A Critical Note to IEC 80601-19 Standard for EEG Wireless Transducers About Trigger Uncertainty in Event-Related Potential Measurement

Event-related potentials (ERPs) are electroencephalographic (EEG) waveforms occurring milliseconds after eliciting environmental stimuli. Measurement of ERP amplitude and latency is widely used in clinical applications concerning neurodegenerative disorders. The amplitude of ERPs is comparable to background noise, thus, the typical procedure for acquiring ERPs consists of averaging over many EEG trials (assuming background noise with zero mean). Therefore, managing the delay uncertainty between stimulus delivery and marker apposition on the EEG trial (trigger delay uncertainty) becomes crucial, in general, and very challenging in the case of wireless transducers. However, also in the last IEC 80601-19 standard for electroencephalographs, trigger delay uncertainty is not mentioned among the listed requirements. In this study, a method is presented to: 1) characterize the trigger delay uncertainty and 2) analyze the propagation of this uncertainty on the ERP amplitude. The method was applied to a wireless device certified for clinical application. Twenty thousand measurements were carried out to characterize the uncertainty of the delay between stimulus delivery and marker apposition on the EEG trial. The delay distribution exhibited a mean value of 447 ms and a standard deviation of 33 ms, not compatible with clinical applications based on ERP latency measurements. In the second step, based on a Monte Carlo simulation, results revealed a propagated uncertainty concerning ERP amplitude compatible with clinical application in Alzheimer’s and Parkinson’s diagnosis (relative percentage uncertainty less than 3% with 95% confidence). The results confirmed the opportunity (especially in the case of wireless electroencephalographs) to update the IEC 80601-19 standard concerning the issue of trigger delay uncertainty management.