Effect of changing pulse rate on profile parameters of perceptual thresholds and loudness comfort levels and relation to ECAP thresholds in recipients of the Nucleus CI24RE device

Abstract

The Nucleus CI24RE ‘Freedom' device offers higher stimulation rates and lower noise levels in action potential measurements (ECAPs) than previous devices. A study including ten European implant teams showed that the effect of changes in rate from 250 to 3500 pulses per second on tilt and curvature of the T and C profiles is insignificant. When changing rate one may change the levels at all electrodes by the same amount. Using an automated procedure ECAPs could be measured quickly and reliably at a noise level of only 1 microV, this did not result in improved correlations between the tilt and curvature parameters of the ECAP profiles and those of the T and C profiles. Average C levels appear to differ markedly among implant centers; a better assessment protocol is required. When increasing stimulus rate one should take into account that this requires higher pulse charges per second and more power consumption.

Population-Based Prediction of Fitting Levels for Individual Cochlear Implant Recipients

“…This is obviously less than the 20 dB DR obtained when T-levels are set at 10% of the M-levels, which is the default setting in SoundWave, the manufacturer's fitting software. The 9-to 14-dB electrical DR is in line with the data reported by Wesarg et al [2010] for Nucleus cochlear implant recipients. In previous studies, even lower DRs of around 8 dB were described [Pfingst and Xu, 2005].…”

“…Smoorenburg [2007] reported increases in T-and M-levels for both adults and children. In contrast to Smoorenburg [2007], Walravens et al [2006], Hughes et al [2001] and Wesarg et al [2010] showed stable T-levels in adults after initial fitting. In children, Hughes et al [2001] showed that T-and M-levels continued to increase months after implantation and first fitting.…”

“…It is well known that threshold and maximum levels vary considerably between recipients [Wesarg et al, 2010], and a lot of effort is put into obtaining these levels, mostly using multiple behavioral or objective measurements of the individual recipient. Although the number of cochlear implant recipients has risen dramatically over the years, average mean levels along the array were, to our knowledge, only published for Nucleus (Cochlear, Sydney, N.S.W., Australia) implant recipients [Wesarg et al, 2010], and a widely applicable reference of levels and level profiles is lacking. For the present study, a data set of levels for 151 adult subjects using a CII/HiRes 90K cochlear implant (Advanced Bionics, Sylmar, Calif., USA) has been obtained.…”

“…However, Wesarg et al [2010] and Smoorenburg [2007] analyzed large data sets of T-and M-levels of Nucleus implant recipients to investigate parameters that determine those levels. T-and M-levels are shown to vary considerably, but the dynamic range (DR) was, on average, 50 current levels (SD 20) in Nucleus 22 (bipolar stimulation) [Bento et al, 2005] and Nucleus 24 cochlear implant users (monopolar stimulation) [Wesarg et al, 2010]. This means that the thresholds were about 9 dB lower than the M-levels, i.e., the T-levels were on average at 35% of the M-levels.…”

“…With monopolar stimulation, this across-site variation was much smaller. However, even with monopolar stimulation, numerous researchers report higher thresholds at the basal end of the electrode array [Thai- Van et al, 2001;Smoorenburg et al, 2002;Sainz et al, 2003;Miller et al, 2008;Lai et al, 2009;Botros and Psarros, 2010;Wesarg et al, 2010]. Nowadays, fitting at the basal part of the cochlea receives extra attention as electric acoustic stimulation is emerging [Adunka et al, 2010] and shorter electrodes are being used Lenarz et al, 2009].…”