Anesth Analg 2004;98:566-567
© 2004 International Anesthesia Research Society
doi: 10.1213/01.ANE.0000097187.37014.64
EDITORIALS
The Spaghetti Syndrome Revisited
Michael Imhoff, MD PhD
From the Surgical Department, Klinikum Dortmund, Dortmund, Germany
Address correspondence and reprint requests to Surgical Department, Klinikum Dortmund, Beurhausstrasse 40, D-44229 Dortmund, Germany. Address email to mike{at}imhoff.de
The Spaghetti Syndrome is not a new entity in critical care and anesthesia (1). With advances in monitoring and life-support, our most critically ill patients have become trapped in a sheer impenetrable net of wires and tubes, often resembling a plate of spaghetti. This problem is not only a nuisance for the caregiver but can seriously compromise patient safety when cables are inadvertently disconnected or infusion lines snapped off.
Although monitoring cables and sensors are often cited as the culprits of this mess, there are many more cables and lines: dozens of infusion lines, lines from life support and organ replacement devices, and, in surgical patients, numerous drains.
Wireless technology has become a part of daily life outside the hospital, and not only in Scandinavia, where the number of cellular phones is approaching the number of citizens. In many industries, mobile and wireless computing are buzzwords. Wireless networks have been slowly gaining a foothold even in hospitals. It is only recently, however, that they have become standard fare, much like wired Ethernet networks and the Windows computer (2). The explosion of personal digital assistant (PDA) applications and cheap wireless local area network (WLAN) links has raised the consciousness of doctors and nurses who are more and more interested in accessing data on the go without being constrained by an office or a patient bedroom. It is fair to say that wireless technology is also becoming a utility in hospitals. And with the increasing number of wireless monitoring networks on the market, many hospitals may consider wireless technology also in critical care and anesthesia monitoring (3).
There are numerous research projects that go beyond commercially available monitoring networks, in that they try to further miniaturize the monitor and improve wireless communication between monitoring devices in a quest for the truly wearable vital-signs monitor (3–5). Still, in most cases it is necessary to connect the sensor to the monitor via cables. Although these technologies may be exciting, they do not really heal the Spaghetti Syndrome.
The logical next step is to link sensors attached to patients to the monitor using wireless technology, thus getting rid of cables around the patient. There are high-profile research projects (6) that try to address the challenges ensuing from this approach, such as miniaturization, power supply, communications, and wearability. These developments, such as the Body Area Network from the Fraunhofer Gesellschaft (7), may provide some remedy to the Spaghetti Syndrome, at least for noninvasive monitoring without mechanical, hydraulic, or pneumatic components.
Although many research projects have focused on proprietary wireless technology, a new technology appears to lend itself to this problem. Bluetooth, at first sight, is a promising solution "off the shelf" offering free transmission bands, low power consumption, limited range, and sufficient transmission rates.
Bluetooth is a short-range radiofrequency link that operates in the same band as WLAN and microwave ovens (2.4 GHz) and is designed to support cost-sensitive applications, such as printing from a computer without the need for a cable, using wireless headphones for cellular phone conversations, and creating automatic links between laptops on a meeting room.
Bluetooth uses a transmission protocol called "Frequency-Hopping-Spread-Spectrum" (FHSS), which is designed to minimize interference and allow coexistence of several links on the same area. Other protocols that operate in the same band, such as WLAN, use a different protocol called "Direct-Sequence-Spread-Spectrum" (DSSS), which achieves the same goal while supporting a higher overall data rate. When DSSS and FHSS systems are located in the same area, there is an overall degradation of performance (8).
Another issue is interference with medical devices, eventually compromising patient safety. This has been an often-cited issue with cellular phones. However, studies show that this problem may have been overstated, as interference between cellular phones and medical devices appears to be rare (9,10), although when it occurs, it may be critical to patient safety.
In this issue of Anesthesia & Analgesia Drs. Wallin and Wajntraub (11) look into Bluetooth as a potential wireless replacement for monitoring cables around our patients. They specifically studied the interference between Bluetooth and medical devices and conclude that there is no interference affecting the function of medical devices. They also found that medical devices do not interfere with Bluetooth. The authors must be commended for their well-designed study, which shows us that Bluetooth will not put our patients at risk from failure of medical devices. Although Drs. Wallin and Wajntraub have contributed to the body of evidence on medical wireless technology, their study cannot, and was not intended to, answer many technical questions about the use of Bluetooth in the medical context, as they discuss in their article in detail.
Wireless networks are inherently less reliable than their wired equivalents. The license-free open Industrial Scientific Medical band is limited to 80 MHz, and WLAN and Bluetooth have to operate on only 3 non-overlapping 11 Mbps channels in that band. As more devices begin using the same access point, more and more traffic is using the same, limited amount of bandwidth. A patient monitor produces traffic in the order of 10–50 kbps, which is not much when compared with the available bit-rate per channel. A single sensor will produce even less traffic. However, one needs to remember that some installations may have hundreds of devices that may want to operate in the same band (e.g., PDAs), and may also interfere with other signals like Bluetooth. Interference between WLAN and Bluetooth is a well-known problem, by which Bluetooth transmission rates can dramatically be degraded (8). This degradation may even make real-time transmission of monitoring data impossible.
Another essential requirement for use in critical care monitoring is the unambiguous identification of each device in the presence of other devices. Here, cable connections have an indisputable advantage, whereas it is imaginable that a wireless sensor in a crowded intensive care unit or emergency room may transmit one patient’s vital signs to another patient’s monitor. Cables can also be helpful in keeping track of sensors in the hectic critical care workflow.
Moreover, another unsolved problem is the power supply of wireless sensors. Although it is no longer a technological challenge to provide miniaturized devices with adequate battery power, it may be a logistical nightmare for the user to supply hundreds of devices with fresh battery power. This issue, and the issue of comfortable and safe wearability, has been addressed in advanced research and development projects (7) but not yet made available for the broad medical market.
Is Bluetooth the remedy for our Spaghetti Syndrome? Drs. Wallin and Wajntraub have helped us to better understand what Bluetooth and other wireless technologies can do for us. Bluetooth may eventually become part of a solution, but we have to keep in mind that electrical connections are only one ingredient of our spaghetti. There are many fluid- and gas-filled lines, tubes, and hoses that no wireless technology can replace. Therefore, it may even be more beneficial to try to reduce the number of necessary cables and lines by technological means, such as multiplexing to transmit more than one signal through a single cable, and by caregiver discipline and standards of care to arrange cables and lines in a more orderly manner.
Although this may not dramatically reduce the amount of spaghetti, it may make it more palatable to all involved in the process of care.
References
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- Fraunhofer Gesellschaft. Body area network. Available at http://www.ban.fraunhofer.de. Accessed July 13, 2003.
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- Wallin MKEB, Wajntraub S. Evaluation of Bluetooth as a replacement for cables in intensive care and surgery. Anesth Analg 2004; 98: 763–7.[Abstract/Free Full Text]
Accepted for publication September 8, 2003.
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