Medical devices powered by electricity offer life-saving capabilities, yet they also present risks, especially when invasive procedures bypass the body’s natural insulation—the skin. If electric current flows through the body, it can cause severe complications, from heart fibrillation to respiratory paralysis.
The International Electrotechnical Commission (IEC) introduced the IEC 60601 standard in 1977 to address these risks. This standard, now known as IEC 60601-1, establishes safety requirements for electronic devices. Here, we’ll explore the structure of this standard, key definitions, and essential safety features to consider in medical electrical equipment (MEE).
Structure of the IEC 60601 standard series
IEC 60601-1 is divided into two parts:
IEC 60601-1-X: These collateral standards address specific safety and performance concerns, such as electromagnetic interference and x-ray protection.
There are nine such collateral standard currently.
IEC 60601-2-X: In IEC 60601-2-X, the X represents a device-specific collateral standard number. Currently, there are 53 such device-specific collateral standards.
The current version of IEC 60601-1 is edition 3.2. The standard provides the
requirements for electrical safety and covers hazards such as mechanical hazards,
radiation hazards, and hazards due to excessive temperature.
This is the part of the medical device which in normal use is brought in contact or likely to contact the patient.
There are three types of Applied Parts.
Each of these types of Applied Parts can be further classified into ‘Defibrillation Proof”.
The device’s components are touchable but not intended to come in contact with the patient to achieve their function.
An electromedical equipment (The IEC 60601 mentions electro-medical device as medical electrical equipment) that can transfer energy to or from a patient, has no more than one connection power supply, and that its manufacturer intends to be used for diagnosing, treating, or monitoring a patient.
A combination of equipment specified by its manufacturer where at least one of the items is ME Equipment interconnected by a functional connection. A wall socket, however, is not considered a functional connection.
Class of MEE based on levels of protection
MEEs are classified into three classes based on the level of protection.
Class I: Live parts are covered by basic insulation and protective earth. Basic insulation can be achieved by air clearance and/or solid insulation. Protective earth prevents shock if basic insulation fails.
Class II: live parts are covered by two levels of insulation, either reinforced or double,
Class III: Uses an Internal Power Supply, which is a safety extra-low voltage (SELV) circuit, so no additional protection is required
- Normal vs Single Fault Condition
A Normal Condition of a MEE is when all means of protection against hazards are intact.
A Single Fault Condition (SFC) of a MEE is when a single means for reducing a risk is defective or a single abnormal condition is present.
The IEC 60601-1 has listed several examples of Single Faults.
- Interrupted protective earth
- Interrupted supply lead
- Mains voltage on floating applied part
- Mains voltage on signal input/output terminals (SIP/SOP) and enclosure
- Detachment of wire connections, screw terminals, components, etc.
- Locking of moving parts and rotors
- Locking of cooling fans / stop in cooling circulation
- Blocking of ventilation openings
- Blocking of filters
- Simulation of liquid or gas leakage
- Short circuit of one isolation in a double isolation
- Short circuit / open circuit of semi-conductors
- Short circuit / open circuit of capacitors
- Failure of thermostats
- Essential Performance
Essential Performance can be understood by comparing it with Basic Safety. Basic Safety is freedom from unacceptable risk directly caused by physical hazards when the medical device is used under normal condition and single fault condition.
Essential performance is a clinical function, other than related to basic safety, where loss or degradation beyond certain specified limits results in an unacceptable risk.
A function is not considered an essential performance if there is no chance of harm if that function fails.
Some examples of Essential Performance:
- Blood pressure monitor: The ability to accurately measure and display blood pressure levels
- Surgical laser: The ability to deliver precise and controlled energy to tissues
- Cardiac monitor: The ability to accurately measure heart rate and rhythm
- Defibrillator: The ability to deliver electrical shocks within a specified range to treat cardiac arrest
- Oxygen monitor: The ability to monitor oxygen levels and supply oxygen to the patient if their breathing slows down.
- Single Fault Safe
A MEE is called Single Fault Safe if a Single Fault doesn’t lead to unacceptable risk
