ANSI AAMI ISO 14708-3:2017 pdf download – Implants for surgery – Active implantable medical devices
The risk assessment process, performed in accordance with ISO 1 4971 , could result in hazardous situations being identified (see ISO 1 4971 :2007, Figure E.1 ). Since actual risk cannot be observed during testing, it will be necessary to observe the performance of the device to see if any hazardous situations occur. Pass/fail criteria shall be defined prior to testing. Ideally, these criteria can be measurable or observable during testing. If not, the manufacturer shall specify an alternative method for determining that the DUT met the required pass/fail criteria during the test. The use of special hardware or software might be necessary. If the pass/fail acceptance criteria are not met during and after testing, the manufacturer shall substantiate DUT behavioural responses and explain why the overall risk(s) are acceptable (see Table 1 03). In no cases are irreversible changes in performance, outside of specification, allowed.
For all tests, provision shall be made to determine the device’s behavioural responses, preferably during testing. If the operation of the DUT cannot be observed or verified during the test, the manufacturer shall specify an alternative method for determining that the DUT met the required pass/fail criteria during the test. The use of special hardware or software might be necessary.
The low pass filter provides points where the monitoring oscilloscope can be connected to observe DUT output stimulation waveforms during the test. Without this filter, it would be more difficult to separate the injected signal from the DUT output waveform. The lead interface simulates the therapy lead impedance. This may be accomplished by using an actual lead or by circuit model simulation of an actual lead. Both approaches are represented in Figure 1 01 . Test procedure: A test signal generator, monitoring oscilloscopes, and the DUT are connected to the injection network as indicated in Figure 1 01 . DUT output stimulation will need to be selected so that the output waveform can be reasonably monitored throughout the test. If the design of the DUT is equivalent for all electrodes, then only one configuration needs to be tested (see 27.1 02.2). In that case, it is not necessary to exercise several combinations of anodes and cathodes. The frequency range of the applied test signals (V PP ) shall be stepped from 1 6,6 Hz to 80 MHz, pausing to adjust the signal level and to allow enough time for the DUT behavioural response to be observed. Incremental steps are indicated in Table 1 04. Test signal levels (V PP ) are shown in Table 1 05 and shall be applied to Port A (see Figure 1 01 ) according to the frequency ranges and lead lengths shown in Table 1 05. The amplitude of the test signal is defined as the peak-peak amplitude, before modulation, as measured on Port B in Figure 1 01 . At low frequencies and short lead lengths, V PP might be very small. In these cases, the manufacturer may determine the start frequency based on voltages too low to cause a circuit response. For example, at voltages lower than a forward bias diode voltage drop. Rationale shall be provided. The stop frequency is always 80 MHz