Pacemakers & welding; do you know the risks?

By Robert Shaw, TWI, UK

While the general term ‘pacemaker’ is used, there are several different devices which can be considered to be at risk of electromagnetic interference. For example, there are both pacemakers which are intended to provide a continuous signal to maintain a regular heartbeat, and cardioverter defibrillators, which are intended to give a “shock” if a heart problem is detected. It is not possible to give a completely definitive answer when asked about the risks to a pacemaker user of being exposed to the electromagnetic fields associated with welding. Each pacemaker is programmed for its user’s specific needs, and each case needs to be treated separately. Pacemakers vary in their sensitivity from type to type, maker to maker and individual to individual. Defibrillators, for instance, are far more sensitive to electromagnetic radiation than single chamber pulse rate control pacemakers. Studies have shown that devices using unipolar sensing are more prone to interference than those using bipolar sensing when used around a MIG/MAG welding power source1.
A pacemaker user who is 100% pacemaker dependent is also at greater risk than a user who only needs the pacemaker for short periods of time, e.g. if suffering from a condition such as postural hypotension.

Working near electromagnetic fields

Working in the vicinity of equipment which produces very strong electromagnetic fields, such as resistance welders which produce pulsing magnetic fields, and particularly where the pulsing rate matches or is close to the pulse rate of the pacemaker user, can be a hazardous situation.
In the presence of pulsing magnetic fields, the pacemaker can be fooled into thinking that the heart is beating normally and does not need assistance. In this case it may switch off, with the risk of cardiac arrest and collapse. Or it may cause the pacemaker to think the heart is beating inconsistently and cause it to deliver continuous stimuli. Removal from the magnetic field will result in the pacemaker returning to its normal, programmed condition.
Exposure to very strong magnetic fields can clear the memory of the pacemaker. With more modern pacemakers, it is possible that they will reset to a default condition and pulse continuously until re-programmed. The electromagnetic fields from resistance welding processes can be variably high, so using this equipment is not recommended. Cardioverter defibrillators may respond to random currents (whether variations in DC or AC) by delivering an inadvertent shock therapy. It is also important to consider secondary risks in this scenario, for example a welder may drop a welding torch or workpiece, or touch hot material. With regards to ‘conventional’ arc welding, such as MMA, MIG/MAG or TIG, the risk of the magnetic field generated by the welding process interfering with the function of the pacemaker depends on a range of factors. These include both the earlier comments about pacemaker variability, but also some general trends regarding the welding process. Pulsing or AC welding is of greater concern to an equivalent current DC welding process, as is HF interference.

Guidelines for welders

Manufactures of pacemakers and other bodies have developed guidelines regarding use of welding with a pacemaker^2-5, as summarised below.

■ Limit welding current to less than 160 Amps.
■ Work in a dry area, and ensure all clothing/protective equipment is dry.
■ Maintain as large a distance as possible between the pacemaker and any current-carrying component (arc/cables/power source) – arms-length/60cm is often recommended.
■ Keep the welding cables (current and return) close together and as far away from you as possible.
■ Keep the welding power source at as large a distance as possible.
■ Ensure that cables are not coiled around the welder (eg over a shoulder, around the arm or laid across the lap) or coiled at their feet.
■ Connect the current return as close to the welding point as possible.
■ Wait several seconds between attempts when struggling to start an arc – do not rapidly “tap” the arc.
■ Work using the ‘buddy’ system with a colleague who understands these guidelines and has an ‘in case of emergency’ plan.
■ Immediately stop welding and step away from the area if you start feeling lightheaded, dizzy, or you believe your pacemaker is performing incorrectly.
■ Minimise the risk of dropping the torch onto the workpiece where possible, or use a trigger system that lowers the risk of inadvertent arcing in case of shock.

Maintain distance

It is not possible to shield the welder from the magnetic field generated by welding (e.g. there are no suitable aprons or overalls which can prevent the magnetic field from reaching the pacemaker). However, the field decreases quickly with distance.
As such, while manual welding has a significant risk factor, robotic or mechanised welding, in which the operator maintains a sufficient distance (>2m), should not pose a risk.
If the pacemaker user has any doubts about his or her working environment, they should take this up with the hospital that fitted the unit. The hospital could be asked to fit the user with a Holter monitor to confirm if there is a problem. This is a form of portable ECG machine worn by the user for a period of 24hrs which monitors and records the functioning of the heart. This would enable any effect of the environment on the operation of the pacemaker to be detected.

This article is produced with kind permission from TWI and the author. For information visit www.twi-global.com