on a hardwired channel, which means data move more slowly over the wireless portion. The developers of wireless medical products have been trying to counter this limitation by boosting the efficiency of their products.

"Everybody in this industry is trying to improve performance so that the user doesn't see any difference between the wireless and hardwired portions of the network," says Dan Wilson, Spacelabs' product development director. "In our own systems, we've seen a 400% throughput increase in the last two years, and we are continuing to work on it."

Data Critical Corp. (Redmond, WA) has adapted wireless technology initially designed for general consumers to create several products for medical applications. Its goal is to improve communications by offering a variety of monitors with different levels of functionality. All of its products address the same issue, says Brad Harlow, vice president and general manager of Data Critical.

"The role of wireless is to connect the caregiver directly to the information in real or near real time," Harlow says. "It is to provide the nurse or the doctor with the information necessary to be able to make a patient decision quickly."

Two of Data Critical's products stand out—StatView and MobileView. StatView, which cleared FDA on April 13, is built around a handheld wireless receiver 20 mm thick and about the size of a credit card. It is also marketed under the trade name by Marquette Medical Systems (Milwaukee) and provides patient alarm data from the bedside and telemetry monitoring networks. Using a three-button interface, users can scroll through a list of critical patient information, such as name, bed number, alarm condition, and heart rate. Within 10 seconds of an alarm, the handheld device displays the patient's 6-second pre-event and current ECG waveforms. The device is compatible with hospital networks, including those offered by Marquette and Hewlett-Packard (Palo Alto, CA). Encryption and compression algorithms ensure confidentiality, speed, and accuracy.

MobileView, which cleared FDA on February 16, is essentially a wireless Nokia 9000i telephone that receives transmitted vital signs. Several types of information can be accessed, including telemetry, monitored waveforms, and 12-lead ECGs. When coupled with Data Critical's technology, the server transmits information from patient-monitoring systems to the screen of the Nokia 9000i. Not only does the physician have access to this information on demand, but the Nokia system offers speakerphone and Internet access and the ability to send faxes and E-mail.

The Nokia system's visual resolution is on a par with hospital patient monitors, Data Critical says. Users can store on-line information for later review. A high level of encryption along with compression technologies help ensure patient confidentiality and accuracy.


There are similarities between telemetry and wireless monitoring, but ultimately the two are very different. For example, a handheld telemetry system from Hewlett-Packard, the Viridia Wave Viewer, displays integrated ECG and oxygen saturation information on a palmtop PC. The Wave Viewer allows practitioners to review vital signs instantly at the patient's bedside. Although the system does what wireless vital signs monitors are supposed to do, it does not connect to the central information system. Rather, it taps into the telemetry transmitter using an infrared link or a fiber-optic light pipe. As a result, telemetry systems are limited in terms of the data they can access. Wireless patient monitoring, on the other hand, supports a virtually unlimited scope of data.

At the touch of a button, the handheld screen of a wireless system can display anything recorded about the patient. The patient's medical record is available for perusal, as is the patient's financial and administrative data. Wireless access points strategically located throughout the facility serve as bridges to the hardwired information networks.

"These are small boxes that fit on the wired network and basically provide the interface between the mobile client device and the server or other computing resource that is on the wired LAN," says Lynn Chroust, product marketing manager at Proxim, Inc. (Mountain View, CA), a supplier of local area network (LAN) technology.

The mobility and flexibility of wireless technologies make them ideally suited for assisting in emergency situations, but wireless devices can also address economic and quality-of-care concerns. "With reduced staffing levels, many hospitals are looking closely at monitoring systems that improve efficiency and enhance flexibility," says Carl A. Lombardi, CEO of Spacelabs. "We believe (wireless) networking will help clinicians provide the best possible patient care in a number of situations.

Spacelabs has been a strong advocate for wireless technology. In early 1997, the company unveiled its Wireless Ethernet, a patient-monitoring network that integrates wireless and hardwired monitors with ambulatory patient telemetry transmitters. Using this technology, hospitals can network wireless portable monitors, hardwired bedside monitors, and telemetry transmitters into one central station monitor. The Wireless Ethernet network could also provide interactive bed-to-bed communications between wireless and hardwired monitors. Patient information coming from the wireless monitoring is integrated with hardwired clinical information systems and hospital information systems.

In addition to the Wireless Ethernet network, the company offers its wireless PC Ranger monitor, portable PC Scout and PC Express monitors, and multifunctional Universal Clinical Workstation and PC monitor. The PC Ranger and Scout display vital signs, including 12-lead ECG with ST segment (which can indicate cellular injury), arrhythmia, temperature, respiration, blood pressure, pulse oximetry, and EEG. The monitors have a touch screen user interface that speeds access to information. Information on the hybrid hardwired and wireless network can be remotely accessed via computer and modem by tapping into Spacelabs' PCIS Physician Workstation system.

In January, Spacelabs expanded its wireless capability with the SL1050 portable monitor, designed for monitoring acute myocardial infarction patients being transported from the emergency department to the cath lab or critical-care unit. The SL1050 offers, in a portable form, the large display and advanced processing found in conventional bedside monitors. Its power management system increases transportability, and its modular design ensures that critical information, such as arrhythmia and ST segment deviation, will not be interrupted if the monitor travels out of the central antenna range. The SL1050 can be used in combination with other Spacelabs' monitors, both wireless and hardwired. It includes a 10.4-in. active-matrix LCD screen, five-trace-color touch screen display, and bedside-based arrhythmia and ST segment analysis.


One of the most useful potential contributions of wireless is to permit the electronic medical record (EMR) to augment or even replace paper-based records. Wireless technology promises to allow healthcare practitioners to call up patient data instantly at any bedside.

Physix (Houston) offers two EMR products, PocketCHART and Compendia, software packages that include patient-charting tools coupled with supporting systems and reference materials. In addition, the software offers the appropriate wording and structure to substantiate data for submission to Medicare by solo practitioners (PocketCHART) and members of a group practice (Compendia). The software also supports a detailed description of the patient visit. The template system can be captioned to grab patient data gathering, recording data in a manner consistent with Medicare guidelines.

Both Compendia EMR and PocketCHART work with a variety of palmtop PCs, including Cassiopeia PA-2400 by Casio, which provides preinstalled voice and handwriting recognition. The writing tablet eliminates the hardware keyboard, allowing quick access to information on the screen. The two software products also work with Compaq's PC Companion.

These mobile computing platforms, which are small enough to be routinely carried by practitioners, run on the Windows CE operating system. "Development of the wireless technology for the Windows CE platform is a critical element in meeting real-world needs in health care," says Steve Spar, vice president of engineering at Physix. Windows CE gives users a standard operating system on which they can easily and reliably move data.

Nowhere is this kind of reliability more critical than in the network itself—and for that reason, certain basic technologies have become de facto standards. One is the frequency at which wireless data are transmitted.

Wireless networks have gravitated toward an operating radio frequency of 2.4 GHz to reduce susceptibility to interference from other electronic devices. Early networks operated between 902 and 928 MHz, frequencies crowded with applications such as cellular and cordless phones and pagers. Data transmission speeds are generally at or above 1.6 Mb per second.

Other staples of wireless networks include antennas with a range of about 500 ft in closed areas or 1000 ft in open ones and chip sets or modules that transmit and receive these signals. These allow users to roam the halls and rooms of the hospital or clinic and remain tied into the network, using access points as bridges between the wireless devices and the wired LAN.

Most wireless technology can be used interchangeably in different environments. Antennas, however, need some tweaking to work well in particular areas. Some antennas look like wands, others like flat squares.

"Hospitals tend to be in T shapes, so we've come up with a variety of antennae that help us maximize the coverage we can get without installing a lot of access points," says Chroust.

Proxim has focused on healthcare and claims to have 95% of the market segment for wireless technologies. Much of that turf was gained only recently.

The breakthrough for Proxim—with a 2.4-GHz wireless LAN—came in 1994. Today, its frequency-hopping, spread-spectrum wireless technology consists of PC card wireless LAN adapters and interchangeable antennas, as well as access and extension points that serve as wireless bridges to hardwired networks, including Ethernet and Token Ring.

Versions of the company's RangeLAN operate at either 1.6 or 2 Mb/sec per channel. Up to 15 independent wireless LANs can operate in the same physical space, providing roughly 24 Mb/sec of total network bandwidth. The LANs support Windows CE 2.0, which clears the way for the use of handheld devices such as the Hewlett-Packard HP 620 LX palmtop PC. Proxim technology is also compatible with the Fujitsu TeamPad 7600 pen-based portable computer, which provides mobile access to the patient's medical records on full-sized VGA screens instead of the palm-sized screens of other handheld devices. The trade-off in weight is minimal; the TeamPad 7600 weighs 1.7 lb.

The cornerstone of the RangeLAN is a module embedded into handheld PCs and bedside terminals. This module is about two-thirds the size of a business card and weighs less than an ounce. In concert with Proxim's LAN technology, this module helps conserve battery power.

"Power consumption is one of the devils of a wireless LAN device," says Chroust. "You won't be able to get the utility out of a device that is too highly power consumptive, because you'll always be changing batteries. We have, over the years, driven down power consumption to allow the kind of eight-hour mobility that nurses and doctors need, and that's why you see such widespread usage of our products in the healthcare environment."


Proxim has made a number of key alliances in the medical community. Physix uses Proxim technology for its EMR products, as does Cerner Corp. (Kansas City, MO). "Mobile computing devices and radio-frequency networks are key to bringing computing power to the point of care," says William G. Waters, managing director at Cerner.

Specifically, Cerner uses RangeLAN technology with its Health Network Architecture (HNA) Millennium, a fifth generation of HNA designed to manage and automate the health-care process. HNA Millennium uses object-oriented client/server software that runs on open industry-standard platforms and features a relational database. At the core of its architecture is a lifetime EMR tied to decision support software and integrated with systemwide messaging capabilities.

Proxim has also allied with Shared Medical Systems Corp. (Malvern, PA), which markets and supports Proxim's LAN technology as part of its clinical, financial, and management information systems. The alliance opens the door to a vast expansion of Proxim technology because Shared Medical serves more than 3500 customers in 20 countries.

Another ally, Medic Computer Systems (Raleigh, NC), uses RangeLAN wireless technology to extend its clinical information systems to mobile physicians. Medic software automates financial, administrative, managed-care, and clinical information functions for individual physicians and managed-care organizations. LXE, Inc. (Norcross, GA), a technology partner with Proxim, provides radio-frequency integration, installation, and maintenance services for Medic's wireless computing products. Currently, Medic supports more than 9000 medical practices representing more than 38,000 physicians in 49 states.

Health+Cast (Horsham, PA) is also working with Proxim, providing Galileo software to link wireless technologies to legacy servers sharing clinical information. With Galileo, users without software programming skills can modify screens. This graphical makeover may include adding bit maps, buttons, drop-down boxes, pick lists, and navigation bars to existing screen sets. Additionally, intelligent objects can be dropped into the application to enhance the functionality of the legacy system. Internet links and tasks such as scheduling document management can be added. Galileo also provides a critical link to Web-based clinical information by using Microsoft Pocket Explorer on its Windows CE–compatible handheld device.

Although Proxim may hold a commanding share, other suppliers have a strong hook in the market. Aironet Wireless Communications, Inc. (Fairlawn, OH), is one of these. Like Proxim, Aironet uses advanced spread-spectrum radio technology as the cornerstone of its wireless LANs. Since 1992, the company has shipped more than 300,000 spread-spectrum wireless devices. Most are used outside health care, but at least some have entered the health-care market connected to the Marquette Unity Ethernet system as part of an alliance between Aironet and Marquette Medical.

Marquette executives view wireless technology as an ideal means for keeping track of patients en route from one place to another.

"For ER patients, when they are going to and from diagnostic tests is one application. Another is for when patients are being transferred to another unit or moved out of ICU for special procedures," says John Pendergast, product manager for wireless LAN at Marquette Medical Systems. "Wireless is a way to continue to monitor them from a central station while they are being moved."


Today's expansion of wireless technology is made possible partly by the establishment of standards. The IEEE 802.11 standard, a wireless LAN specification first conceived in 1990, sets guidelines for the interface between a wireless device and a base station or access point, and for devices that are hardwired together. IEC 601-1-2, the European safety specification for radio-frequency (RF) devices in health care, has been implemented in a number of areas considered sensitive to RF interference, such as neonatal monitoring and intensive care units.

Many devices also comply with the OpenAir wireless LAN standard set by the Wireless LAN Interoperability Forum (WLIF), a nonprofit organization of more than 25 leading wireless vendors that supports interoperability among members' products.

Choosing between standards depends as much on the requirements of the application as the preference of the company and customers. Adhering to the IEEE 802.11 standard allows faster data transmission, but at the cost of increased power consumption.

"We can't use it for the Windows CE device—and this [Windows CE] is one of the things gaining popularity in health care," says Chroust.

Marquette Medical, on the other hand, chose to be 802.11 compliant. "It's important to know the standards because there are a lot of wireless devices that are not compliant or compatible and won't be able to work on the same network," says Pendergast.

Testing products against certain standards verifies that the products comply and that they will work with each other under certain circumstances, a relief for anyone who has ever tried to network incompatible products. Similar peace of mind may come from SWAP (shared wireless access protocol), an evolving common interface specification to support wireless voice and data services in the home.

Just as wireless monitors in the hospital provide a link to hospital- or clinic-based information systems, so might wireless devices in the home periodically call up and download data into these information systems. "The technology exists today for both the wireless LAN side and to do remote dial-up access," says Chroust. "I just think it is more a matter of time than anything for a company to put together a successful total solution and start bringing it to the home-health-care markets."


Home-based units that are already on the market hint at such a future. Using a standard telephone connection, Sabratek Corp. (Niles, IL) has devised several home-healthcare products that allow practitioners to monitor home-bound patients, adjust their therapies, and evaluate outcomes. This extension of technologies is part of Sabratek's Virtual Hospital Room concept. Key to the concept is MediVIEW, software that allows remote programming and monitoring of the company's IV infusion pump use. This pump dispenses any of several solutions, including parenteral nutrition, antibiotics, chemotherapy, and pain medication. Together with MediVIEW, the system facilitates patient management.

"The provider can download an entire data log on the patient," says Stephen Axel, vice president of marketing for Sabratek. "While patients may assume they completed the therapy, their pumps' data logs may show differently. In essence, we have a new tool to remotely measure and ensure compliance."

The real advantage of remote access technologies is allowing patients to leave the hospital sooner. Faint indications of the ultimate economic and quality-of-life benefits from home-based applications are already appearing. For example, one anecdote tells of an elderly patient, admitted repeatedly to the hospital for ischemic cardiomyopathy, who broke free of the hospitalization cycle by using a remote monitoring and tracking system. The system spared her from entering the hospital at all in 1997, according to her doctors. She otherwise could have been expected to spend 20 to 30 days under institutional care. Savings, calculated by figuring charges for a medical/surgical bed minus 50 home-care nursing visits, came to approximately $21,000 for that year alone.


Wireless technologies may bring significant changes in patient handling—and none too soon. The cost of labor is rising at precisely the time when a premium is being placed on cost control. Healthcare practitioners, therefore, must be more productive while maintaining or improving the quality of care. Wireless technologies may be among the tools needed to meet this challenge.

Copyright ©1998 Medical Device & Diagnostic Industry

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