Cochlear Fluids Simulator

Details of Revisions (most recent first)

1) The units for RW permeability in the RW application option have been corrected.In previous version of the simulator the units are incorrect. The units are now stated as x 10-3 cm/s (or x 10-5 m/s).

2) A new installation program has been used, which should make installation easier on more recent versions of Windows (XP). This installation must either be performed with Internet Explorer, or the .msi file should be saved to a directory and executed as a program.

1) Ability to start simulator without clearing the data buffers, so that a preceeding calculation can be continued. Enabled via a checkbox on the front page.

2) Ability to store a calculated concentration-distance profile in a buffer, and to recall that buffer for subsequent calculations (see Distance page)

3) Incorporation of simulation of a micro-dialysis system

4)  Measurement of concentration over a distance "range". The concentration in this range is derived from the total amount of solute in the region, divided by the total volume of the segment

1) "European" bug fixed. Earlier versions of the model would not run properly on PCs set to langages such as French or German. This was due to the different numeric format (comma as decimal delimiter) causing some variables not to be initialized properly. Numeric conversions are now compatible with all country formats.

2) Simulation of the CHINCHILLA cochlea is now possible, based on area and round window data generated by one of our our students, Arthur Wood.

3) Simulation of the aspiration of a fluid sample is now incorporated. The rate of withdrawal is variable and induced perilymphatic flows are accounted for.

4) Additional endolymhatic, perilymphatic and middle ear measurements are included, all of which can be graphed and data transferred to other applications (via the clipboard).

Program recompiled in Microsoft Visual Basic Version 6.0 (previously Visual Basic v 4.0)
no other changes

(Many enhancements of this version)
1) For simulation of solute delivery to the round window membrane there are now more variables.

1a) For the guinea pig, an accurate measure of round window area and its precise relationship to scala tympani (derived from MR images, presented by Ghiz et al., ARO meeting 2000) have been incorporated.
1b) The volume of solution injected into the middle ear can be specified. If a finite volume is injected, the middle ear concentration will fall as solute diffuses into the cochlea.
1c) Clearance of solute from the middle ear can be specified

2) The diffusion coefficient, time and current status of the simulator are now shown on a top bar which is visible from all screens.
3) The profile of concentration versus distance along the cochlea (on the Distance page) can now be saved to the clipboard, allowing the data to be transferred to other programs (spreadsheet, graphics, etc).
4) Current calculation parameters can be saved to the clipboard by a button on the "Setup" page, allowing them to be stored with other model output (e.g. paste into editor program and print out).
5) Concentration scaling of all traces is now performed by a single set of buttons on the "Distance"page.
6) Additional monitoring options are available in addition to specific cochlear locations (on the "Recordings" page). The output can now display a total "SV perilymph" concentration, or endolymph, ST perilymph, Total perilymph (ST+SV) and SV perilymph including the perilymphatic portion of the vestibule (volume defined on the "Communications" page).
7) A length and area can be given to approximate the vestibular perilymph. Note: These data could be incorporated into the SV profile if accurate values were available. Presently, such data are not available.
8) An "experimental" additional compartment, parallel to and in communication with ST, has been incorporated. In vivo measures have suggested that calculations based just on the scala volumes appear to underestimate the total volume available. This is because extracellular spaces in contact with the fluids, such as the spiral ligament, organ of Corti and extracellular spaces of the spiral ganglion and auditory nerve represent additional compartments that solutes can enter. This is not a significant problem for basal turn measures, where the scala are large relative to the these other spaces, but in apical turns this appears to be a significant factor which must be considered. At present these spaces are modeled as a compartment of specified area, which has the same clearance properties as ST. Solute will diffuse between ST and this compartment according to the prevailing concentration gradient.

1) An improvement has been made in fluid flow algorithm, used for simulation of perfusions and perilymph leaks. In earlier versions of the program, the use of high flow rates through small diameter scalae (over 5 ul/min through the guinea pig cochlea) could give erroneous results. The new algorithm is now accurate with all flow rates anyone is ever likely to use.

1) Round window solute entry modification: In the initial release, the round window was simulated as at 90 degrees to the cochlear base. For some species (including the gerbil and mouse) this presented problems as the scala tympani narrows towards the base, with the round window really lying at an angle to the scala. To better approximate the anatomical situation, an additional parameter has been added for the round window, which is the distance it entends along scala tympani (in mm). This can be set from 0 to 10 mm. Solute entry is assigned to multiple elements of scala tympani according to the corresponding membrane area for that element. This is performed by cutting the circle representing the round window into area segments with a series of parallel cuts. Please note that as yet we do not have numeric data regarding the distance the RW extends along scala tympani in each species. We are working on this and hope to make it available later this year.

2) Display clearing: The main display is now cleared when the modeled species is changed

3) A bug in handling "Pause Times" has been fixed. Previously, a specified pause time was erroneously cleared when calculations were resumed after a specified pause.

Initial Release V 1.0, January 1, 1999