On the distinction between operator and patient in medical standards, and the concept of MOP

This explains the concept of MOP in medical standards for medical AC/DC Power Adapter and medical power supplies, as well as each category.

About the Concept of MOP and Categories of Protective Measures

The medical standard 60601 for AC/DC Power Adapter and medical switching power supplies used in medical devices has been updated over time. When it was revised to the 3rd edition, the concept of distinguishing between patients and operators was introduced and attracted attention.

As a result, the concept of MOP (Means of Protection) was established. Within this framework, two groups were defined: MOPP (Means of Patient Protection), which refers to protective measures for patients, and MOOP (Means of Operator Protection), which refers to protective measures for operators. These categories distinguish protection from the patient’s perspective and from the operator’s perspective.

Manufacturers of medical devices are responsible for considering the possibility that a patient may come into contact with the Products and deciding whether to adopt Means of Patient Protection (MOPP) or Means of Operator Protection (MOOP).

In all cases, under normal conditions, at least two MOPs are required for insulation between the primary and secondary circuits, and at least one MOP is required for insulation between the primary circuit and protective earth.

What is MOP?

As mentioned above, MOP is a measure intended to reduce the risk of fatal electric shock, and medical devices are required to have at least one Means of Protection (MOP).

However, the 3rd edition of 60601 distinguishes between equipment that is likely to be touched only by operators and equipment that may be touched by patients, imposing stricter requirements for patient protection. This is based on the idea that operators are generally healthy individuals, so even if they experience electric shock, the impact is likely to be less severe than for patients. In addition, equipment operators are trained to properly handle the Products, and if handled correctly, the likelihood of electric shock is considered low.

The medical standard also stipulates that in certain situations, two or more MOPs are required. This serves as a safety measure in case one MOP fails. Commonly used MOPs include protective earth, safe insulation materials, creepage distances, clearances, and other protective impedances. Most modern medical power supplies use a combination of these methods.

What is MOOP?

As described above, MOOP refers to Means of Operator Protection and applies only in situations where patients do not come into contact with the equipment. For example, many in-vitro diagnostic devices used exclusively in medical laboratories, such as centrifuges, are classified as requiring only MOOP. Equipment compliant with IEC/EN 60950, that is, devices connected to a power outlet, generally meets MOOP requirements.

*Currently, IEC/EN 60950 has been replaced by IEC 62368, and Means of Patient Protection are referred to as safeguards.

What is MOPP?

Equipment used in medical settings where there is a risk that patients may come into contact with it must have at least one Means of Patient Protection (MOPP). This includes hospital stand lighting, beds, ultrasound diagnostic equipment, MRI systems, dialysis machines, and more. For the highest level of protection defined by medical standards, at least two MOPPs are required.

In the case of power supplies, if a switching power supply provides one MOPP but two are required under medical standards, adding a DC-DC converter and redesigning the system configuration can provide an additional insulation layer, thereby adding another MOP. Although this method may be inefficient and result in poor cost performance, it is a simple and quick way to add an MOP to ensure the Products complies with the required level. Therefore, this approach is widely used.

In cases where two MOPPs are implemented as a highly reliable protective measure, even if one fails, the second serves as backup protection, thereby reducing risk to the patient. MOPP must be distinguished from operator protection measures. Equipment manufacturers must conduct risk assessments in accordance with EN 60601-1 regulations to determine the required MOPs and appropriately define MOOP and MOPP.

What is the difference between MOOP and MOPP?

The main difference between MOOP and MOPP lies in insulation distance. In the medical power supply industry, they are generally expressed as follows:

1xMOOP: Withstand voltage 1500VAC, creepage and clearance 2.5mm/2mm

2xMOOP: Withstand voltage 3000VAC, creepage and clearance 5mm/4mm

1xMOPP: Withstand voltage 1500VAC, creepage and clearance 4mm/2.5mm

2xMOPP: Withstand voltage 4000VAC, creepage and clearance 8mm/5mm

*2X indicates double insulation

As shown above, there are differences depending on the level. Unifive medical power supplies are designed based on 2xMOPP, the strictest standard defined by medical regulations for Means of Patient Protection, and also comply with 2xMOOP, Means of Operator Protection.