[00:00:42]
>> You know that your research mall. You heard that one right. I was on for you just say this right here where you are side by side with scissors here or less right on or do the test the models were fix that is what materials testing machine a preloaded a five hundred fifty Newtons was applied and held for two minutes when the the set up was allowed to rest for three minutes.

[00:03:09]
After that the five hundred test load was applied was tested corresponds to the upper body weight of a seventy kilogram person the test load was also held for two minutes and at the end of the two minute load pressure data was captured by the affixed F.S.A. sensors three trials were taken per condition and there were fourteen conditions seven questions and two models.

[00:03:30]
Test retest comparison was used to determine our variables. We originally tried to use RAW magnitude variables but found that those were not repeatable. So we moved to ratios for this data which is all data taken with no map present the Friday to forty five is used as a reference to create the ratio.

[00:03:50]
The total negative one to one ratio is that magnitude variable that I'll be discussing today and it's calculated by adding together the pressure found at the three most inferior sites of them on the model. And element as measured by the equality of. The pressure measured at the different points of interest ideal envelopment would result in even pressure across the entire surface of the model.

[00:04:12]
Both parity and the coefficient of variation are measures of the equality at different points of interest. Parity. Parity uses both the points that are once in a meter superior to the I.C.. And the cooperation of variation is the variable that was calculated using the second sensor configuration with all five sensors for both these variables closer to zero indicates that the points of interest are more equal to each other and therefore that the envelopment is better.

[00:04:42]
So for results for magnitude. We found a significant difference between the models for five of the questions and overall. Overall the magnitude was higher when measured using the Dell model. However there was a significant drop in magnitude with both the action and the segmented H.R. forty five question.

[00:05:03]
Envelopment. Was a little bit clearer as there was a greater involvement with the Dell model for five questions and overall and the only questions. There were not there around that went the opposite direction there were only two questions that had no effect between the models. With this lower parity.

[00:05:21]
This means that the pressure of the two sites is more equal when using the gel model than when using the original model as I mentioned both the J. D. from the star so no difference between the models that you can see here there parity is very low meaning that their involvement was very good.

[00:05:35]
With both models. The difference in envelopment you see between the model indicates that the shape of the inventor question. Interface is different between the models. So with a rigid model the wheelchair cushion has to conform to its surface. However with a gel model both the wheel chair cushion and the model can conform.

[00:05:55]
So when the gel model's able to come form to the surface of the cushion the better envelopment result. As a mission the coalition a very. Ation is another measure of envelopment that we used this was taken with this second sensor can figure action and only done with three questions.

[00:06:12]
Overall again with the gel model the envelopment was the in the melon was better with the gel model. However again that day deep cushion. Was slightly different this time having a significantly worse envelopment with the gel model and this could possibly be because the top layer of the gel of the J. deep cushion is a broader filled with a very displaced little discus fluid.

[00:06:35]
So maybe that the displacement of the gel model does not come into play because the cushion itself is so displaced of all. So for all variables there is a significantly statistically significant interaction between the model and the question and this means that the difference between the models is different depending on the question being tested.

[00:06:54]
When loaded the cushions to form and how they deformed depends on what material they're made of so you can see in these pictures from Christians compressed air Broadhurst collapse and general displaces. Additionally as I mentioned the gel model also deformed under load. This defamation is influenced by the stiffness of the question and the load applied.

[00:07:16]
To complicate things. This information is not necessarily consistent every time you load the model and the question the film could compress differently their particular plot could collapse differently and the Dell could displace differently. The result of this inconsistency and defamation is that the pressure measured is quite a volatile effect in the repeatability of the results.

[00:07:38]
Additionally the model that is used. Effects how the question performance is measured what I mean is that when using the rigid model for example some Christians had a higher magnitude that with the Dell model. Meaning that they were not worse than the other questions. However this could switch when using the Dell model they may or may appear to be better than the other person and what I mean is that.

[00:08:04]
The test methods affect the test results. So in conclusion different model materials were seen to affect pressure magnitude and envelopment and there was an influence in the Christian construction so significant because standardized tests use models to measure Christian performance and they need to be repeatable and valid Intuitively it seems like the gel model would be better.

[00:08:27]
Representative of a human subject. However as I mentioned the inconsistent loading that you see with the gel model and the creation can result in pressure relativity which could bring down the repeatability to a level that is in the unacceptable for standardized tests. Additionally human tissue consistency varies greatly people can have different tissue consistency and different tissue a mouse.

[00:08:54]
Therefore the consistency of a rigid model may be preferred to best represent all of these different human consistencies. The session be repeated using human subjects to see which model is most most behaves like a human. However it's not very transferable to a human and that the pressure sensors were taped to the brother models which is not very feasible using humans and what's really the difficulty is to visit their configuration the sensors were placed according to their vertical relationship to the I.C. which could not be done with a human subject.

[00:09:31]
The pressure sensors that are able to be used for human subjects are the thin pressure sensing matter that I discussed early in the presentation. However the other part of the subject found that the addition of those pressure sensing math into the interface can also change the result of pressure reading to you and envelopment.

[00:09:48]
So in conclusion when developing standardized test methods the effects of model design center configuration and their influences with the question construction should be considered. Her you know which. That is a very tough question because as I mentioned. Human Tissue is just so so different across people so they are sitting specialists who this is their job to select wheelchair cushions and and to put together wheelchairs that are most appropriate for the people so they take into consideration a variety of factors air questions such as the star.

[00:10:41]
Are very good at the shipping pressure but some people have trouble using them because they may need to push on to their cushion to transfer so they may not be able to use them or they may have hyper sensitivity to the fingers touching them. The different the day cushion is also does very well but again there are problems with with the gel broader and different factors that may be very individualized So I think that for question selection really should be done by a seeding specialist using a variety of tools.

[00:11:11]
One of which may be pressure mapping. I think that the results. Maybe should provide them more with some insight into how they should make their decision. I don't think that these results are really should be used to say this question is better than the other one because it's really more of a relative measure just for that just for this instance.

[00:11:46]
So I'm not sure if these results would be repeatable. And to say this question behaves the best. I think that it is insightful for them to know that they should consider. Especially with the other part of the study the pressure sensing that how they are affecting the interface by applying by using this tool.

[00:12:05]
And also anything else that they read in that says that this question is the best if you can consider how those tests were done and and whether or not those results are actually valid. Yes. SARAH That's a very good question and a limitation of this study. In that the pressure sensors that we used only measure normal pressure and they did not take into consideration the sheer force and sheer force has been shown to significantly affect the incidence of skin breakdown.

[00:12:57]
So when sheer force is present skin breakdown requires much lower pressure to create and ulceration. And in this study. Like I said we're not we're leaving out here for us this is strictly a normal pressure study. So one way the another thing that could be done is to use try actual sensors to see how this year forces comes into play in the situation.

[00:13:30]
O O O O O O O O O O O O O O O. They are the pressure sensing that they are all flat to begin with but some of them incorporate some stretch with the idea that they would be able to more easily contour However with that study we did find that all of the mats had a significant result on both pressure envelopment and in magnitude.

[00:14:56]
Yes I have seen that I read about that in the literature where they've done that with residual limbs to try to create to try to calibrate the sensors actually on a on a limb. We have not. We've talked about doing that in our lab but we have not yet done it.

[00:15:14]
We haven't tried it and also there are a lot of there are a lot of things that go into that as far as how to actually apply the pressure and how you can be assured that the pressure is evenly distributed across the model. So yeah I think you really have to get into some sort of air chamber.

[00:15:30]
So that you really know that you're applying a uniform pressure because if you just have a negative in your applying a force pressure isn't going to be distributed across the surface everywhere and you wouldn't be able to exactly know what pressure you are applying to the sensor to be able to calibrate them to it.

[00:15:51]
OK Well turn it over to Ron the. Thank you.