A medical device is an instrument that includes components,parts,or accessories to diagnose or treat patients.Since the complexity of medical devices has increased in recent years,functional safety and basic safety are required to ensure the overall device safety.Functional safety is part of the overall safety that relates to the equipment under control(EUC)and to the EUC control system that depends on the correct functionality of the electrical/electronic/programmable electronic(E/E/PE)safety-related systems.This study proposes approach methods to functional safety of medical devices for which it is important to correctly identify the safety functions and the safety integrity level(SIL).The relationship between the functional safety and essential performance is identified focusing on the safety function.The essential performance of E/E/PE systems is defined as the safety function of the functional safety.The target SIL of the essential performance is determined according to the potential risk levels,based on the classification rules of medical devices.This approach is applied to the pulse oximeter as a case study.The target SIL for the functionality of the power-failure alarm condition is determined to be SIL1.The target SILs of other functions are determined as SIL2.
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