Distinction between operator and patient in medical standards, concept of MOP

Medical AC/DC Power Adapters — This explains the concept of medical standards MOP in desktop & wall-mount types and medical power supplies, along with each category.

Concept of MOP and Categories of Protection Methods

Medical AC/DC Power Adapters — Desktop & Wall-Mount and switching power supplies are compliant with evolving medical standard 60601. When the standard was updated to its third edition, the concept of differentiating between patients and operators was introduced and gained attention.

This led to the introduction of the concept known as MOP (Means of Protection), which is categorized into two groups: MOPP (Means of Patient Protection) for patient protection, and MOOP (Means Of Operator Protection) from the operator's perspective.

Manufacturers of medical equipment have the responsibility to determine whether to implement MOPP or MOOP, considering the possibility that patients may come into contact with the product.

In any case, under normal operating conditions, the insulation between the primary and secondary circuits must include at least two MOPs, and the insulation between the primary circuit and protective earth must include at least one MOP.

What is MOP?

As briefly mentioned above, MOP refers to measures taken to reduce the risk of electric shock-related fatalities. All medical devices are required to have at least one MOP.

However, the third edition of 60601 distinguishes between devices that operators are more likely to handle and those that may come into contact with patients, imposing stricter requirements for patients. This is based on the assumption that operators are generally healthy individuals and thus may be less affected by electric shock. Also, since they are trained in the proper use of the product, the risk of electric shock is presumed to be small if the device is used correctly.

The medical standard also stipulates that in certain conditions, two or more MOPs are required as a safety measure in case one MOP fails. Commonly utilized MOPs include protective grounding, safe insulating materials, creepage distance, clearance, and protective impedance. Most current medical-grade power supplies use a combination of these methods.

What is MOOP?

As mentioned above, MOOP refers to operator protection and is applicable only when the patient never comes into contact with the device. For example, in vitro diagnostic devices used only in medical labs, such as centrifuges, often require only MOOP. Equipment compliant with IEC/EN 60950—typically devices connected to power outlets—generally meets MOOP requirements.

* Note that IIEC/EN60950 has been replaced by IEC62368, and patient protection methods are now referred to as "safeguards."

What is MOPP?

Devices used in situations where there is a risk that patients may come into contact with them require one or more MOPPs. This includes equipment like hospital stand lights, beds, ultrasound diagnostic devices, MRIs, dialysis machines, and more. According to healthcare standards, the highest level of protection requires at least two MOPPs.

In the case of power supplies, when two are required by medical standards but the switching power supply only provides one MOPP, using a DC-DC converter to reconfigure the system can create an additional insulation layer and thereby add another MOP. Although this method is not very efficient and can be costly, it is a straightforward and common approach to meeting compliance requirements.

Using two MOPPs as a highly safe protection method ensures that if one fails, the second provides backup protection, reducing risk to the patient. MOPP must be distinguished from MOOP. Device manufacturers must perform a risk assessment based on EN 60601-1 regulations, specify MOP, and define both MOOP and MOPP accordingly.

What’s the Difference Between MOOP and MOPP?

The main difference between MOOP and MOPP lies in the required insulation distances, typically shown as follows in the medical power supply industry:

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 seen above, the required protection levels differ. Unifive's medical power supplies are designed based on 2xMOPP—the strictest level defined in medical standards—and also comply with 2xMOOP operator protection requirements.