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

This explains the concept of medical standards MOP in medical AC/DC Power Adapters — Desktop & Wall-Mount and medical power supplies, as well as each category.

Categories and Concepts of MOP and Protection Methods

Medical standard 60601 for AC adapters for medical devices and medical switching power supplies has been updated over time. When transitioning to the third edition, the concept of distinguishing between patients and operators was introduced and gained attention.

This led to the emergence of the concept of MOP (Means of Protection), which is categorized into two groups: MOPP (Means of Patient Protection), protection means from the patient’s perspective, and MOOP (Means of Operator Protection), protection means from the operator’s perspective.

Manufacturers of medical devices are responsible for determining whether to adopt either MOPP or MOOP, considering the possibility that a patient may come into contact with the product.

In any case, under normal operating conditions, insulation between primary and secondary circuits requires at least two MOPs, and insulation between primary circuit and protective grounding requires at least one MOP.

What is MOP?

As mentioned above, MOP is intended to reduce the risk of fatal electric shock, and at least one protective measure (MOP) is required for medical devices.

However, the third edition of the 60601 standard distinguishes between equipment likely touched only by operators and that which may be touched by patients, with stricter requirements for the latter. The reasoning is that operators are generally healthy individuals and therefore less likely to be harmed by electric shock. Additionally, device operators are trained to handle products properly, making electric shocks less likely.

The medical standard further stipulates that in certain situations, more than two MOPs are required as a fail-safe measure in case one MOP fails. Common MOP methods include protective grounding, safe insulation materials, creepage distances, clearance, and other protective impedance. Most current medical power supplies use a combination of these methods.

What is MOOP?

As noted above, MOOP refers to protection for operators and applies only in situations where patients do not come into contact with the equipment. For example, in vitro diagnostic devices used only in medical laboratories, such as centrifuges, typically fall into the category where only MOOP is required. Devices complying with IEC/EN 60950, i.e., those powered via standard wall outlets, generally meet MOOP requirements.

*Note: The current standard IEC/EN 60950 has been replaced by IEC 62368, and the term “safeguard” is now used for patient protection measures.

What is MOPP?

For equipment used in medical settings that poses a risk of patient contact, at least one MOPP is required. This includes hospital floor lamps, beds, ultrasound diagnostic machines, MRI scanners, dialysis systems, and more. The highest level of protection defined by medical standards mandates two MOPPs.

For power supplies, if a switching power supply has one MOPP but two are required, incorporating a DC-DC converter in the system can establish an additional insulation layer, thus adding another MOP. While this method may be inefficient and cost-ineffective, it is a simple and quick approach to ensuring product compliance with this level of medical standard, making it a common industry practice.

Adding two MOPPs as a highly secure protective measure ensures that even if one fails, the second provides a backup, mitigating risk to patients. It is essential to distinguish MOPP from MOOP. Medical device manufacturers must assess risk based on EN 60601-1 to determine necessary MOPs and ensure proper configuration of MOOP and MOPP.

What is the difference between MOOP and MOPP?

The major difference between MOOP and MOPP lies in insulation distances. In the medical power supply industry, they are typically represented as follows:

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

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

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

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

*2X indicates double insulation

From the above levels, you can see the differences. Unifive's medical power supplies are designed based on 2xMOPP, the most stringent requirement defined by medical standards, and are also compliant with 2xMOOP for operator protection.