Investigation of functional safety requirements in active medical devices

If functions with risk of danger in active medical devices are prevented by using programmable electrical medical systems, faults in these control systems must not lead to an unacceptable risk. IEC 60601-1 and particular device standards define the requirements for the development and implementation of programmable electrical medical systems, requiring that the safety functions of the device shall be carried out automatically by the protective systems. In addition, 2017/745 numbered Medical Device Regulation requires that the programmable electronic systems in medical devices shall be designed to ensure continuity, reliability and performance. This thesis examines how the reliability requirements of Medical Device Regulations and standards are explained. It has been determined that the reliability criteria required for programmable control systems in medical device standards match the functional safety standards. However, it has been determined that the safety integrity level (SIL) of the control system and the techniques to be used in the design of the medical device standards do not explained. In this respect, the reliability of active medical devices will be ensured by using functional safety standards used in all safety critical applications including automotive industry, process safety and nuclear power plants. For functional safety of the hardware, the systematic errors and random hardware failures are examined and the method of reliability calculation is explained. For the architectural structures 1oo1, 1oo2, 2oo2, 1oo2D and 2oo3, the failure probabilities obtained using the reliability block diagram method according to IEC 61508. Then, it is explained how to obtain the failure rates to be used in SIL calculation by using failure modes and failure rates of components for random hardware failures according to Failure Mode and Effects Analysis(FMEA). A program was developed in MATLAB to calculate the failure probability of each subsystem according to hardware architecture and failure probabilities was calculated. Then, using the calculated failure probabilities, it was shown how to increase the reliability level of a sample control system.