Effect of Underwater Insertion on Intracochlear Pressure

Abstract

Background: The importance of intracochlear pressure during cochlear electrode insertion for the preservation of residual hearing has been widely discussed. Various aspects of pre-insertional, intra-insertional, and post-insertional relevant conditions affect intracochlear pressure. The fluid situation at the round window during electrode insertion has been shown to be an influential factor.Aims/Objectives: The aim of the study was to compare various insertion techniques in terms of the fluid situation at the round window.Material and Methods: We performed insertion of cochlear implant electrodes in a curled artificial cochlear model. We placed and fixed the pressure sensor at the tip of the cochlea. In parallel to the insertions, we evaluated the maximum amplitude of intracochlear pressure under four different fluid conditions at the round window: (1) hyaluronic acid; (2) moisturized electrode, dry middle ear; (3) middle ear filled with fluid (underwater); and (4) moisturized electrode, wet middle ear, indirectly inserted.Results: We observed that the insertional intracochlear pressure is dependent on the fluid situation in front of the round window. The lowest amplitude changes were observed for the moisturized electrode indirectly inserted in a wet middle ear (0.13 mmHg ± 0.07), and the highest values were observed for insertion through hyaluronic acid in front of the round window (0.64 mmHg ± 0.31).Conclusions: The fluid state in front of the round window influences the intracochlear pressure value during cochlear implant electrode insertion in our model. Indirect insertion of a moisturized electrode through a wet middle ear experimentally generated the lowest pressure values. Hyaluronic acid in front of the round window leads to high intracochlear pressure in our non-validated artificial model.

The effect of surgeon experience and insertion speed on intracochlear pressures during in-vitro cochlear implantation

“…The authors hypothesized that that moisturizing the electrode may counteract naturally hydrophilic properties of a silicone electrode. Some studies have found a positive effect from underwater insertion (Riemann et al, 2020;Stuermer et al, 2018), further supporting this concept, however the significance of this variable has been questioned (Stuermer et al, 2018) and our study did not demonstrate any positive effect from this intervention. Furthermore, the method of moistening the electrode in our study was inconsistent: some participants dipped the electrode in water, while others poured water over the electrode.…”

Impact of Insertion Speed, Depth, and Robotic Assistance on Cochlear Implant Insertion Forces and Intracochlear Pressure: A Scoping Review

“… Impact of robotic insertion on pressure measurements in artificial cochlea models [ 19 , 20 , 22 , 30 , 31 , 34 , 35 , 36 ]. Unweighted two-sample t -tests were used for ( I , III , IV ), with significant differences found in mean pressure measurements (box charts not weighted, p < 0.001).…”

“…The distribution of these instances may indicate potential areas for improvement in the RW approach to minimize the occurrence of insertion trauma. [19,20,22,30,31,[34][35][36]. Unweighted two-sample t-tests were used for (I,III,IV), with significant differences found in mean pressure measurements (box charts not weighted, p < 0.001).…”

“…To investigate factors such as insertion speed, insertion depth, electrode design, surgical approach and angular depth, and the use of semi-automated or fully automated insertion techniques which influence insertion force (IF) and intracochlear pressure (IP) changes, researchers have employed physical artificial models (e.g., scala tympani or combined-scalae cochlea models fabricated from plastic or similar materials) [ 11 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 ] as well as computational simulations [ 24 ] in their studies. These models provide a controlled environment for observing and measuring the IFs and transient IP changes that arise during CI insertion.…”