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Telemetry Where It Is Now and Where It's Going

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TELEMETRY Where It Is Now and Where It's Going

This network of computer systems displaying patient data via individual radio frequencies can expect to get smaller and more mobile in the future

By Karen Moriarty, MSN, RN, Caroline Campbell, MSEE, CCE, & Sue Apple, DNSc, RN, CCRN

Twenty years ago, a state-of-the-art hospital telemetry system monitored patients' electrocardiograms (ECG) by utilizing a bank of oscilloscopes that tracked one ECG lead at a time. Specially trained monitor technicians were responsible for 24-hour observation of the ECGs.

A further advancement came when oscilloscopes became available on selected units, allowing nurses to view one patient's ECG at a time. Of course, the ECG was not observed in "real time"--the ECG signals were delayed 3-6 seconds. The system had no

capacity for storage of the ECG, meaning there was no capability of recalling a history of the patient's ECG and no permanent record other than the manual recordings obtained by the technician or the nurse. If the monitor technician or the nurse did not record a lethal dysrhythmia at the time of the occurrence, the event was missed and there would be no record of the dysrhythmia.



Telemetry monitoring has made remarkable advances since that time. Modern telemetry systems are a network of computer systems that display patient data via individual radio frequencies. Most systems consist of a central monitoring station and remote viewing stations, which can be interactive or non-interactive. Viewing stations are set up using computers that are interfaced with the central monitoring station. Each monitor can simultaneously display data on several patients. The station can be a remote viewing station that allows nurses and other health care professionals to access patient information, but not make changes in patient settings or configurations. Interactive remote viewing stations allow the user to make setting, configuration and alarm changes. Both stations are connected to the central station through dedicated phone lines that allow easy access to the monitor technicians.



Two types of patient monitors currently are in use. The first is the traditional "box" that a patient wears in a pouch around his neck. The telemetry box typically uses a five-lead ECG system, which enables the system to monitor the patient's ECG in more than one lead.

The second type of monitor utilizes a special link that attaches to a bedside monitor in the patient's room. These links not only transmit the heart rate and rhythm to the ECG monitors at the station, but can also be programmed to record blood pressure, ventilator settings, pulse oximetry, respiration and temperature.

Both types of patient monitors allow for alarm configuration, ECG lead, ST segment monitoring and pacemaker recognition that can be individualized for each patient.

Current computerized telemetry systems are capable of monitoring in real time. The system can record the patient's entire stay in the hospital as well as produce trend reports and ST segment measuring. Some newer systems have the capability to run a 12-lead ECG from the patient monitor.



One problem that continues to plague current telemetry monitoring systems is sporadic signal loss. There are numerous reasons for the sporadic loss of patient signal to which telemetry users have become accustomed. Physical barriers such as walls, doors and even curtains around a patient's bed can prevent clean reception of the signal. Even the patient's body, the caregiver's body and the medical equipment in the environment can be positioned between the patient-worn transmitter and the antenna, thus causing signal loss. Patient signals can also suffer interference from communications devices or from the electromagnetic energy emitted from motors or light ballasts.

The Federal Communications Commission (FCC) is responsible for managing and maintaining orderly and efficient use of the radio frequencies in the electromagnetic spectrum. As part of this task, the FCC must determine who is allowed to use which frequencies and under what conditions.

The FCC's past rulings related to medical telemetry state that telemetry users must not interfere with other licensed users of specific frequencies and must endure any interference imposed from these licensed users.

As the frequency spectrum becomes more crowded with sophisticated communications technology such as pagers, wireless telephones and digital television, it becomes significantly harder to find frequencies within the allotted spectrum that are not susceptible to interference. Just as the need for telemetry is growing in response to rising patient acuity, the amount of spectrum available for telemetry use is rapidly disappearing.

In March 1998, Baylor University Medical Center, located in Houston, directly felt the impact of diminishing spectrum when a digital television station began broadcasting on the same frequencies as used by Baylor's telemetry system. Once the television station was identified as the source of interference, broadcasts were voluntarily stopped until other suitable telemetry frequencies were assessed. However, telemetry monitoring capabilities were temporarily and unexpectedly interrupted as a result of the television broadcasts.



In recognition of the growing urgency of this problem, the FCC requested the assistance of the American Hospital Association to investigate potential solutions. The association formed the Medical Telemetry Task Force, which recommended solutions to the FCC regarding spectrum allocations, bandwidth and coordination of telemetry users. These recommendations were aimed at providing sufficient bandwidth to accommodate growing telemetry needs while protecting telemetry from interference. The recommendations were largely reflected in a Notice of Proposed Ruling issued by the FCC on July 14, 1999. Following a comment period, the FCC is expected to issue its final ruling related to medical telemetry by March 2000.



What can health care providers expect from telemetry systems in the future? Clearly, telemetry is not just for the ECG. Smaller monitors with the capability of storing and transmitting complex data rapidly to multiple remote locations are within our reach. With the expansion of telemedicine, patients may be monitored from their home or workplace, and health care providers at a remote location will be able to interpret the dysrhythmias and direct treatment to the patient. Health care providers will be able to view a patient's ECG rhythm and other vital signs from many locations via their personal computer, allowing for faster intervention for critically ill patients.

With the advent of computerized patient records, telemetry data could be saved in a digital format for subsequent admissions and treatment. Telemetry is fast becoming a critical part of the care of patients now and well into the new millennium. *


Karen Moriarty is clinical manager of Nursing Unit 4NE, Caroline Campbell is the director of biomedical engineering and Sue Apple is the cardiology clinical specialist, all at Washington (DC) Hospital Center.

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