Tiêu chuẩn iso tr 21730 2007

Microsoft Word C044865e doc Reference number ISO/TR 21730 2007(E) © ISO 2007 TECHNICAL REPORT ISO/TR 21730 Second edition 2007 02 15 Health informatics — Use of mobile wireless communication and compu[.]

Terms and definitions

For the purposes of this document, the following terms and definitions apply

Hz unit of frequency of electromagnetic energy based upon the emitted wavelength

2.1.2 decibel dB relative ratio, one-tenth of the common logarithm of the ratio of relative powers, equal to 0,1 B (bel)

NOTE 1 The ratio in decibels equals 10 lg 10 (P 1 /P 2 )

NOTE 2 Decibels as above, but relative to a fixed 1 mW of power, are sometimes indicated as dBm.

Abbreviated terms

ASHE American Society for Healthcare Engineering

AAMI Association for the Advancement of Medical Instrumentation

Copyright International Organization for Standardization

Provided by IHS under license with ISO

ANSI American National Standards Institute

CDRH Center for Devices and Radiological Health, Department within FDA (US)

CISPR International Special Committee on Radio Interference

COMAR IEEE Committee on Man and Radiation

FDA Food and Drug Administration (US)

IEEE Institute for Electrical and Electronics Engineers

IVDs In vitro diagnostic devices

JCAHO Joint Commission on Accreditation of Healthcare Organizations

LAN Local Area Network, including 802.11b and 802.11a systems

MHRA Medicines and Healthcare Products Regulatory Agency (UK)

PAN Personal Area Network, including 802.15.1 (Bluetooth), 802.15.4 (Zigbee), 802.15.3a, etc

R&TTE Radio and Telecommunications Terminal Equipment

RF Radiofrequency, classically defined as ranging from a few kHz - 300 GHz

Rx Reception, received RF signal

Tx Transmission, transmitted RF signal

UWB Ultra-wideband, refers to RF transmissions spread over at least 500 MHz of spectrum or a fractional bandwidth of > 0,2, with a very low spectral density at any given frequency (−41,3 dBm/MHz)

V/m Volts per metre, a measure of RF electrical field strength

WiFi Wireless Fidelity Network system

3 Current status of management of electromagnetic interference

Mobile wireless equipment in healthcare facilities

The increasing use of mobile wireless devices by healthcare professionals is essential for enhancing point-of-care communication and patient information, ultimately reducing medical errors and improving healthcare delivery Additionally, patients and visitors are finding personal mobile phones and wireless devices invaluable, particularly during emergencies These wireless technologies encompass a range of devices, including mobile phones, handheld computers, WiFi networks, wireless modems for laptops, and personal area networks such as Bluetooth and Zigbee, as well as two-way pagers and radios.

Table 1 highlights various wireless technologies utilized in healthcare facilities, indicating that mobile wireless equipment can operate on exclusive licensed frequencies, like mobile phones and two-way radios, or on unlicensed ISM bands at 900 MHz, 2.4 GHz, 5.2 GHz, and 5.8 GHz, as seen with cordless phones and wireless data networks From an RF signal perspective, these transmitters utilize either simple analog or complex digital technology Mobile wireless equipment is categorized into three groups based on output power: the first includes IEEE 802.11 and IEEE 802.15 systems that transmit at lower power levels (< 10 mW); the second comprises two-way radios and pagers with higher constant power (1 W to 5 W); and the third consists of dynamically power-controlled devices that adjust their transmission power between a few milliwatts and 2 W based on network signal strength This report does not delve into RFID tags in healthcare, which, while operating in HF (13.56 MHz) or UHF (915 MHz) bands, typically emit low energy and are primarily used for asset tracking rather than mainstream communication technology.

An Institute of Medicine (IOM) report has estimated that common medical errors may contribute to between

In the US, annual deaths are estimated to range from 44,000 to 195,000, with similar figures for the UK and Australia Recent reports highlight the potential of wireless technology to enhance communication and access to patient data at the point-of-care This advancement could lead to fewer billing errors, lower costs associated with land-line phone systems, and improved home-based monitoring and long-term care.

Concerns about electromagnetic interference (EMI) from radiofrequency (RF) emissions have led many healthcare organizations globally to adopt precautionary policies that limit wireless equipment usage in their facilities These policies vary, with some organizations imposing selective restrictions on mobile wireless equipment, while others allow more unrestricted use However, overly restrictive policies can hinder the advantages of wireless technology in healthcare, whereas unmanaged RF emitter usage may pose significant and unnecessary risks to patients.

Table 1 — Current and developing wireless technologies that may be used in healthcare facilities

Type of device Intended application Transmitted frequency (Tx) Maximum transmit power

W-LAN (Local Area Networks — WiFi)

5,15 to 5,8 GHz 40 mW [5,15 to 5,25 GHz]

2,4 to 2,462 GHz (North America), 2,412 to 2,472 GHz (Europe), 2,471 to 2,497 GHz (Japan) typical app's: constant ~10 mW, but spec allows for:

2,4 to 2,48 GHz (US, Europe, Japan) typical app's: constant ~10 mW, but spec allows for: 1 W [US],

100 mW [Europe], 10 mW/MHz [Japan]

Europe), 2,447 to 2,473 GHz (Spain), 2,448 to 2,482 GHz (France), 2,473 to 2,495 GHz (Japan)

Powerclass I: 100 mW Powerclass II: 2,5 to 10 mW Powerclass III: 1 mW

UWB in 3 to 10 GHz band ~0,6 mW spread over 100's of MHz

Sensor Networks, Low-Latency Data/Control

Europe), 2,412 to 2,472 GHz (Europe), 2,471 to 2,497 GHz (Japan) typical app's: constant ~1 mW, but spec allows for: 1 W (US),

100 mW (Europe), 10 mW/MHz (Japan)

Fixed Broadband Wireless Access Systems (Video + simultaneous voice

Watts — potentially higher transmit power in licensed bands as compared to more restrictive unlicensed bands

Mobile unlicensed and licensed Broadband Wireless Access Systems (Video + simultaneous voice

Watts — potentially higher transmit power in licensed bands as compared to more restrictive unlicensed bands

Broadband Wireless Access Systems (Video + simultaneous voice

& data) licensed bands below 3,5 GHz Watts

AMPS 824 to 849 MHz (US), NMT 453 to 458 MHz (Europe), TACS 890 to 915 MHz (Europe), JTACS 832 to 925 MHz (Japan)

AVG PWR: 0,6 to1 W down to

~6 mW in steps of −4 dB

& 1710- to 1785 MHz (Europe, Asia), iDEN 806 to 824 MHz (US), Tetra 380 to 400, 410 to 430, 450 to 470 & 805 to 870 MHz (Europe), PDC 810 to 826 & 1429 to 1453 MHz (Japan)

AVG PWR: 200 to 600 mW down to 20 to2 mW in steps of −1 to

−4 dB, PEAK PWR 1 to 2 W (depending upon the technology)

AVG PWR: 250 mW to ~1 uW in

1,92 to 1,98 MHz (Europe, Asia), 1,7 to 2 GHz (US) AVG PWR: 250 mW to < 1 mW in steps of 0,25 - 1 dB

Type of device Intended application Transmitted frequency (Tx) Maximum transmit power

1750 to 1780 MHz & 1,92 to 1,98 GHz (Europe, Asia)

AVG PWR: 250 mW to < 1 mW in steps of 0,25 to 1 dB

Two-way pagers WAN Text

Cordless Phones Analog and Spread Spectrum

2,4, 5,8 GHz (US), Spectralink 2,4 GHz (US, Europe), CT-1 30-

AVG PWR: constant 10 mW, some units up to 1 W

2,4 to 2,462 GHz AVG PWR: constant 10 mW

Periodic and continuous transmissions, 300 to 900, 2400 to 5800 MHz

Periodic and continuous transmissions, 400 and 800 MHz

Periodic and continuous transmissions, 426 to 449 MHz

Wired Network, specifically the 802.3 Hard Line Ethernet, serves as a reliable alternative to wireless technologies While it is not a wireless solution, wired Ethernet remains the current standard, though it is gradually being supplanted by various wireless options This comparison highlights the ongoing evolution of networking technologies.

The risk of patient harm due to EMI

The unmanaged use of mobile wireless devices in healthcare facilities has increased despite existing policies While published reports indicate that the risk of accidental electromagnetic interference (EMI) events is relatively low, there may be significant underreporting of such incidents Anecdotal evidence has linked suspected EMI events to various medical devices, including ECG and EEG machines, ventilators, and infusion pumps Additionally, ad hoc studies have validated these concerns.

Electromagnetic (EM) interference can affect sensitive medical devices due to certain wireless transmitters, but this typically occurs only under specific conditions, such as high power transmission, close proximity, and prolonged exposure Notably, significant interference is uncommon with RF transmitters operating at a constant output power of 100 mW or less.

The second edition of IEC 60601-1-2 sets general immunity levels of 3 V/m for non-life-supporting medical equipment and 10 V/m for life-supporting devices; however, manufacturers in the US and other countries can justify lower levels, leading to a lack of consistent international regulation Many mobile wireless handsets can exceed these limits when at maximum power and close to medical devices, and older devices may not meet current EM immunity standards Despite the risks associated with unmanaged mobile wireless handset use, most equipment could still operate safely alongside sensitive medical devices if effective management procedures are established.

Existing relevant standards and recommendations

The International Electrotechnical Commission (IEC) has established standards (IEC 61000-x-x) for EMI mitigation and testing, with specific relevance to medical devices outlined in IEC 60601-1-2 This standard mandates that life-supporting medical equipment must withstand field strengths of 10 V/m, while non-life-supporting devices should endure 3 V/m within the 80 MHz to 2.5 GHz frequency range Additionally, medical equipment manuals emphasize the necessity of maintaining distance from radio-frequency sources IEC 60601-1-2 also defines emission limits and immunity test levels for various electromagnetic disturbances, based on CISPR and TC 77 standards Despite many manufacturers adhering to these guidelines, there is a lack of government regulation enforcing them in regions like the US, and older medical devices may not meet current immunity standards The IEC standard allows for lower immunity levels under certain justifications, particularly for patient-coupled equipment, acknowledging that some physiological signals may be significantly lower than those induced by a 3 V/m field strength.

The European Community has established medical device directives to enhance electromagnetic immunity compliance for devices in Europe Directive 93/42/EEC mandates that non-implanted medical devices be designed to minimize risks from environmental conditions, including magnetic and radiofrequency fields Additionally, the general directive 89/336/EEC applies to medical device safety for devices not covered by specific directives Relevant directives also exist for active implantable devices and in vitro diagnostic devices (IVDs) The recent Radio and Telecommunications Terminal Equipment (R&TTE) Directive outlines testing protocols and RF immunity levels for terminal equipment within the EU, covering apparatus that includes medical devices as defined by 93/42/EEC or active implantable devices under 90/385/EEC This directive aims to streamline the market entry for radio and telecommunications terminal equipment manufacturers while ensuring compliance with medical device regulations However, many mobile wireless transmitters operating at full power may still exceed the established IEC standards.

10 V/m immunity level at distances up to 1 m away, and well exceed the general 3 V/m immunity test level [11]-

The American National Standards Institute has introduced a quick and affordable ad hoc test protocol that healthcare organizations can use to evaluate electromagnetic compatibility (EMC) between mobile wireless equipment and medical devices This protocol enables organizations to swiftly gather data for informed decision-making regarding wireless equipment policies, while also ensuring a standardized approach for comparing results across various testing locations.

The Association for the Advancement of Medical Instrumentation (AAMI) has published a Technical Informational Report (TIR) that serves as a vital guideline for healthcare organizations, simplifying the concept of electromagnetic compatibility (EMC) for non-engineering staff This report outlines how significant electromagnetic interference (EMI) from medical devices can occur and offers strategies for risk management Building on previous studies by the American Society for Healthcare Engineering (ASHE), it provides insights into assessing the radiofrequency (RF) environment and includes a model EMC/EMI policy The key recommendations from AAMI TIR 18 are available on the FDA Center for Devices and Radiological Health (CDRH) website.

The IEEE Committee on Man and Radiation (COMAR) has highlighted concerns regarding electromagnetic interference (EMI) from mobile phones affecting life support equipment, urging medical device manufacturers to enhance their devices' resilience against rising radio frequency (RF) fields However, the manuscript offers minimal guidance for healthcare organizations on effectively managing this risk.

The American Medical Association (AMA) highlights the risks associated with mobile wireless equipment in healthcare facilities, particularly its potential impact on medical equipment when used nearby Although current clinical reports of electromagnetic interference (EMI) are rare and mostly anecdotal, suggesting a minimal risk, the diversity of communication signals and medical devices complicates electromagnetic compatibility (EMC) predictions The AMA advises acquiring newer medical equipment designed to withstand external radio frequency (RF) emissions, conducting ad hoc testing according to the ANSI/IEEE C63.18 protocol, and implementing straightforward management procedures to ensure compliance with existing EMC standards They emphasize the importance of ongoing vigilance against EMI by clinical engineering teams and medical staff, while not endorsing a blanket ban on wireless devices Additionally, while ECRI suggests maintaining a one-meter distance from mobile phone-type transmitters, the AMA calls for further discussion among EMC experts on this matter.

In 1998, the University of Oklahoma Center for the Study of Wireless EMC published a manual for healthcare facilities, which included key recommendations sourced from Segal The manual emphasizes the importance of ad hoc testing and education, advocating for the development of a comprehensive EMC policy, the creation of mobile handset exclusion zones, and the implementation of EMI reporting procedures It also advises on enhancing the immunity of medical devices and maintaining specific separation distances: up to 6 meters for standard radios, 2 meters for common mobile phones, and 0.3 meters for in-building LAN and cordless phone systems.

Health Canada's Medical Devices Bureau has conducted extensive testing on various RF transmitters, including mobile phones and Bluetooth devices, and found that while improper use of mobile phones and radios can cause interference, most low-power transmitters do not significantly threaten medical devices under normal conditions In 1994, the Bureau organized a roundtable to establish a US-Canadian Task Force on Electromagnetic Compatibility in Health Care, led by Dr Bernard Segal from McGill University The recommendations emphasized promoting wireless technology in healthcare, proactive management of electromagnetic compatibility (EMC) issues by hospital engineering teams, and suggested actions such as managing medical devices, reducing RF transmitter power, labeling vulnerable devices, educating staff, and upgrading to more resilient medical equipment when feasible.

The Health Council of the Netherlands recommends a precautionary separation distance of 1.5 meters from mobile phones, noting that there have been no documented cases of mobile phones interfering with sensitive medical equipment Despite this, many healthcare facilities in the Netherlands implement blanket bans on wireless communication devices primarily as a precautionary measure.

The UK’s Medicines and Healthcare Products Regulatory Agency (MHRA) advises that the use of GSM and TETRA mobile phones in healthcare facilities should adhere to local policy guidelines Additionally, they emphasize that any on-site interference from emergency services radios should be considered secondary to the risks involved in managing incidents.

The American Hospital Association (AHA) and the American Society for Healthcare Engineering (ASHE) advocate for the managed use of resources in healthcare facilities, as outlined in their recent recommendations While the Joint Commission on Accreditation of Healthcare Organizations (JCAHO) does not provide specific guidelines, it evaluates whether healthcare facilities are effectively implementing their own Environmental Management Control (EMC) policies during accreditation reviews.

The US Army Center for Health Promotion and Preventative Medicine advises the maintenance of medical device inventories, education on electromagnetic compatibility (EMC), proper signage, and reporting of electromagnetic interference (EMI) Additionally, it recommends restricting personal wireless equipment in critical care areas and limiting wireless devices in the emergency room to only those essential for medical treatment, ensuring they are kept more than 3.3 feet away from medical devices.

A recommended practice document by the Consumer Electronics Association (CEA) establishes a standard icon and terminology for the disabled use of mobile phones and personal electronic devices Originally created in 2004 to aid flight attendants in monitoring device usage on commercial flights, this document is currently undergoing revisions to achieve ANSI accreditation For more information, visit [CEA's website](http://www.cea.org/).

The CEA Home Networking group (R7, wg11) suggests that healthcare facilities consider adopting standardized terminology and icon recognition in their policies, especially in public areas where non-controlled RF transmitters are restricted However, the use of these devices in a "transmit disabled" state, which permits access to internal software, games, and address books, is permitted.

Figure 1 — Consumer Electronics Association icon for transmit-disabled use of mobile phones

Medical device electromagnetic interference (EMI) can arise from various RF sources, including neighboring medical devices, not just mobile wireless equipment The International Special Committee on Radio Interference (CISPR) 11 standard outlines emission limits for industrial, scientific, and medical (ISM) equipment, detailing measurement methods for electromagnetic emissions within the 150 KHz to 18 GHz frequency range, as well as frequencies with no emission limits Consequently, medical devices that do not intentionally emit RF energy are unlikely to disrupt other equipment that adheres to the relevant electromagnetic compatibility (EMC) immunity standards.

Overall requirements for risk management of medical devices over the entire life cycle (design, manufacture, service, distribution, use) are outlined in ISO 14971 [54] and are relevant.

EMC with medical devices and minimization of EMI risk

Medical device manufacturers are encouraged to enhance the electromagnetic (EM) immunity levels of their devices due to the increasing radiofrequency emissions in healthcare environments It is essential for manufacturers to aim for and, where feasible, surpass the current IEC immunity standards of 3 V/m and 10 V/m, as these levels can be exceeded by various mobile wireless transmitters operating at higher power levels nearby Furthermore, manufacturers and vendors of wireless technology in healthcare should offer information and support to achieve electromagnetic compatibility (EMC) with medical devices.

The following recommendations aim to guide healthcare organizations in leveraging mobile wireless technology effectively while managing electromagnetic compatibility (EMC) issues to reduce risks Healthcare facility staff may oversee various wireless systems, including peer-to-peer devices like two-way radios and local area systems such as cordless phones.

The management of various mobile wireless systems, including WiFi/IEEE 802.11b and wide area networks like mobile phones and PDAs, is essential for healthcare facilities These recommendations emphasize the importance of selecting the right technology to meet communication and computing needs, achieved through thorough testing, effective system design and engineering, proper medical device management, and clear user guidelines.

To ensure electromagnetic compatibility (EMC) and prevent interference with medical devices, healthcare facilities must adopt specific recommendations for non-controlled wireless communication equipment While managing controlled mobile wireless systems used by healthcare staff is feasible, it is often impractical to apply the same management strategies to wireless devices brought in by visitors or patients Consequently, healthcare organizations may find it unfeasible or undesirable to implement management procedures for these controlled systems In such instances, it may be more appropriate to establish restrictions on the use of wireless devices in areas with a high concentration of sensitive medical equipment, particularly life support systems.

General recommendations

To ensure electromagnetic compatibility (EMC) with medical devices while implementing wireless RF technology, healthcare facilities should establish a comprehensive management, testing, procurement, and education program This approach is based on guidelines from AAMI TIR 18-1997, the AMA Council on Scientific Affairs, and the American Society for Healthcare Engineers The program must address both controlled and uncontrolled wireless emitters, such as patient or visitor devices By following specific recommendations, as illustrated in Figure 2, facilities can develop strategies that allow wireless equipment to function effectively while managing and mitigating potential electromagnetic interference (EMI) issues.

Important recommendations are made equally to medical device manufacturers, healthcare facilities and wireless equipment manufacturers

Risk management for medical devices is governed by ISO 14971 This standard applies to all medical devices, including systems that incorporate wired or wireless communication devices Compliance with ISO 14971 must be maintained throughout the entire life cycle of the device.

Medical device manufacturers must consistently meet and surpass the electromagnetic immunity levels outlined in IEC 60601-1-2 when designing new equipment Additionally, devices not explicitly addressed by this Technical Report should still adhere to relevant consensus standards regarding electromagnetic compatibility (EMC), particularly for active implanted devices and in vitro diagnostics As mobile RF and wireless transmitters become more prevalent, it is anticipated that medical devices will increasingly function in such environments.

Healthcare facilities must effectively manage wireless equipment by adhering to established guidelines, ensuring that the use of beneficial technology is not unnecessarily restricted while also addressing potential electromagnetic interference (EMI) issues It is essential to integrate recommendations for electromagnetic compatibility with medical devices into corporate policies, strategic plans, and governance models.

Wireless equipment manufacturers must thoroughly understand potential electromagnetic interference (EMI) issues that may occur in worst-case scenarios involving medical devices and other wireless technologies It is essential to implement their equipment and systems in alignment with established recommendations to mitigate these risks effectively.

Figure 2 — Relationship of user groups to use strategy

Responsibility within healthcare facilities

In healthcare facilities, clinical and biomedical engineers, along with other relevant technical staff such as those in spectrum management, IT, telecom, and building services, should serve as the primary resource for electromagnetic compatibility (EMC) and electromagnetic interference (EMI) mitigation, as well as for EMC/EMI education and training While this Technical Report does not specify qualifications, it emphasizes the importance of considering the education, expertise, and experience of the individuals responsible for these critical functions.

Inventory within healthcare facilities

Effective management of medical device inventory in healthcare facilities is crucial to ensure compatibility with the growing RF environment When purchasing new medical devices, it is essential to prioritize equipment that meets or exceeds the EMC immunity requirements outlined in IEC 60601-1-2:2001 or other relevant standards Additionally, older devices that are particularly vulnerable to EMI from mobile wireless transmitters should be phased out as budget allows While significant modifications to medical devices are not advisable, simple precautions can mitigate EMI risks For instance, positioning cables, sensors, and electrical accessories to increase their distance from RF transmitters can help reduce susceptibility, especially for life-supporting devices or those known to be sensitive to EMI.

`,,```,,,,````-`-`,,`,,`,`,,` - © ISO 2007 – All rights reserved 11 to EMI can be positioned away from high traffic areas or adjoining rooms where mobile wireless equipment may be in routine operation.

Testing within healthcare facilities

The IEEE/ANSI C63.18 protocol is essential for on-site testing of mobile wireless equipment in healthcare settings, acknowledging that exhaustive testing is often impractical due to varying needs and resources Key recommendations include prioritizing testing on life-supporting medical devices and older equipment, conducting periodic tests annually or after significant changes, and focusing on high-power mobile devices if comprehensive testing is unfeasible Collaboration with larger healthcare facilities and accessing ad hoc EMI testing databases can provide valuable insights when testing is limited Manufacturers and network providers can assist with testing setup, while independent third-party evaluations may enhance the impartiality of EMI assessments Devices identified as susceptible to EMI should be replaced with those compliant with IEC 60601-1-2:2001, although susceptibility to emissions from mobile devices remains a concern Lastly, ad-hoc testing results can vary significantly, serving primarily to identify devices at risk rather than providing a quantitative measure of susceptibility.

Controlled use within healthcare facilities

To ensure the safe use of controlled mobile wireless equipment by healthcare professionals, it is essential to implement effective procedures for identifying, characterizing, and mitigating potential electromagnetic interference (EMI) issues The recommended practice outlined in IEEE/ANSI C63.18 serves as the ideal test protocol for conducting rapid, on-site RF EMI testing to address these concerns.

Testing must be conducted with the mobile wireless handsets intended for use in the controlled system as test transmitters For multiple in-house systems, it is essential to test each distinct RF signal Additionally, when new in-house systems are introduced, each unique RF signal should undergo testing, as varying RF signals can lead to different electromagnetic interference (EMI) effects.

Ongoing ad hoc testing is essential, requiring the maintenance of records for EMI test results, characterization of new medical device acquisitions, and thorough investigation and verification of reported EMI incidents, while also ensuring that policies are adjusted as needed.

Regular periodic testing is essential, ideally conducted annually, particularly following the introduction of new communication devices, medical equipment, or significant changes in positioning.

Given the qualitative nature of ANSI C63.18 ad hoc testing, it is advisable to implement nominal management policies, including recommended minimum separation distances, even in the absence of significant EMI issues For mobile handsets that operate at a constant output power without dynamic power control, such as standard two-way radios and 802.11 systems, effective EMC management should ensure sufficient separation from sensitive medical devices In cases where radio transmitters have a high constant power output of 1 W or more, considerable separation distances may be necessary, potentially leading to restrictions on their use in specific areas of healthcare facilities.

In environments with low-power wireless devices like pagers and Bluetooth equipment, the risk of electromagnetic interference (EMI) is generally lower compared to two-way radios, although testing is still advisable For mobile transmitters, effective electromagnetic compatibility (EMC) management should include network characterization and in-building engineering to ensure that devices transmit at appropriate power levels to minimize EMI Healthcare facilities may have areas with inconsistent signal coverage, leading to fluctuations in handset transmit power, which should be assessed and managed Medical device management may involve labeling, repositioning, or replacing susceptible devices, with modifications only made by manufacturers due to regulations Additionally, user guidelines should recommend maintaining a separation distance of 25 cm to 2 meters between mobile devices and sensitive medical equipment For comprehensive EMC/EMI management, the AAMI TIR 18 is a valuable resource.

Testing of specific fixed-infrastructure components, such as local electrical circuits and circuit breakers, is essential if their failure poses a significant hazard and can be conducted safely Healthcare facilities must actively manage spectrum usage by maintaining a list of all controlled-use RF sources, indicating their authorized operating areas and the maximum number of units allowed in each zone Additionally, it is crucial to address wireless security issues, as neglecting them could jeopardize patient safety if the informatics system is compromised.

Non-controlled use within healthcare facilities

Non-controlled mobile wireless devices, brought into healthcare facilities by visitors, patients, or staff, emit various signals at different power levels It is essential to implement distinct EMC/EMI management policies for these devices, separate from those for controlled mobile handsets Although ad hoc testing and management solutions are beneficial, they may not be feasible for all wireless systems.

In healthcare facilities, the compatibility of mobile handsets varies, with some posing a higher risk of electromagnetic interference (EMI) due to differences in output power and signal types As the variety of handsets increases and new models integrate multiple technologies, distinguishing between RF transmitter types by appearance alone becomes challenging The rise of wireless headsets and accessories further obscures the visibility of RF transmitters, complicating the situation Many mobile devices can transmit various signal types, including data transmission through different technologies Given the diverse operating frequencies and power outputs of wireless devices, enforcing policies based on visual identification of non-controlled mobile handsets is impractical Therefore, all non-controlled mobile wireless handsets should be subject to the same management and restrictions, regardless of their visual similarities to controlled devices.

Restrictive policies should mandate that individuals refrain from using personal mobile wireless devices in areas where sensitive medical equipment is present This can be effectively communicated through clear signage or other reliable methods, urging users to turn off non-controlled mobile devices before entering zones with critical life-supporting medical devices Even well-meaning individuals may be tempted to answer calls or messages, making these precautions essential for patient safety.

To enhance the implementation and enforcement of restrictive policies in healthcare facilities, clear signage should be placed in areas where sensitive medical devices are present This will inform patients and visitors about the facility's policies Additionally, establishing designated zones with easy access for the use of wireless handsets can help ensure that the operation of these devices does not disrupt medical equipment.

Restrictive policies regarding mobile wireless communication in healthcare facilities must strike a balance between assessing electromagnetic interference (EMI) risks and addressing the increasing demand for mobile connectivity among patients, visitors, and staff Although some facilities may consider banning all non-controlled mobile devices, such actions could be excessive and fail to meet the urgent communication needs during emergencies Additionally, while advising patients and visitors to maintain a safe distance from medical devices may theoretically reduce EMI risks, implementing such guidelines can be impractical in many areas of the facility.

Minimum separation requirements should not be the primary management strategy for life-supporting medical devices However, distances established through ad hoc testing can serve as an additional management layer in areas where these devices are frequently used.

RF emissions from network sources

To effectively manage RF emissions from in-building system network antennas, such as WAN microcells, repeaters, and LAN access points, it is crucial to position them in locations that ensure adequate separation distance to reduce the impact of electromagnetic interference (EMI) on medical devices Ideal placements include the roofs of corridors and rooms.

RF emissions from base station sites situated on the rooftops or structures of healthcare facilities must adhere to national radio regulations to ensure that emissions are limited within the supporting building.

Medical devices within healthcare facilities

The placement and operation of RF-emitting medical devices in healthcare settings require careful consideration due to their use of electromagnetic energy Various medical devices, such as electric scalpels, physio-diathermy units, and ultrasound machines, generate RF and microwave fields for functions like cauterization and deep tissue heating For instance, electric scalpels produce RF fields, while physio-diathermy units may emit frequencies like 915 MHz and 2,450 MHz, and ultrasound machines can radiate frequencies ranging from approximately 3 MHz to 20 MHz It is essential for healthcare facilities to exercise caution regarding the use of these emitters near other sensitive medical devices.

Electromagnetic security and inventory systems, including metal detectors, anti-theft systems, and RFID, can emit signals that may interfere with sensitive medical devices It is essential for healthcare facilities to establish policies and practices that address the potential impact of this equipment For instance, RFID tags in healthcare settings may act as passive emitters, becoming active when near RFID readers However, these readers can generate strong magnetic fields and should be considered as transmitters in both ad hoc testing and EMC/EMI management policies Relevant guidelines can be found in ASTM F 2401-04.

Patients using medical devices at home, like dialysis equipment, blood glucose analyzers, and infusion pumps, should be instructed to keep a minimum distance of 1 meter between these devices and any mobile wireless equipment during operation to ensure safety and proper functionality.

A.1 Propagation of RF energy through space

Radio frequency waves, ranging from 300 KHz to 300 GHz, propagate through space at the speed of light The relationship between frequency and wavelength in a vacuum is defined by the equation: frequency (MHz) multiplied by wavelength (meters) equals the speed of light, which is approximately \(3 \times 10^8\) m/s.

RF electromagnetic energy can impact medical devices situated far from the RF source Interference is more probable at RF frequencies where the components of medical devices, such as cables and circuit board traces, are odd multiples of 1/4 of the wavelength Additionally, in strong RF fields or with sensitive circuitry, effects may be noted for conductors that are significantly shorter or longer, even down to about 1/20 of the wavelength.

RF energy consists of electric (E) and magnetic (H) fields, typically measured in volts per meter for the electric field and amperes per meter for the magnetic field In the near field, where the distance from the source is small relative to the wavelength, measurements focus on electric or magnetic field strength based on the field being assessed At frequencies below 100 MHz, these measurements are generally taken in the near field, where E and H field strengths decrease with distance from the source However, in close proximity to sources like cellular phones, field strengths can be significantly high.

Unintended coupling of electric (E) fields to medical devices can happen via straight cables, wires, and printed circuit board traces, even at significant distances from the RF source In contrast, unintended coupling of magnetic (H) fields typically occurs through coiled cables, wire loops, and loops in printed circuit board traces, usually in close proximity to the RF source.

In the far field, where the distance exceeds the sum of several wavelengths of the transmitter's carrier frequency, the field strength from a transmitter decreases inversely with distance By knowing the output power of the transmitter, the dipole equation can estimate the field strength in this region as a function of distance Understanding the radiated RF immunity is crucial for effective transmission.

An estimation of immunity for a medical device can be achieved by substituting immunity for the field strength in the dipole equation, expressed as Ρd Κ = Ε, to solve for distance.

P is the the output power of the transmitter, in watts;

E is the the immunity of the medical device, in volts per metre; d is the the minimum separation distance, in metres;

K is a constant in the range of 0,45 to 7, depending on the antenna efficiency of the transmitter

The value of K for mobile phones is approximately 7, and the value for lower-frequency hand-held transmitters such as walkie-talkies can be as low as 3

This approximation is not valid at distances shorter than several wavelengths of the transmitter carrier frequency, specifically in the near field The limitations of this estimate will be discussed further.

⎯ a single transmitter is present, radiating at its maximum rated power;

⎯ the worst-case susceptibility of the medical device occurs at the frequency of the transmitter

When multiple RF transmitters, such as mobile phones, are in use, the required minimum separation distance for compatible operation may exceed the calculated value Conversely, if a single RF transmitter operates below its maximum power or if the medical device's worst-case susceptibility occurs at a different frequency, the actual minimum separation distance could be less than the calculated distance Factors such as antenna efficiency, radiation patterns, and the presence of absorbing or reflecting objects, including buildings and people, also influence the actual minimum separation distance Additionally, multipath reflections may necessitate a greater separation distance, while absorption could lead to a reduced distance compared to the calculated value.

Mobile phones function on wide area networks (WANs) that consist of various cell sites utilizing different RF signal technologies The first generation (1G) analog technology, such as AMPS in the US, NMT in Scandinavia and parts of Russia/Eastern Europe/Mid East/Asia, and TACS in Europe, has become largely obsolete Many of these systems, along with smaller networks in countries like France, Germany, Italy, and Canada, are being phased out in favor of newer digital technologies that dominate the market today.

Analog technology allocates a unique channel frequency to each user, whereas second generation (2G) digital technologies enable multiple users to share a single channel frequency This advancement increases network capacity by converting voice data into binary form (0's and 1's) and compressing it.

Second-generation technologies in the US encompass traditional CDMA (Code Division Multiple Access) and various TDMA (Time Division Multiple Access) technologies, such as NADC (North American Digital Cellular), which is being phased out, along with GSM (Global System for Mobile) and iDEN (Integrated Dispatch Enhanced Network) In contrast, GSM is the dominant technology in Europe, parts of Asia, and other regions, while Tetra (Terrestrial Trunked Radio) is widely utilized by public safety departments across many European countries.

CDMA technology transmits compressed data in small segments across 40 contiguous channels, utilizing approximately 1.2 MHz of frequency spectrum, allowing multiple calls to overlap Each call is distinguished from the noise created by other users on the same channel through a unique sequence code This innovative approach forms the foundation for emerging third-generation communication technologies.

Tiêu đề	Health Informatics — Use Of Mobile Wireless Communication And Computing Technology In Healthcare Facilities — Recommendations For Electromagnetic Compatibility (Management Of Unintentional Electromagnetic Interference) With Medical Devices
Trường học	International Organization for Standardization
Chuyên ngành	Health Informatics
Thể loại	Technical report
Năm xuất bản	2007
Thành phố	Geneva

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