|Telemetry systems monitor patients remotely, often from the nurse’s station, and give patients mobility that can provide a mental boost.|
Telemetry troubleshooting presents itself as a classic process of elimination. When something goes wrong, most biomeds start with the transmitter and work their way through the signal path, eliminating options, until they arrive at the problem. Often, they don’t have to go too far down the path. “Most problems we have are with the transmitters, but for the most part, our telemetry systems are pretty reliable,” says Wayne Unger, BMET specialist with Summa Health Systems in Akron, Ohio.
Telemetry systems should be reliable. They are used to monitor patients remotely so that adverse outcomes are avoided or minimized. In many facilities, remotely often means from the central station or nurse’s station. There, someone can keep a watchful eye on these patients as they move about the floor or complete physical therapy. Patient mobility makes life easier for the patient and the nurse. Patients can do simple things, such as use the bathroom, without the help of a caregiver. They can also receive a mental boost—a patient not tethered to the bed may feel a bit freer and a bit healthier.
Wireless telemetry is particularly valuable in stepdown units, including those serving surgical and cardiac rehabilitation patients. “These patients have come out of the ICU and are mobile but still need to be monitored,” says Jeff Biffle, CBET, outreach technical assistant, cardiovascular imaging, St John Heart Institute, Tulsa, Okla. “Telemetry works well in permitting us to monitor their heart rate while they are walking in the hall or during their exercise rehabilitation regimens.”
Doug Graham, SMS Inc, Westbrook, Me, a representative for Life Sensing Instrument Company (LSI), Tullahoma, Tenn, sees many units used for short-term monitoring of post-MI or other cardiac patients during exercise sessions. “Patients come, are given a transmitter, and can walk about the room as they perform their exercises while a nurse monitors them,” he says.
Graham notes that many facilities hold about four to 16 transmitters in their inventory to serve units like this. Larger facilities may use more. Biffle estimates that at the St John Heart Institute, there are twice as many stepdown units as ICUs. “We have about 250 telemetry channels in the hospital, of which 130 are hardwired beds,” Biffle says.
The History of WMTS
In 2000, wireless medical telemetry service (WTMS) was given its own bandwidth—608 MHz to 614 MHz, as well as 1396 MHz to 1400 MHz and 1427 MHz to 1432 MHz—by the Federal Communications Commission (FCC) to avoid interference with new digital television stations. The 1427 MHz to 1432 MHz range is shared with nonmedical telemetry operations, such as utility telemetry operations, but holds primary rights in most markets.
That same year, the FCC also established regulations covering the use of this spectrum. The American Society for Healthcare Engineering of the American Hospital Association (ASHE/AHA) was selected by the FCC to serve as the exclusive WMTS frequency coordinator.
ASHE/AHA maintains a database of WMTS equipment used by heath care providers, who are required to register with the organization. The database helps to determine which frequencies are available in any geographic area, and it contains information about the location, operating frequency, emission type, effective radiated power, equipment manufacturer, and model number for each device.
ASHE/AHA services are available on a first-come/first-served basis and do not include frequency conflict resolution. This is left to the users, although the FCC Enforcement Bureau will make the final decision in disputes with no resolution.
For more information, visit the FCC Web site at wireless.fcc.gov or the ASHE/AHA Web site at www.ashe.org.
Unger sees their use increasing. “When I first came to Akron City Hospital about 4 years ago, we had about 56 telemetry units. Now, we have 110 and will add 21 more at the beginning of the year,” Unger says. He attributes the increase to two factors: cost and need—or the physicians’ desire to monitor patients.
“If you want to acquire ECG information from a patient, you can use a bedside monitor, but the instrument will cost about $10,000 to $25,000,” Unger says. “At a cost of $2,500, transmitters are a lot cheaper.”
Subsequently, they are also more available. “Physicians want to be able to get an ECG on a patient, but unless that patient is in a critical care area or a telemetry bed is open, it’s difficult to do,” Unger says. “So we are adding telemetry units to provide that service.”
Telemetry unit components characteristically include a transmitter, a receiver, an antenna, and the display station. “Telemetry units are pretty much the same,” Biffle says. “Different manufacturers have different specialties, but they do pretty much the same thing. Physiological signals are gathered from the patient and transmitted through the air to a receiver that processes the information into a visual display.”
The transmitters are generally small, usually about the size of a cell phone. Patients may carry them in a pouch on a belt loop or in a pocket. Pads and wires hook the patient to the transmitter and enable it to collect the data. The most common parameter is ECG. Blood pressure, breathing rate, temperature, and oxygen saturation levels (Spo2 and METS) can also be measured on some systems. Alarms can be set to go off at certain parameters to alert caregivers to problems. Some data storage may also be possible. At Summa, data is kept for 24 hours. After that time, it is overwritten.
Over the past decade, most facilities have replaced their analog systems with digital. “I’m not too sure anyone still uses analog, and part of the reason is that analogs require sophisticated equipment to tune the transmitters, whereas changing the frequency is easy on digital devices,” Unger says.
No matter how many units a facility has, service and repair is often handled in-house. Problems involving boards or software are sent back to the manufacturer, but most other issues can be resolved by in-house biomeds. “Some shops do repair down to the component, but if they don’t handle full service in-house, they most certainly handle first call,” Biffle says.
Even if the biomed cannot handle a repair, he can swap out components, for instance a motherboard or a transmitter. “They can pull out a board if the receiver goes bad and put in a new one, then send the bad board to us for repair,” Graham says.
In-house care provides a faster response and is less expensive—usually. “I used to repair our transmitters,” Unger says. “But they are now obsolete, and it’s cheaper to send them out than to try to find and buy the parts.”
Maintaining the Best Approach
Unger believes the best approach to service and repair of telemetry units is to attend the training offered by the vendor. “Everyone does things a little bit differently, and there are certain things you won’t know unless you attend the training,” he says.
Preventive maintenance (PM) is fairly simple: regular and thorough cleaning. “As a whole, there is a lot of linen and dust in the hospital environment,” Biffle says. “The linen, sheets, towels, bedspreads, blankets, all put out a lot of lint. The computer fan will suck that up, and the lint will find a home in the computer.” He recommends cleaning the computer—vacuuming it out—quarterly (“at least biannually,” he says).
Unger cleans his receivers four times per year and the central station computer twice annually. Graham also recommends biannual cleaning. The regular cleaning prevents the computer from overheating.
Biffle also performs a check of the device’s function twice per year. “I hook the transmitters to a simulator, run a known signal through, and verify that the known signal is what you get on the display,” he says. “So if I set the simulator at a heart rate of 60 with normal sinus rhythm, then that is what I should see on the display. It verifies the transmitter, receiver, acquisition unit, and computer are working properly.”
PM is much easier with telemetry compared with bedside units. “I have one floor with 40 telemetry units, which translates to about 150 pieces of equipment, yet I only spend a few hours a year up there,” Unger says.
Telemetry units tend to be reliable. Common problems include the lead wires, pads, and damage associated with size. The transmitters, for example, are often easily dropped or accidentally placed in the laundry. Lead wires can break, electrodes can become dry and brittle, and sweat can cause corrosion. It is also easy—and not uncommon—for patients to forget about the transmitter and walk away with it.
Interference does not tend to be a problem once the frequency is set. According to Biffle, wireless medical telemetry, or WMTS, is within the 608 MHz to 614 MHz band. Most facilities transitioned to the 600-MHz range with no trouble. “If you do your homework prior to installing the system and adhere to the frequencies assigned to you, then the possibility of cross-talking is minimized,” Biffle says. This homework should include checking with the IT department to make sure there is no crossover use of bandwidth. “IT can also put filters on the wireless network, which can cause problems,” Biffle says.
Graham uses a spectrum strength analyzer to check a frequency for interference or feedback when first setting the system up. “If there is interference or feedback, we just change the frequency,” Graham says. “Once it’s up and running, we generally don’t have any problems.”
When there is a problem, some troubleshooting may be required. Biffle notes the process is the same, whether the trouble is interference or performance and whether the unit is hardwired or telemetry.
Most biomeds start with the basics. “Is the battery dead? Are the lead wires hooked up correctly?” asks Graham, who describes the method as a process of elimination. If all is working properly, the next step is to hook a simulator to the telemetry transmitter and run a known signal. If the signal looks fine, Biffle walks around with the transmitter and wiggles the wires to see if there is any adverse effect on the display. “Doing this, you are actually looking for broken wires or bad connectors,” Biffle says. If that works, Biffle checks connections to the patient to make sure that he or she was hooked up properly.
“In 95% of cases, if you can get a wave on the waveform viewer, then there is probably nothing wrong with the transmitter and more troubleshooting is necessary,” Unger says.
The next step may be to check the transmitter itself by testing it on a different frequency. Biffle’s system permits him to switch to an auxiliary transmitter to perform this test. “We have a 16-unit system with two banks of channels,” Biffle says. “Each channel is capable of processing a primary and an auxiliary transmitter, so if there are problems on one channel, I can switch to the auxiliary channel with a few keystrokes to test a known signal. If the auxiliary transmitter works, then the problem resides in the primary transmitter.”
If the problem still exists, then the solution is elsewhere. Biffle next checks the frequency and receiver end by testing the transmitter on a different frequency. “Each receiver card in my system processes four channels, so if the transmitter doesn’t work on channels one through four, but does operate on five through eight, then the board in the PC that is processing the bad channels is probably the problem,” Biffle says.
If the problem is found on all 16 channels, then the antenna system may be the cause. “You have to judge if you are getting what you are expecting to see,” Biffle says. He suggests that many times users expect more out of a system than is possible, so it is up to the biomed to know how a system is supposed to be used, what it is capable of, and to relay that information to the users. And when the system is not performing to these specifications, then it is a process of elimination to discover why.
Renee Diiulio is a contributing writer for 24×7. For more information, contact .