Patient monitoring in the fast lane: New York emergency department uses a virtual local area network within their existing AP network to continuously monitor patient vital signs, while running other applications on the same network

Timothy Rhue

At Samaritan Medical Center (SMC) in Watertown, N.Y., we needed to continuously monitor patients' vital signs as we moved them from the emergency department (ED) to radiology. To maintain the monitoring signals, we planned to implement wireless technology, but we had to balance competing data demands across a finite bandwidth within our hospital. Several years of research and development led us to achieve a Wi-Fi solution that prioritizes critical monitoring data from the ED while continuing to service other departments in the hospital.

Traditionally, patient monitoring has required its own separate, dedicated network to guarantee security and performance. Now, using a virtual local area network (VLAN) within our existing network, we can put critical patient monitoring data in the "fast lane," ahead of administrative applications.

From Wired to Wireless

SMC is a 287-bed community medical center that serves as a regional referral center for northern New York. With more than 9,100 admissions annually and 37,500 emergency visits last year, SMC is the largest provider of healthcare services between Burlington, Vt., and Syracuse, N.Y. Our 1,600 employees make us the largest private employer north of Syracuse.

In 1999, we purchased a wired monitoring system for the ED from a business unit of Siemens Medical Solutions that later became part of Drager Medical of Telford, Pa. However, our long-term plan was to improve upon our previous wireless monitoring system and replace the wired system with wireless. Our previous wireless system had used radio frequency (RF) transmission, and although the antennae were correctly positioned throughout the ED and radiology, the lead walls in the diagnostic area caused complete loss of signal when moving patients into radiology rooms for X-rays and scans. The signal was also subject to cellular phone and electrical equipment interference problems.

When Drager Medical came to install the wireless technology for ED monitoring at Samaritan in 2003, they realized that there would be duplication of the wireless access points that the hospital's IT department was already in the process of installing to support the hospital information system (HIS). Everyone at SMC agreed that the wireless initiative had to happen, but installing two wireless network infrastructures would cause major problems.

Unlike RF antennae, which only receive signals from devices, wireless access points both receive and send information from and to each device. With two access points in the same area, patient monitors or laptops would not be able to lock on to just one. The device would try to "talk" to both access points, bouncing from one to the other, and never be able to transmit its data.

Too Much Traffic

Our IT steering committee, which included senior management and physicians, had to carefully balance different interests throughout the hospital, blending both biomedical and information technologies, and always keeping in mind the bottom line goals of improving patient care while maximizing the use of our existing infrastructure.

The key challenge that we needed to address was that there were too many data applications or "vehicles" potentially trying to use the hospital's "information highway" (the network). Since we knew we could not simply add new access points to successfully go wireless, the various departments would have to share the bandwidth. Over the course of 2003-2004, through research into standards-based wireless technology and application data traffic management solutions, we determined that patient monitoring and other HIS applications at Samaritan could co-exist. Because this technological feat had never been accomplished before, it took a full six months to get these systems to work together.

The basis of SMC's solution to our data transport and sharing issues was a VLAN, a network of computers that behave as if they are physically segmented even though they actually share network equipment. VLANs are configured through software rather than hardware, which makes them extremely flexible, allowing network administrators to fine-tune their networks by logically grouping users (in SMC's case, the ED and HIS). We needed to develop a VLAN specific to patient monitoring inside our existing wireless access point network.

The complete solution, which was later trademarked as Infinity OneNet by Drager Medical, uses an IEEE 802.1 lb wireless protocol. The OneNet technology allows both the HIS and the ED to go wireless at the same time, creating two separate "lanes" in the "information highway," one for the less critical, less sensitive applications data, and one dedicated lane for the patient monitoring data.

After much discussion, we agreed to approach the project as experimental, but with an understanding that the existing HIS would not be disrupted. Although the software was being developed on-the-fly, we could clearly see the potential benefit of combining wireless monitoring and the HIS. Drager Medical made the investment in research and development and, beginning in late summer 2003, brought their consultants onsite regularly to set goals and to work out the technical aspects of the wireless solution. By Match 2004, 10 beds within SMC's 22-bed emergency department went wireless.

High Speed Lane

Since SMC's key patient monitoring requirement was that critical alarm messages get through each and every time, we incorporated a device to manage the traffic on the hospital's wireless network. Packeteer, a provider of application traffic management solutions, had developed technology for corporate wide area networks (WANs) in which "packets" or units of digital information could be prioritized and managed appropriately on a network, depending on the application that created the packet. This saved companies from having to buy more bandwidth. We determined that the same concept could be combined with a wireless VLAN network to ensure quality of service on the OneNet system.

The PacketShaper, an intelligent network appliance, would read the priority level of the application involved and control the section of bandwidth allocated to that priority, much like a traffic cop. To route the large amounts of critical data (e.g., waveforms) coming in from patient monitors and keep this separate from other applications' data on SMC's network, it would allow only those packets with a patient monitoring tag to go in the larger, high-priority bandwidth (the equivalent of a "high-occupancy" or "high-speed" lane).

In this way, we were able to prevent the network from bogging down, and allow a continuous flow of critical information. If the administrative applications ever reached a point that maxed out their assigned bandwidth (controlled by the PacketShaper), the transfer rate of that data would automatically slow down.

We first used the PacketShaper to view the data that was already running on SMC's network, packet by packet, from multiple applications. Then we set up the prioritization by application, utilizing the appropriate bandwidths for each.

To test the new wireless system, over the course of a week in early March 2004, 10 monitors and up to seven laptops were set up to transmit a large patient monitoring file including simulated data (ECG, NIBP and pulse oximetry), while running HIS data simultaneously. There was no degradation in information throughput. Then we reversed the process, flooding the normal application bandwidth to see if it affected the monitoring side. Again, there was no overflow, and no loss of quality in the monitoring information.

Benefits of Continuous Access

The transition to the new wireless system was completely seamless for out day-to-day ED staff. To switch from a wired network to wireless, the Ethernet cable was simply removed from each monitor, which automatically changed over to wireless operation. Outwardly, everything else stayed the same.

Today, all 10 of our patient monitors can be moved to any of the 22 beds in Samaritan's ED, and they share the same wireless network used by the 80 HIS laptops located throughout the hospital. Whereas SMC's old telemetry system only captured the patient's heart waveform, now our ED staff has access to all vital signs monitored and recorded continuously via the Wi-Fi access points, with no loss of signal. The nurses do not need to stay with the patient every minute to observe the vitals; instead, they can see the data on a central monitoring screen at the nursing station, or on monitors at the patient's bedside. The PacketShaper continuously monitors the integrity of the network, providing 100 percent connectivity at all times so that alarms reach their intended destination within one second.

The wireless system has increased patient safety by eliminating potential adverse outcomes from a sudden spike in blood pressure. In the past, the nurse might not have observed if a cable had been momentarily unplugged to transport the patient. The new system has eliminated equipment-related safety incidents, whereas before, we experienced one or two of these per month.

By running patient monitoring on our existing network, we also have achieved cost savings through elimination of expenses for installing new wiring, switches to control the signals and specific hardware to run the patient data network.

Although we waited several years for the wireless technology, we were pleasantly surprised at how well everything came together. Now, as the hospital has developed the infrastructure to support wireless monitoring beyond the ED, we plan to expand this capability. Next, we'll extend this capability into the intensive care unit and the progressive care (step-down) units, then throughout the entire hospital within two years.

For more information about Drager Medical's Infinity OneNet solution, www.rsleads.com/512ht-202

Timothy Rhue, C.B.E.T., is lead biomedical equipment technician at Samaritan Medical Center in Watertown, N.Y. Contact him at trhue@shsny.com.

Michael Maloney is director of clinical equipment management at Samaritan Medical Center. Contact him at mmaloney@shsny.com.

COPYRIGHT 2005 Nelson Publishing
COPYRIGHT 2005 Gale Group