1 Hazards of Medical Electrical Equipment
Medical electrical equipment can present a range of hazards to the patient, the user, or to service personnel. Many such hazards are common to many or all types of medical electrical equipment, whilst others are peculiar to particular categories of equipment.
The hazard presented by electricity exists in all cases where medical electrical equipment is used, and there is therefore both a moral and legal obligation to take measures to minimise the risk. Because there is currently very little official guidance on precisely what measures should be in place in order to achieve this in respect to medical equipment, user organisations have developed procedures based on their own experience and risk assessments. The information in these notes is intended to assist in the development of suitable procedures to this end.
Any test and inspection regime intended to minimise the electrical risks from medical electrical equipment should take into account the likely degree of risk from electrical hazards compared to other hazards of medical equipment. For this reason, various hazards associated with medical electrical equipment are discussed briefly below.
1.1 Mechanical Hazards
All types of medical electrical equipment can present mechanical hazards. These can range from insecure fittings of controls to loose fixings of wheels on equipment trolleys. The former may prevent a piece of life supporting equipment from being operated properly, whilst the latter could cause serious accidents in the clinical environment.
Such hazards may seem too obvious to warrant mentioning, but it is unfortunately all too common for such mundane problems to be overlooked whilst problems of a more technical nature are addressed.
1.2 Risk of fire or explosion
All mains powered electrical equipment can present the risk of fire in the event of certain faults occurring such as internal or external short circuits. In certain environments such fires may cause explosions. Although the use of flammable anaesthetics is not common today, it should be recognised that many of the medical gases currently in use, such oxygen or nitrous oxide, vigorously support combustion. Wherever there is an elevated concentration of such gases, there is an increased risk of fire initiated by electrical faults.
1.3 Absence of Function
Since many pieces of medical electrical equipment are life supporting or monitor vital functions, the absence of function of such a piece of equipment would not be merely inconvenient, but could threaten life.
1.4 Excessive or insufficient output
In order to perform its desired function equipment must deliver its specified output. Too high an output, for example, in the case of surgical diathermy units, would clearly be hazardous. Equally, too low an output would result in inadequate therapy, which in turn may delay patient recovery, cause patient injury or even death. This highlights the importance of correct calibration procedures.
Medical equipment that has been inadequately decontaminated after use may cause infection through the transmission of microorganisms to any person who subsequently comes into contact with it. Clearly, patients, nursing staff and service personnel are potentially at risk here.
Misuse of equipment is one of the most common causes of adverse incidents involving medical devices. Such misuse may be a result of inadequate user training or of poor user instructions.
1.7 Risk of exposure to spurious electric currents
All electrical equipment has the potential to expose people to the risk of spurious electric currents. In the case of medical electrical equipment, the risk is potentially greater since patients are intentionally connected to such equipment and may not benefit from the same natural protection factors that apply to people in other circumstances. Whilst all of the hazards listed are important, the prevention of many of them require methods peculiar to the particular type of equipment under consideration. For example, in order to avoid the risk of excessive output of surgical diathermy units, knowledge of radio frequency power measurement techniques is required. However, the electrical hazards are common to all types of medical electrical equipment and can minimised by the use of safety testing and inspection regimes which can be applied to all types of medical electrical equipment.