Telemetry Via Wi-Fi: A Case Study

Abstract

Cardiac telemetry monitoring systems have changed significantly over the years. Introduced in the 1970s, these systems were originally fairly straightforward. Patients wore transmitters that sent dedicated analog signals to receivers connected with coaxial cable and routed back to a wiring closet. Most systems were typically monitored on the unit by a telemetry technician or nursing staff.Since the first system was installed, many changes have occurred with this technology, including the creation of the Wireless Medical Telemetry Service (WMTS) and IEEE 802.11 wireless technology, centralized monitoring environments, remote alarm notification via paging and wireless phones, additional measurement parameters, etc. In addition to the changes to telemetric technology, a proliferation of other wireless medical device technologies has occurred, including infusion pumps and vital sign monitors.Provena Health, a Catholic healthcare system with six acute care sites located throughout Illinois, has experienced the evolution of telemetry monitoring first-hand. In 2007, Provena Mercy Medical Center (PMMC), a 356-bed hospital located in the western Chicago suburb of Aurora, Illinois, embarked on a project to replace its existing telemetry system. This older system was a 608–614 MHz system with 32 channels on the fifth floor of the facility (Figure 1). The system was linked to a paging system that was no longer supported by the manufacturer and provided limited alarm notification to the nursing staff. The fifth floor of this facility is dedicated to cardiac patients. Nursing staff conducted the central monitoring on the unit; there was no centralized telemetry monitoring solution.The facility identified the need to create a centralized approach to monitoring and expand the total number of telemetry channels for peak census periods. The need to improve the alarm management and increase patient safety was identified as a priority. The facility ultimately decided to replace the existing telemetry system with a new 80-channel telemetry system that utilizes a pre-existing secured wireless network (Wi-Fi). The first phase of this project was to replace the 32 channels on the fifth floor and relocate the central monitoring function to an existing central telemetry center (CTC).Rather than installing an all-new proprietary infrastructure, training all new personnel, finding a new location for the CTC, and remodeling locally, the hospital decided to take advantage of new technology by utilizing the existing non-proprietary infrastructure and transmitting the data to the central telemetry center (CTC) at Provena Saint Joseph Hospital (PSJH), a sister site approximately 28 miles away. We decided to accomplish this by deploying a second set of central stations at the sister facility and transmitting the data between facilities over the WAN (Wide Area Network).The proposed system takes advantage of the existing data infrastructure. This infrastructure was installed by the hospital information systems (IS) department and allows secure and reliable transmission of data using non-proprietary wireless and hardwired technology. The wireless network already supported other wireless medical devices, such as computers on wheels and noninvasive vital signs monitoring. Plans call for it to also support a system-wide voice over Internet protocol (VoIP) phone solution. The use of existing infrastructure provided a significant cost savings for the new system (Figure 2).We began the equipment selection process with a site visit to Avera Heart Hospital of South Dakota, the first location in the United States to deploy this new 80-channel telemetry system. The team visiting the site included nursing, clinical engineering (CE), IS, and hospital administration. The goal of the visit was to discover how the clinical staff tailored the system and how the wireless network was configured at the site.The wireless network at Avera consisted of several Cisco 1242 Access Points (AP) operating in an autonomous mode. It was configured for 802.11 b/g support for a variety of small, portable, low-power wireless devices, and was designed as a general purpose wireless network. Provena's network (Figure 2) used Cisco Wireless Services Module (WiSM) blade controllers to control the Cisco AP1131AG and 1242AG Access Points across the entire facility with a 6509 Core. This network was also configured for 802.11b/g support for a variety of small, portable, low-power devices, and designed as a general purpose wireless network.Both networks had compatible access points and provided the same functionality; the routing of the traffic was different due to the difference of autonomous control versus central control of the access points. Virtual local area networks (VLANS) were created on the wireless network and all the traffic from the application was routed to the central stations so it could be displayed and collected for full disclosures, and sound alarms as detected. The system worked well, and provided this site with the ability to see the electrocardiogram (ECG) waveforms at the bedside and manage alarms. Our team therefore determined it was possible to recreate this type of system, and that it would work well if the wireless network was installed and configured correctly.Our equipment selection and configuration decision was based on several factors. Compatibility with existing equipment at the CTC, as well as the ability to use the existing WAN to provide network connectivity at a remote site, were two primary considerations. We also considered the features available in the new devices. The new transmitters, known by the manufacturer as patient-worn monitors, are unlike conventional telemetry products that process ECG signals in a separate receiver that detects alarms and analyzes arrhythmias. The new system detects ECG alarms and arrhythmias onboard the transmitter, just like a conventional bedside monitor. The transmitters feature a rechargeable battery, a local display, and alarms. The device is a complete monitoring system and utilizes the hospital's 802.11 wireless network to communicate to the central station. The onboard display allows the clinician to see ECGs and pulse oximetry readings at the bedside, not just at the central station, so clinicians no longer have to leave the room to see a patient's ECG rhythms.This multidisciplinary project involved CE staff at both sites, site-based IS staff, corporate IS staff, and clinical staff. The local IS director and I co-led this project, working with the telemetry equipment manufacturer, corporate IS staff, and clinical staff. Since the project affected both sites, we had to determine the key members of the team and define their roles and responsibilities. The IS director for the site took the lead in coordinating all meetings, creating and tracking issues throughout the project, and coordinating with corporate IS for support. The CE manager and local staff primarily oversaw equipment installation at both sites, facilitated end-user training, and worked closely with the networking team during and after the equipment installation.The team consisted of stakeholders and management responsible for installing, configuring, using, and supporting the system after it was deployed. The manufacturer provided a project manager to create a project plan that helped to define roles, responsibilities, and timelines. Corporate IS staff was responsible for configuring and supporting the connections between facilities, the switches at all locations, and the wireless network at all sites. Local IS staff were responsible for local infrastructure, IP address management, and first call support for network connectivity issues. Biomedical equipment technicians (BMET) at each site were responsible for the equipment deployed at each location and identifying user issues and first line support. Clinicians at both locations actively managed the patient alarms, and direct phone lines from the CTC were put in place to facilitate communications to all telemetry units at both locations. The alarm management and communication protocols are the same for each location.One of the group's challenges was ensuring corporate IS understood the technical requirements for the product and the ongoing support needed after the installation was complete. Since this was a relatively new product, the group could use only limited technical documentation early on in the project. In addition, the Wi-Fi system had been categorized as a tier 3 system by IS, which defined their response time for service-related requests and acceptable down time. Once we started using the Wi-Fi system for a critical patient, we changed the monitoring of the Wi-Fi system to a Tier 1 system support level, which required a phone response and on-site response from IS within 60 minutes.The first task required was a validation survey of our Wi-Fi network and our hardware infrastructure. Global Technology Resources Incorporated (GTRI), a wireless and network consulting company specializing in wireless integration projects, conducted the survey. This survey was executed with the available wireless survey tools and consisted of the measurement of signal strengths at all locations from all access points to ensure optimum coverage of the patient care area. They also evaluated the WAN connection between PSJH and PMMC Aurora.One early concern was whether there would be any latency between the primary site and the CTC. Since the CTC was staffed full-time to monitor the patients and was responsible for notifying the clinical staff at the unit of critical alarm events, it was imperative there be no delays. IS was also concerned about the bandwidth required to support the system. The users were concerned about the reliability of the network connection to the CTC. The hospital enabled multicast routing across the enterprise, allowing the data created at one central station to be forwarded to a second central station at the CTC. Latency times were found to be negligible, and the total bandwidth needed for 80 beds was less then 8 megabits per second (Mbps).In Figure 3 you can see the entire network showing the routes and VLAN id for the different networks. The data was routed on our core network from the primary site to the central IS server farm, and to the sister site where the CTC was housed. It has backup devices and redundant data links at each location. There is even a backup data link between the primary and sister site. In addition to hardware and network redundancy, a Quality of Service (QoS) solution was also implemented to ensure optimum performance of the wireless network. The new devices require the same level of support as a wireless phone to ensure the data arrives in sequence.The day of go-live consisted of deploying the new equipment, configuring the central monitoring stations, removing old devices, and assigning patients to the new system. Since we were using the existing Wi-Fi system, patients and staff were only minimally disrupted. We were able to utilize the existing telemetry system right up to the point where we switched patients off of the old system and on to the new one. Understandably, the switch produced a certain amount of tension. Approximately 20 minutes after our initial go-live, corporate IS changed the data rate on the wireless controllers, which caused a loss of communication between the telemetry transmitter and the APs. This was one of many lessons learned regarding what types of changes we can make to the wireless network and the impact they have on the system. It was also a heads-up to make sure we defined a clear change request process. In response, we created a technical document of the entire system, including details on IP addresses, servers, routers, switches etc. IT must now notify clinical staff when network changes are made, and plan outages and updates to minimize network downtime.After our go-live and our first glitch, the system was relatively stable for the first few days. Then, our CTC staff started to notice random gaps in the wave forms in the full disclosure data. The dropouts appeared on various patients at different times of the day and many times while the patients were in their rooms. Based on our initial site evaluation, we expected to see some dropout while a patient was in transport to various support areas, such as radiology, stress, and even to elevators, since we did not have APs in the elevators (see sidebar on ASME A17.1 code, which prohibits installation of APs in elevators or shafts). We expected the signal to be rock solid when the patient was on the unit. Our initial troubleshooting showed that in some of the patient rooms, the transmitter was not maintaining connectivity to the closest AP. After further troubleshooting, we discovered that the AP power levels were changing, and in some cases the APs were overpowering the environment, causing the telemetry transmitter to maintain connectivity to an AP that was not the best source based on physical location.After working with IS and our Cisco consultant, we learned that the Wi-Fi system utilized a feature called Radio Resource Management (RRM). RRM regularly analyzes the existing radio frequency (RF) environment, adjusting AP power levels and channel configurations to help load balance and provide maximum bandwidth for each client. It can also help provide automated self-healing functionality to compensate for RF dead zones and AP failures. Portable wireless devices have a relatively low output to conserve battery life (30mW maximum), and are sensitive to channel and power level settings on the APs.To correct the dropouts, we updated the Cisco firm-ware and set some APs to fixed channels and power levels as requested in the original assessment. We then reviewed the configuration settings again, and determined that some data rate changes needed to be updated. We resurveyed the area with Air Magnet (an enterprise wireless network security and troubleshooting application; www.airmagnet.com, Sunnyvale, CA) and confirmed signal strengths. After fine tuning the environment, we eliminated our dropouts on the floors. It's important to note that the new telemetry devices (or patient-worn monitors) have arrhythmia and alarm detection, along with an integrated display and speaker. Whenever the device is “off-line,” it monitors the patient locally, stores events, and uploads stored events once communication is re-established with the Wi-Fi network.We learned a significant lesson regarding the difficulty of isolating issues within a dynamic Wi-Fi environment. I'll admit there was some finger pointing early on in this project. We realized we had to establish a new procedure for clinical staff to report problems with the system. It was not clear to the clinical staff at the CTC or on the unit whether to report problems to CE, IS, the local CE staff, or the other site. Once we redefined the rules, we established that all issues with the system would be reported to the CE call center. The call center was staffed during normal business hours and had an automated system for after hours and weekend calls. The CE technician would assess the problem and take ownership for resolving it, regardless of where the problem existed. In addition, we created a decision tree for them to isolate the source of the problem and determine if we needed to engage IS. IS also had a call center and, whenever a call was created, a work order was generated.The new system and configuration dramatically improved nursing's ability to quickly respond to patient needs and greatly reduced time spent on documentation. Both patient and associate satisfaction scores have significantly improved. The new system enabled quick deployment of additional telemetry beds throughout the facility by eliminating the need to install a dedicated telemetry antennae system. We estimate a cost savings of $300,000 by utilizing the existing Wi-Fi network. We also reduced the number of full-time equivalents (FTE) for the CTC by combining the two sites into one CTC solution.The overall project was a success; however, we all recognized opportunities for improvement and the need for a more formalized approach to deploying this new technology. Listed below are key take-aways from the project that I hope will help others undergoing a similar project: