JOURNAL HOME CME HOME THIS MONTH PAST ISSUES ETOC COLLECTIONS
AUTHORS REVIEWERS EDITORIAL BOARD FEEDBACK RSS HELP
A&A International Anesthesia Research Society
QUICK SEARCH:   [advanced]


     

This Article
Right arrow Abstract Freely available
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Email this article to a colleague
Right arrow Similar articles in this journal
Right arrow Similar articles in ISI Web of Science
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via ISI Web of Science (11)
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Wallin, M. K. E. B.
Right arrow Articles by Wajntraub, S.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Wallin, M. K. E. B.
Right arrow Articles by Wajntraub, S.
Related Collections
Right arrow Equipment
Right arrow Technology
Right arrow Critical Care

Anesth Analg 2004;98:763-767
© 2004 International Anesthesia Research Society
doi: 10.1213/01.ANE.0000097186.99167.BA

CRITICAL CARE AND TRAUMA

Evaluation of Bluetooth as a Replacement for Cables in Intensive Care and Surgery

Mats K. E. B. Wallin, MD MSc*,{dagger}, and Samson Wajntraub, MSc{dagger} Section Editor

*Department of Anesthesiology and Intensive Care, Karolinska Hospital and the {dagger}Division of Medical Engineering, Department of Medical Laboratory Science and Technology, Karolinska Insititute, Stockholm, Sweden.

Address correspondence and reprint requests to Dr. Mats Wallin MD, Department of Anesthesiology and Intensive Care, Karolinska Hospital, S-171 76 Stockholm, Sweden. Address email to mats.wallin{at}labtek.ki.se


   Abstract
Top
 Abstract
Introduction
 Methods
 Results
 Discussion
 References
 
In today’s intensive care and surgery, a great number of cables are attached to patients. These cables can make the care and nursing of the patient difficult. Replacing them with wireless communications technology would facilitate patient care. Bluetooth is a modern radio technology developed specifically to replace cables between different pieces of communications equipment. In this study we sought to determine whether Bluetooth is a suitable replacement for cables in intensive care and during surgery with respect to electromagnetic compatibility. The following questions were addressed: Does Bluetooth interfere with medical equipment? And does the medical equipment decrease the quality of the Bluetooth communication? A Bluetooth link, simulating a patient monitoring system, was constructed with two laptops. The prototype was then used in laboratory and clinical tests according to American standards at the Karolinska Hospital in Stockholm. The tests, which included 44 different pieces of medical equipment, indicated that Bluetooth does not cause any interference. The tests also showed that the hospital environment does not affect the Bluetooth communication negatively.

IMPLICATIONS: Bluetooth, a new radio technology transmitting at 2.4 GHz, was tested in a clinical setting. The study showed that a single Bluetooth link was robust and electromagnetically compatible with the tested electronic medical devices.


   Introduction
Top
 Abstract
 Introduction
Methods
 Results
 Discussion
 References
 
Over the past decade, technical advances have contributed to progress in anesthesia safety. Pulse oximetry and gas analysis have helped decrease morbidity and mortality during anesthesia (1). Improved patient monitoring, as well as increased use of infusion pumps, has introduced a new problem into anesthetic practice, however. Today, a great number of cables and infusion lines are attached to patients. This can sometimes make the care and nursing of the patient difficult, especially during and after transport.

However, it is possible to replace cables with modern wireless solutions. Modern technology, such as miniaturized electronics, makes it possible to manufacture small signal amplifiers, analog/digital converters, and transmitters (Fig. 1). These components can be combined in a small box, placed close to the patient, that wirelessly sends monitoring data to a monitor.



View larger version (145K):
[in this window]
[in a new window]
  		Figure 1. A Bluetooth radio module.

 
Bluetooth is a modern radio technology developed specifically to replace cables between pieces of communications equipment. Bluetooth’s radio link has a range of approximately 10 meters. It can transfer both audio and data with a maximum speed of 720 kbit/s. It transmits in the license-free open ISM (Industrial Scientific Medical) band between 2.4 and 2.48 GHz with a power of 1 mW, which is much less than a modern mobile phone (2,3). As mobile phones, especially older models, can disturb medical devices and are prohibited in many hospitals (4–6), we investigated whether Bluetooth also interferes with medical devices. Higher frequency, lower transmitting power, and robust configuration indicate that it should be possible to use a Bluetooth radio link in an environment with several medical devices.

The aim of this study was to determine whether Bluetooth is a suitable replacement for cables in operating rooms (ORs) and intensive care units (ICUs), with respect to electromagnetic compatibility. The questions to be addressed were:


   Methods
Top
 Abstract
 Introduction
 Methods
Results
 Discussion
 References
 
The study was approved by the ethics committee of the Karolinska Hospital. To conduct the electromag-netic compatibility (EMC) tests, a procedure based on the American ANSI C63.18–1997 standard ("Recommended practice for an on-site, ad hoc test method for estimating radiated electromagnetic immunity of medical devices to specific radio-frequency transmitters") was used (7). The purpose of this standard is to provide health care organizations with an inexpensive, reproducible test method for evaluating the electromagnetic immunity of existing medical devices to different radiofrequency (RF) transmitters. The recommended practice applies to most medical devices and all portable RF transmitters with a power output of 8 W or less. The standard clearly describes how to evaluate the performance of medical devices. Deviation from normal performance (i.e., alarms, error messages or distortion of displayed waveforms) is divided into twenty different categories.

The test equipment consisted of a simulated patient monitoring system. One computer generated continuous simulated samples for the four measurements, electrocardiogram, SaO2, invasive blood pressure, and PCO2. These measurements constitute a realistically sized set of data and correspond well with what is normally monitored on a patient. The samples were sent to another computer via a Bluetooth link (Blue2Space AB, Stockholm, Sweden). The Bluetooth devices had an output power of 1 mW. Both transmitter and receiver were prototypes, which meant that they were neither Communautée Européenne-marked nor electromagnetically shielded.

The tests were divided into three parts. First, a series of laboratory tests were conducted in an empty OR. This gave us an opportunity to test the interference of the medical devices without exposing patients to potential danger. Only after we ensured that the Bluetooth link did not obstruct the interpretation of monitoring data or cause the medical equipment to malfunction could we continue with clinical tests during surgery and intensive care.

The medical devices included in the tests were a selection of different types of medical equipment that are used daily at the Karolinska Hospital. Most devices tested contained electronic circuits that could be affected by electromagnetic fields. In addition, some medical devices that were likely to disturb the Bluetooth communication because of their high emitting power (e.g., diathermy and radiograph) were also included.

In total, 44 different medical devices were tested in the study. They are listed in Table 1.


View this table:
[in this window]
[in a new window]
  		Table 1. Medical Devices Tested for Interference with Bluetooth During the Study
 
Laboratory Tests
The medical device was placed in the middle of the OR in a manner normally used (i.e., on its own stand or, when possible, on a nonconducting table).

The transmitting Bluetooth device was moved in a circle around the medical device. The initial radius of the circle was 1 m. If there was no interference, the radius was decreased to 25 cm and finally 0 cm. To cover as many angles as possible, these tests were performed with both horizontal and vertical circles. The receiving Bluetooth device was placed at a distance of 3 m. The flowchart in Figure 2 describes the test procedure.



View larger version (24K):
[in this window]
[in a new window]
  		Figure 2. Flowchart for the laboratory test procedure.

 
Because the electromagnetic field is strongest close to the Bluetooth device and rapidly decreases with distance, a second test was conducted. In this test, both the transmitter and the receiver were held as close to the medical device as possible (0–5 cm). During the test, we ensured that the Bluetooth devices were as close as possible to sockets and cable ports, as these points were expected to be especially sensitive to interference.

Clinical Tests in the OR
For tests during surgery we chose operations that required as much electrical equipment as possible. The test equipment transmitted continuously during the entire operation, sometimes for up to 4 h. During the course of the surgery, the transmitter and the receiver were moved around in the OR to cover as many positions as possible. Figure 3 shows an example of how the test equipment could be placed during an operation.



View larger version (27K):
[in this window]
[in a new window]
  		Figure 3. An example of the clinical tests conducted during surgery. In this case, a laparoscopic extirpation of an adrenal gland, there are two surgeons and an assisting nurse standing at the side of the patient. The person at the patient’s head is the anesthesiologist. The different positions tested for the transmitter (T) and receiver (R) are indicated.

 
Clinical Tests in the ICU
Tests in the ICU were conducted similarly to the tests during surgery. The test equipment was placed at various locations in an intensive care room during the course of a day. In every room there were between 1 and 3 patients. All patients were connected to several different medical devices. In a normal situation, 3 surveillance monitors, 10 infusion pumps, 2 ventilators, and 1 dialysis machine could be operating simultaneously in each ICU-room. Apart from this equipment, diagnostic devices such as ultrasound and radiograph were used during the course of the day.


   Results
Top
 Abstract
 Introduction
 Methods
 Results
Discussion
 References
 
The tests, which included 44 different electronic medical products (Table 1), showed that none of the tested devices affected the Bluetooth communication. The tests also revealed that Bluetooth did not cause any interference with, or change in operation of, the medical devices.


   Discussion
Top
 Abstract
 Introduction
 Methods
 Results
 Discussion
References
 
Until recently (1/9/2001), the standard for EMC, IEC 60601–1-2 (8), was only specified for electromagnetic waves up to 1 GHz. This means that no electronic medical devices used in hospitals today are tested for disturbances of higher electromagnetic frequencies. It is therefore necessary to do clinical studies of new wireless communications technologies using higher frequencies than 1 GHz, such as General Packet Radio Service (GPRS), Bluetooth, Wireless Local Area Network (WLAN), and Universal Mobile Telecommunications System.

The results of our study show that Bluetooth does not interfere with medical devices. This raises the question of whether the test method was able to detect potential interference. However, we used the same set-up previously to detect disturbances in tests with GPRS. Therefore, we are confident that the test results are correct.

In our study, 44 different medical devices were exposed to the Bluetooth radio link. Compared with previously published reports of interference of common wireless technology, this is a relatively large selection of medical devices (4,5,9,10). The tests indicated that Bluetooth does not cause any interference. The tests also showed that the hospital environment does not interfere with the Bluetooth communication. Even during the use of diathermia, which can emit an electrical field as high as 1000 V/m close to the active cable, the Bluetooth communication remained intact.

Hence, our study indicates that the Bluetooth technology is electromagnetically compatible with the tested medical devices and may decrease the number of cables used around patients.

Another advantage of Bluetooth communication is the possibility to display monitored data in an OR on one or several wirelessly connected mobile monitors placed wherever is most convenient for the OR personnel.

However, although our study has shown that interference between Bluetooth and medical devices does not seem to occur, Bluetooth should be introduced with caution in a hospital setting for several reasons. First, considerable work has to be done to ensure that a Bluetooth-based patient monitoring protocol designed for anesthesia and intensive care is highly robust. The protocol must be designed so that data integrity is guaranteed and so that data from patients lying nearby cannot be recorded by mistake. Therefore, further investigations with multiple Bluetooth links transmitting data in the same room are necessary.

There might also be problems with other Bluetooth devices entering and attempting connections to the Bluetooth patient monitoring net. Appropriate encryption protocols are necessary and must be integrated in a Bluetooth-based monitoring system. Second, interference between Bluetooth and wireless computer networks, WLAN (802.11b) (11), is well known (12,13). As Table 2 shows, both WLAN and Bluetooth operate in the same license-free open ISM-band, 2.4–2.48 GHz. Co-existence of Bluetooth and WLAN is possible (12,13), but they affect each other and the throughput of data is decreased. In fact, in some situations WLAN can block the data transfer from Bluetooth. WLAN is already used at some hospitals for patient data management. If a Bluetooth net and a WLAN are thoroughly and carefully designed, they should be able to cooperate (12). However, neither WLAN access points nor Bluetooth modules should be installed close to microwave ovens (14).


View this table:
[in this window]
[in a new window]
  		Table 2. Technical Comparison of Bluetooth and WLAN (IEEE 802.11b)
 
This, in combination with the fact that Bluetooth is still a new and relatively untested technology, leads us to recommend that each hospital conduct its own tests in its own working environment before introducing Bluetooth products in potentially sensitive settings.

Why not use WLAN instead as a cable replacement? Today’s WLAN transmitters consume more power (100 mW), are not as small as the Bluetooth modules, and are also more expensive. We therefore believe that Bluetooth is better suited for cable replacement solutions.

With regard to EMC, we conclude that Bluetooth has the technical capabilities that are necessary to be a part of a patient monitoring system. However, interference between Bluetooth and WLAN (IEEE 801.11b) can occur. This implies that communications protocols and system designs must be carefully prepared. We therefore recommend that wireless networks in hospitals should be controlled by the hospital’s technician and not always be open to the public. Our study does indicate, however, that Bluetooth technology can decrease the number of cables around the patient.


   References
Top
 Abstract
 Introduction
 Methods
 Results
 Discussion
 References
 

  1. Brodsky JB. What intraoperative monitoring makes sense? Chest 1999; 115: 101S–5.[Abstract/Free Full Text]
  2. Bluetooth core specifications, v1.1. Overland Park, KS: Bluetooth SIG, 2001.
  3. Bray J, Sturman CF. Bluetooth—connect without cables. Upper Saddle River, NJ: Prentice Hall, 2001.
  4. Hietanen M, Sibakov VH, Hällfors S, et al. Safe use of mobile phones in hospitals. Helsinki: Finnish Institute of Occupational Health: Technical Research Centre of Finland, 2000.
  5. Tri JL, Hayes DL, Smith TT, Severson RP. Cellular phone interference with external cardiopulmonary monitoring devices. Mayo Clin Proc 2001; 76: 11–5.[ISI][Medline]
  6. Isao B, Hiroshi F, Takashi K, et al. Experimental study of electromagnetic interference from cellular phones with electronic medical equipment. J Clin Eng 1998; 23: 122–34.
  7. Institute of Electrical and Electronics Engineers, Inc. American national standard recommended practice for an on-site ad hoc test method for estimating radiated electromagnetic immunity of medical devices to specific radio-frequency transmitters (standard C63.18). Piscataway, NJ: IEEE, 1997.
  8. IEC 606–1–2, collateral standard: electromagnetic compatibility— requirements and tests. Geneva: International Electrotechnical Commission, 1993.
  9. Tan KSH, I. Effects of a wireless local area network (LAN) system, a telemetry system and electrosurgical devices in a hospital environment. Biomed Instrum Technol 2000; 34: 115–8.[Medline]
  10. Rice WP. 2.4 GHz RF WLAN EMI in medical devices. J Clin Eng 2000; 25: 260–4.
  11. Institute of Electrical and Electronics Engineers, Inc. Wireless LAN medium access control (MAC) and physical layer (PHY) specifications: higher-speed physical layer extension in the 2.4 GHz Band. Piscataway, NJ: IEEE, 1999.
  12. Lansford J, Nevo R, Manello B. Wi-Fi (802.11) and Bluetooth simultaneous operation: characterizing the problem. San Diego, CA: Mobilian, 2000.
  13. Berggren M. Wireless communication in telemedicine using Bluetooth and IEE 802. 11b. Uppsala: Uppsala University Department of Information Technology, 2001: 32.
  14. Hanada E, Hoshino Y, Oyama H, et al. Negligible electromagnetic interaction between medical electronic equipment and 2.4 GHz band wireless LAN. J Med Syst 2002; 26: 301–8.[Medline]
Accepted for publication September 8, 2003.




This article has been cited by other articles:


Home page
 Anesth. Analg.Home page
K. Oyri, I. Balasingham, E. Samset, J. O. Hogetveit, and E. Fosse
Wireless Continuous Arterial Blood Pressure Monitoring During Surgery: A Pilot Study
Anesth. Analg., February 1, 2006; 102(2): 478 - 483.
[Abstract] [Full Text] [PDF]

Home page
 Anesth. Analg.Home page
R. G. Soto, L. F. Chu, J. M. Goldman, I. J. Rampil, and K. J. Ruskin
Communication in Critical Care Environments: Mobile Telephones Improve Patient Care
Anesth. Analg., February 1, 2006; 102(2): 535 - 541.
[Abstract] [Full Text] [PDF]

Home page
 Eur. J. Cardiothorac. Surg.Home page
A. Beuchat, S. Taub, J.-D. Saby, V. Dierick, G. Codeluppi, A. F. Corno, and L. K. von Segesser
Cybertools improve reaction time in open heart surgery
Eur. J. Cardiothorac. Surg., February 1, 2005; 27(2): 266 - 269.
[Abstract] [Full Text] [PDF]

Home page
 Anesth. Analg.Home page
M. Imhoff
The Spaghetti Syndrome Revisited
Anesth. Analg., March 1, 2004; 98(3): 566 - 567.
[Full Text] [PDF]

This Article
Right arrow Abstract Freely available
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Email this article to a colleague
Right arrow Similar articles in this journal
Right arrow Similar articles in ISI Web of Science
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via ISI Web of Science (11)
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Wallin, M. K. E. B.
Right arrow Articles by Wajntraub, S.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Wallin, M. K. E. B.
Right arrow Articles by Wajntraub, S.
Related Collections
Right arrow Equipment
Right arrow Technology
Right arrow Critical Care

Lippincott, Williams & Wilkins Anesthesia & Analgesia® is published for the International Anesthesia Research Society® by Lippincott Williams & Wilkins with the assistance of Stanford University Libraries' HighWire Press®. Copyright 2006 by the International Anesthesia Research Society. Online ISSN: 1526-7598   Print ISSN: 0003-2999 HighWire Press