Acoustic to Electric Pitch Comparisons in Cochlear Implant Subjects with Residual Hearing

The aim of this study was to assess the frequency-position function resulting from electric stimulation of electrodes in cochlear implant subjects with significant residual hearing in their nonimplanted ear. Six cochlear implant users compared the pitch of the auditory sensation produced by stimulation of an intracochlear electrode to the pitch of acoustic pure tones presented to their contralateral nonimplanted ear. Subjects were implanted with different Clarion® electrode arrays, designed to lie close to the inner wall of the cochlea. High-resolution radiographs were used to determine the electrode positions in the cochlea. Four out of six subjects presented electrode insertions deeper than 450°. We used a two-interval (one acoustic, one electric), two-alternative forced choice protocol (2I-2AFC), asking the subject to indicate which stimulus sounded the highest in pitch. Pure tones were used as acoustic stimuli. Electric stimuli consisted of trains of biphasic pulses presented at relatively high rates [higher than 700 pulses per second (pps)]. First, all electric stimuli were balanced in loudness across electrodes. Second, acoustic pure tones, chosen to approximate roughly the pitch sensation produced by each electrode, were balanced in loudness to electric stimuli. When electrode insertion lengths were used to describe electrode positions, the pitch sensations produced by electric stimulation were found to be more than two octaves lower than predicted by Greenwood's frequency-position function. When insertion angles were used to describe electrode positions, the pitch sensations were found about one octave lower than the frequency-position function of a normal ear. The difference found between both descriptions is because of the fact that these electrode arrays were designed to lie close to the modiolus. As a consequence, the site of excitation produced at the level of the organ of Corti corresponds to a longer length than the electrode insertion length, which is used in Greenwood's function. Although exact measurements of the round window position as well as the length of the cochlea could explain the remaining one octave difference found when insertion angles were used, physiological phenomena (e.g., stimulation of the spiral ganglion cells) could also create this difference. From these data, analysis filters could be determined in sound coding strategies to match the pitch percepts elicited by electrode stimulation. This step might be of main importance for music perception and for the fitting of bilateral cochlear implant

Elimination of fluconazole during continuous renal replacement therapy. An in vitro assessment

International audienceIntroduction:Continuous renal replacement therapy (CRRT) efficiently eliminates fluconazole. However, the routes of elimination were not clarified. Adsorption of fluconazole by filters is a pending question. We studied the elimination of fluconazole in a model mimicking a session of CRRT in humans using the NeckEpur® model. Two filters were studied.Methods:The AV1000®-polysulfone filter with the Multifiltrate Pro. Fresenius and the ST150®-polyacrylonitrile filter with the Prismaflex. Baxter-Gambro were studied. Continuous filtration used a flowrate of 2.5 L/h in post-dilution only. Session were made in duplicate. Routes of elimination were assessed using the NeckEpur® model.Results:The mean measured initial fluconazole concentration (mean ± SD) for the four sessions in the central compartment (CC) was 14.9 ± 0.2 mg/L. The amount eliminated from the CC at the end of 6 h-session at a 2.5 L/h filtration flowrate for the AV1000®-polysulfone and the ST150®-polyacrylonitrile filters were 90%–93% and 96%–94%, respectively; the clearances from the central compartment (CC) were 2.5–2.6 and 2.4–2.3 L/h, respectively. The means of the instantaneous sieving coefficient were 0.94%–0.91% and 0.99%–0.91%, respectively. The percentages of the amount eliminated from the CC by filtration/adsorption were 100/0%–95/5% and 100/0%–100/0%, respectively.Conclusion:Neither the ST150®-polyacrylonitrile nor the AV1000®-polysulfone filters result in any significant adsorption of fluconazole

Short-Term Assessment of Obstructive Sleep Apnea Syndrome Remission Rate after Sleeve Gastrectomy: a Cohort Study

International audienceBackgroundSevere obesity is associated with a high prevalence of moderate-to-severe obstructive sleep apnea syndrome (OSA). Bariatric surgery has been shown to effectively reduce excess weight and comorbidities.MethodsWe evaluated the remission rate of moderate-to-severe OSA (apnea-hypopnea index (AHI)>= 15) following sleeve gastrectomy. We performed a single-center retrospective chart review of all patients who underwent preoperative polysomnography (PSG) or polygraphy before primary sleeve gastrectomy. Patients with moderate-to-severe OSA treated by continuous positive airway pressure (CPAP) also underwent postoperative PSG. Bivariate analysis was performed to evaluate the criteria associated with remission of moderate-to-severe OSA.ResultsFrom 2013 to 2018, 39 of 162 patients (24.1%) scheduled for sleeve gastrectomy (SG) presented moderate-to-severe OSA requiring CPAP. Postoperative PSG was performed in 36 patients a mean of 9.96.1 months after SG. Mean BMI decreased from 47.4 +/- 8.4 to 36.3 +/- 7.1 kg/m(2) (p<0.001), and all patients reported clinical improvement of OSA symptoms. A remission of moderate-to-severe OSA was observed in 72.2% of patients with a mean decrease of AHI from 45.8 events/h to 11.3 events/h (p<0.001). Postoperative neck circumference was the only factor associated with OSA remission.Conclusion SG is associated with a rapid improvement of moderate-to-severe OSA partially as a result of a reduction of neck circumference. However, the absence of correlation with excess weight loss suggests that other weight-independent factors may also be involved