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This publication is available at https://www.gov.uk/government/publications/electromagnetic-interference-sources/electromagnetic-interference-sources
Electromagnetic interference (EMI) can affect several types of medical devices that have electrical or electronic systems. Examples of devices that can be affected include:
- pacemakers or defibrillators – implanted or external
- ECG monitors
- infusion pumps
We recommend that hospitals/trusts develop local policies to minimise the risk of interference with critical medical equipment.
There are many sources of EMI in hospitals and healthcare environments but the ones most likely to cause problems with certain medical devices include:
- emergency vehicle/services radios
- diathermy (electro-surgery)
- mobile phones
- radiofrequency identification (RFID) devices
2. Emergency vehicle/services radios
These types of radios are used in emergency service vehicles, including ambulances.
Radio communications emit very strong electromagnetic waves and pose the highest risk of EMI with sensitive medical devices. They can have an effect at a distance of 5 meters.
This means you should find out if sensitive equipment is used in the buildings close to parked ambulances. You should also:
- carry out a risk assessment before sensitive medical devices are used inside an ambulance and repeat if there are any changes to the vehicle radio system
- external pacemakers are especially susceptible to EMI – position the pacemaker as far as possible from the vehicle’s aerial(s); there should be a warning notice inside the ambulance to show the position of the aerial(s)
- ambulance, paramedic, cardiac and accident and emergency staff should be trained to recognise common interference events, and act appropriately
3. Diathermy (electro-surgery)
This can affect active devices such as:
- implanted pacemakers
- cardioverter defibrillators
- cochlear implants
Interference generated by monopolar surgical diathermy is more severe than that generated by bipolar diathermy and can be sufficient to temporarily inhibit pacemaker output, cause a temporary increase in pacing or cause a loss of programmed settings.
4. Mobile phones
We do not recommend a ban on the use of mobile phones in hospitals. However, a mobile phone can affect sensitive equipment if it is closer than 1 metre.
Therefore we recommend that hospitals/trusts develop local policies to minimise the risk of interference in places such as:
- treatment areas such as:
- intensive therapy units (ITU)
- special care baby units (SCBU)
- operating theatres
- accident and emergency departments
- by the patient’s bedside when the patient is connected to any electro-medical device
- other areas where interference with a device could have a detrimental effect on patients
5. Radiofrequency identification systems
Radiofrequency identification (RFID) devices are used in healthcare establishments to trace and track equipment. They can also be used in a patient’s hospital bracelet.
RFIDs consist of 2 parts: a tag (which may be active or passive) and a detector (‘reader’). They are becoming more commonly used.
The level of interference from RFIDs is similar to that from mobile phones. They may cause problems with sensitive electronic medical devices such as pacemakers and monitors if they are closer than 1 metre.
Hospitals/trusts should do a risk assessment before using this technology and will need to decide on areas of restriction. We recommends caution; avoid using these technologies in critical care areas such as intensive therapy units (ITU), special care baby units (SCBU) or where patients are attached to complex devices.
The risk of interference from RFIDs is influenced by:
- type or power output of the reader
- type or power rating of the tag (active tags only)
- carrier frequency
- distance between reader and medical device
- location of use: in a store room there is a low or no risk, in an operating theatre the risk is higher
6. Airport security
We are not aware of any interference problems between security body scanners and sensitive medical devices such as:
- implanted pacemakers
- implanted cardioverter defibrillators (ICDs)
People with these implants should walk through metal detectors normally and not wait in the detection zone
As with mobile phones, keep a distance of 15cm (6 inches) between a hand-held screening wand and the implanted device.
Patients should carry their device registration card to show to staff when passing through security checks.
Recently introduced airport security body scanners use high-frequency electromagnetic waves to scan a body. These electromagnetic waves pass through clothing and are reflected by the skin. They do not enter the body and so would not interfere with implanted electronic medical devices.
7. Non-EMI interference
The functions of active devices such as implanted pacemakers, cardioverter defibrillators and cochlear implants can be affected by fixed magnets. They can interfere by activating the magnetic reed-switches of the device.
Small, fixed magnets are in a range of objects such as:
- security tags on clothes in shops
- fastenings on mobile phone cases, clothes and jewellery
The effects can cause asynchronous mode pacing in pacemakers and inhibition of shock therapy in implantable defibrillators.
The risk is negligible as long as the item isn’t put too close to the implant (ie not closer than 3cm). So for example, headphones should not be placed in the breast pocket of a shirt or jacket, or draped around the neck, even when not in use.
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