PINNED - Cushions

[Burgerman]

WHICH CUSHIONS DO YOU USE AND WHY!
Make a note of history, sores etc, type, size approx, weight, disability and as much useful info as poss.

I have tried many chairs and am suffering pressure sore issues on ischeal tuberosity on one side mostly.
I am 20 stone, 60, and T4 paraplegic.

1. I used a simple polyurethane cheap FOAM cushion for 2 years. 18 wide 20 deep.
I used to sit for 14 hours a day and do pressure lifts every half hour. I then got a minor sore. When first paralised at 37 years old I had a lot of muscle and fat on my backside. A simple foam cushion was OK. No need for a pic.

2. I replaced that with a 18 X 20 Jay2 which I used for 10 years all day long every day and never a problem. It has a very firm outer, that doesent squash at all. And this extends across the front half of the cushion. It makes for superb stability, and is super easy to transfer onto (I transfer sideways from bed etc by lifting with my hands and shuffing across with a wooden polished transfer board. I love that cushion. Actually cushions I have 2 of those and in 10 years only one problem. The GEL fluid sac in the rear half split. White silicone grease everywhere! Strange stuff. That was replaced under warranty.

Downsides? Heavy, and doese not offer quite as much ultimate protection as a ROHO for e.g. A user here suffers from lots of sweating on this cusion. So maybe not as much airflow as some cushions.
Upsides? Easy to transfer. extremely good protection of your sitting bone points where you would get sores. Maybe 9 out of 10. Zero maintainance, and very long lasting. All parts are available seperately along with added extra positioning parts if needed. This is the cushion I recommend to most people in my situation.
PDF sizes and prices http://www.sunrisedice.com/asset-bank/a ... /26847.pdf

There are 2 huge manufactures of the best cushions out there that are the main go to ones. Jay, with many options, and Roho, with many options too.

So this is the JAY (J2) cushion that has been sold for decades because it absolutely works and is easy to use.

A VERY solid base. This can be cut with a small saw. It does not compress unless you drive a car over it.

HARD waterproof foam - it does not absob water.

Fluid /gel pad. This is squishy like grease. Its foam on the front half, gel at the rear. And sits in/on the part above! Obviously...

GEL layer/pad

[Burgerman]

ROHO Quadro Select https://www.activemobility.co.uk/roho-q ... shion-3127

After a decade without sores or problems on the easy to use Jay2 gel cushions, I began to have problems. I started to get off the chair for 1 hour at 5pm daily. And it helped for 5 years more. Since then I have been suffering ischeal tuberosity problems and it started to keep me tied to my bed for most of the time. I get up after it heals and back it comes. Tried around ten different cushions, inc reciprocating air cushions. And home made foam and air ones.

So I stopped using my BM2/3 chairs that I had used in various forms for 15 years and accepted that I had no choice but to get a chair that allowed me to shift weight. With tilt, recline, legs lifted. So bought a brushless invacare Storm4 Explore whichwas returned as its motors were useless. And then a Sunrise quickie Salsa and now a Quickie Q700R. This definitely helps. They are like massive overweight wobbly underpowered monsters compared to my BM2/3 chairs but I dont appear to have a choice any longer.

Back to Roho.
I bought a couple of used Quadro Deep Select cushions that were 19.5 wide and 20.5 deep. That is because they are damned near the same size as a 18 x 20 Jay cushion. Dont ask me how that works but it does! Just 0.5 inches wider/longer and the same height. A fraction taller buy you sink in further.
Roho, when the deep one is used (theres 3 heights) like the 4 inch deep ones I ordered (£110 and £140 on ebay each) then they offer probably the best ulcer prevention of any chair on the market. Again I personally hate the Rohos. Because of a bunch of things I will mention below.

Good points.
Best protection you will get from sores. Cool. Light if this matters to you.

Bad points.
I transfer sideways, usually with a board. Since everywhere on the cushion where you press sinks to the base this is almost ompossible. And risks the small individual cells getting damaged too. Stability. Compared to the Jay2 above, is abysmal. You wobble around like a jelly and its hard to do anything physical properly in comparison even with that quad iso thing valve shut. And I do some DIY stuff. I have hot solder, sharp shrapnel (swarf) from drills and lathe and today was cutting a bit of steel on my knee with a grinder. You can imagine what happens with an air cushion... With a super thin easily melted cover needed to make best of the air cells. Thats why I got 2. That and I bid and won both! More bad. Maintainance. You are SUPPOSED to sink in these right to the bottom except for 20mm. And this is supposed to be checked daily. Looks easy on the vids! Its not. Its hard to get 2 people to agree even with their own tests! So its very hit and miss. And you have to mess around with the air pressure to adjust this with a pump.

Several people said that they just pump up, undo the valve to let it empty the air until its equal to atmosheric. When I try this, I am sat too high. And need to sit on the cushion and release a fair bit more before the hand test is correct. So that doesent work for me. But I have a digital way of dealing with this requiring no more hand tests!

Which I will add here soon.
Do they help with the ischeal tuberosity problem? I will update this page when I know. Right now untried.

Watch!


youtu.be/V_iAeYnjnXY


youtu.be/Ea7jGaspB4Y


youtu.be/pF-U3IDLgJk

Her voice!


youtu.be/ugpmKWP9J1k

[Burgerman]

Now... Considering that I am not using the ROHO above for fun. And that to make best use of it requires the the amount that you sink into the cushion is correct, and that too deep causes the very opposite of protection as you bottom out, then its pretty important that we get this right.

Having already discovered that the same carer when doing the daily HAND TEST in a plastic bag gets different results every time. And that all three of my carers also get different results to each other I decided that there was a problem! Several in fact...

So I plan on doing the following to get this correct easily and long term. And without having to do all these daily or even weekly HAND CHECKS. (If you dont know wht a hand check is, see the vids above. They are a damned nusance. You could just guestimate, as several users told me by allowing the cushion to be at atmospheric pressure by pumping, removing the pump and just waiting a while. Then close the valve. But I tried that. It results in a much greater than the proper 20mm gap between my backside and the chair. So not really good enough. And then theres temp. As you sit for 8 hours or more it gets warmer. Air expands. So the temp of the room when you did that test makes a difference.

So I have a digital plan. I bought a digital U Tube or manometer.

Measures very low pressures accurately.

They accurately measure really low pressures. Typically 2psi MAX. They are accurate to a very high degree on really low pressures. I am fitting a T into the pipe from a small high quality alloy bicycle pump. The Roho plastic ones leak air through the piston seal and so are not good enough for this job. This 3 foot long thin tube goes to my digital manometer pressure guage. So that when sat on the cushion, in the corect postion, I can read off the pressure to an accuracy of around 1%. Now once you are sunk into that cushion the pressure changes between say 0.5 inch clearance and 2 inch clearance doing the hand test are pretty small. But very repeatable. So...

I will over inflate. Sit on it. Release air a little at a time while my carer does the hand test thing. I will read of the pressure when he/she thinks its at 20mm. And make a note of the pressure reading in mm of water or whatever I choose. I will then over inflate the cushion and repeat. I will do the same thing when I get OFF the cushion (take a reading and do the feel test) too as it will now be warmer. Then I will get my other carers on their shifts to do the same. After 1 week I will have a 28 readings. They will all vary a little. But I can throw out any outliers. And can aversge all the rest to give me a mm of water pressure reading that equates to the correct pressure. From then on I will not need to check anything but pressure while seated during the day. Maybe 3 times a week or less. No more hand test needed. I will know that x mm/h2o = correct hand test. And it will take seconds. Couple of mm low? Half a pump... Unscrew.

https://www.amazon.co.uk/gp/product/B01 ... UTF8&psc=1

https://www.amazon.co.uk/gp/product/B08 ... UTF8&psc=1

https://www.ebay.co.uk/itm/Brass-Reduci ... 2749.l2649

https://www.ebay.co.uk/itm/200cm-2m-x-3 ... 2749.l2649

You need the 4 things above to do it neatly. The tube and the T is so you can pump and monitor pressure while sat back in the correct position. Theres a reducer from 4mm (the 3.5mm pipe used on pump/and washer systems, same stuff - fits) and the smaller diameter 3mm stuff used on the pressure monitor.

[Burgerman]

RESERVED

[LROBBINS]

Copied from another thread into this new one:

Hi John,

When you get your roho cushions consider adding a surround as Rachi has on both her current chair and the one nearing (FLW?) completion. Rachi and her aide are off somewhere, so I can't show you this with the QuadtroSelect in it, but here's a pic of the one on the new chair:

It's just glued together from 3 pieces of 8 cm high 2mm ABS, and really improves stability without compromising immersion in the Roho.

BTW, Rachi has the same cushion for nearing 20 years with never a leak and almost never needing to have air added (except for after we bleed it down a bit when traveling by air - gets a bit hard when not at sea level). Of course, she doesn't have a lathe and drill press in her bedroom! She had used a series of Jay gel cushions, which got hard every few years, but when she reached puberty started to get pressure sores with that. We tuned the Roho pressure to 100% "green" while she was sitting on a pressure mapping pad, I stuck my hand in a plastic bag and slid that under her knuckle side down to get a feel for that, and that's been a perfectly adequate way to keep track of it over all these years. Zero pressure sores since then.

NOTE: on the thread where this was originally posted it was pointed out that this surround is a NO NO for side transfers. Good point.

Instead we've had to do battle with friction sores caused by her scoliosis brace - she's fighting one in an armpit at the moment, but the worst was one some years ago that eroded the skin over her baclofen pump - the pump had to be removed to let her heal, then a new one implanted. I think that I've finally found a solution for preventing this, but getting rid of an existing sore just ain't easy as you well know.

[Burgerman]

I do!
I am now testing (will be soon) 2x roho deep select quad cushions.

I hate the squashy edges that literally prevent transfers with a board/hands for me. So Roho = using a sling and a lift which is too much trouble and time. But it appears I no longer have a choice so the box shown in your pic may be useful regardless. And yes swarf, metal, dropping scalples etc between legs when working is a hazard with roho.

I also have an idea for doing away with the hand in a plastic bag evety morning. I used to service Gas heating systems. And used a U tube for pressure. I have a £36 modern digital device on the way. It measures accurate presure in the 0 to 2psi range in 5 different units. I think from some maths on a mat that when seated on a roo the pressure will be between .5 and 1psi. So:

So I have thrown away the Roho pump. (they leak air around the piston. Not good enough for what I am doing) and bought an alloy small 6 inch bike pump. It doesent leak. Now... I have a push in plastic T in the rubber tube that goes from pump to the roho air valve. The T has a small 4mm rubber tube, 3 feet long that goes to my new digital low pressure guage from Amazon. So that I can undo the roho air valve, and read the pressure accurately. And with better non leaky pump I can wait as long as I need to let things stabilise etc. So I overfill with air, then reduce pressure until carers fingers in plastic bag are correct clearance under my backside. And then take note of exact digital pressure when everything is correct.

So now, all I need do is check pressure to know if it needs less or more air volume. This works because while pressure doesent change much it does change enough for this to work well. As long as the figures are accurate.

Guage https://www.amazon.co.uk/gp/product/B01 ... UTF8&psc=1
https://www.amazon.co.uk/gp/product/B08 ... UTF8&psc=1
And
https://www.ebay.co.uk/itm/200cm-2m-x-3 ... 2749.l2649

All adds up to an easy way to do the hand test just once. And then not needed ever again. You do need to set the roho isoflow valve thing OPEN while you test or measure though. And close it later on.

[Yennek]

If you don't like the squishy sides, have you checked out the roho hybrid options? My wife tried one (can't remember which) but preferred the normal roho, but to each their own.

http://permobilus.com/products/seating- ... id-series/

[Burgerman]

I physically looked at one. And didnt like the way it was constructed. And actually ordered a Jay balance or whatever it was called which has a roho rear section the same. But still not as much protection and immersion as the deep roho. So I went with that. Since I intend using a hoist from now on.

[Burgerman]

.

[woodygb]

I have hot solder, sharp shrapnel (swarf) from drills and lathe and today was cutting a bit of steel on my knee with a grinder. You can imagine what happens with an air cushion... With a super thin easily melted cover

You could invest in a kevlar apron.
https://www.u-buy.co.uk/catalog/product ... t-length-x

[Burgerman]

Might be wise! Right now I am laid in bed. But surrounded by the swarf from drilling holes in a steel bracket for my DIY mower... And its an air bed with a single sheet.

[Frank]

Roho has smart serious cushions to easily check the inflation of the cushion. I do not know if they are any good? But they are more expensive.

[Burgerman]

I saw those. They gave me the idea. But they work over a wide range. And dont tell ME what range of pressures it deems acceptable. And it also doesent fit/work on any of the Quadro cushions only on single chamber ones. Its gor a strange quick release thinky that only fits special cushions. And I really cannot use those! Presumably because it thinks we as users are too dumb to open the isolating valve between the 4 sections to do a test. Or maybe because you leave it connected. And so would only measure 1 quarter.

I lean sideways to reach something on a single chamber roho and all the air goes to one side! And The low side of me hits the base. OK if you sit still. I know this because in the past I have had a single chamber and a quad chamber cushion kindly provided free from an importer a decade ago. I didnt use either other than testing because transfer/stability issues. And gave the single chamber one to a freind who was struggling with sores. Or rather housmaids arse as he called it. Because of some fluid. And sold the quad chamber select one on here. And the smart one has also got a rather high price!

I think I can do better and do so much cheaper with actual known pressures. But it wont be an always on monitor. I can use the WCS pressure map, and adjust pressures to get the best mapped result. Although I am not entirely convinced those are much help. But its another thing to consider. I can measure absolute cushion pressure. Or Atmospheric/cushion pressure difference as its a 2 port device. Which is more use as the atmosphere varies with the day. And the altitude. I live on the coast. If I drive inland the cushions pressure will rise compared to the atmosphere. So the actual correct pressure will go up or down with the barometer. This device lets me see and deal with that.

There was a very careful bit of research done here that compares cushion pressure with ass pressure! That I just found a couple of mins ago. Still reading it. It gave me some useful info. Such as the pressure that your backside begins to die! Link below. But it appears to say that there are specific pressures that close the capilliaries and stop bloodflow pressures. And that basically doing almost exactly as I planned above allows you to see this. And stay below that figure. So it appears my plan is a good one. And it is going to be plug and play. Just needs some mental knowledge.

Have a slow read of this. Its very very interesting. https://www.resna.org/sites/default/fil ... Hefzy.html For their users, a cushion pressure of .62 and .63 psi, eqates to the best result for each user. And it gives a ass pressure of 32mmHg - on their LOW roho cushions:

The closing pressure of arterial capillaries is 32 mmHg or 0.62 psi (1 psi = 51.71 mmHg) which means any pressure higher than this exerted on the capillaries will cause an impediment in the flow. This gives a target for reducing the pressure to as close to 32 mmHg as possible.

It appears that all I really need to do is keep cushion pressure at .62psi or below to keep bloodflow moving. And be sure that .62psi is not low enough to cause bottoming out. They are using a low roho. So I should have more lattitude too. Maybe lower than .62psi and so less pressure on skin. The lower that we can get, without bottoming out, from 32mmHg the better. It allows controlled and independent adjustment without a carer needed. I should be able to set a lower pressure with a deep cushion with a safe 20mm between chair and ass. We will see.

[rollingcowboy]

I have found an easy way to set the ROHO Quad. When off of the cushion over inflate with the chamber valve open so all 4 corners are over full.
Leave the inflate valve open and then just let the cushion deflate for about a minute, long enough for the cushion to settle and equalize to room air pressure. Close the inflate valve and the chamber valve. This works very well for me. This method gives me a little bit more than a finger clearance.

[Frank]

I have found an easy way to set the ROHO Quad. When off of the cushion over inflate with the chamber valve open so all 4 corners are over full.
Leave the inflate valve open and then just let the cushion deflate for about a minute, long enough for the cushion to settle and equalize to room air pressure. Close the inflate valve and the chamber valve. This works very well for me. This method gives me a little bit more than a finger clearance.

That looks a very good idea and a simple way to adjust the cushion. I presume that this is also good for a one valve high-profile Roho cushion.

[LROBBINS]

0.62 psi must be the differential pressure - cushion absolute pressure minus atmospheric pressure. 0.62 psi is only about 4% of atmospheric pressure and rollingcowboy's method probably comes pretty close to this.

[Burgerman]

Well when I tried the way rollingcowboy says to do I ended up with very little immersion. And a higher measured pressure. Around .65 to .69psi. When I dropped the pressure to .6 psi I was still not immersed enough with the hand test. With the thicker 4.25 inch roho and my fat backside its possible to drop pressure well below the .62 by maybe another 10 to 12 percent.

When I tried the same thing with a carer with less backside leaving more cells unused, then doing it rollingcowboys way is better. But it still results in less than ideal. It can be lowered/immersed deeper and at a lower pressure. Presuming that cushion pressure = backside pressure too (it was very close on the expreriment/research done in the link above but not actually the same?) Then you need to squash out maybe 1/4 of the air before sitting on it. They were using a low profile roho. So likely couldnt lower the pressure as far either. I suspect that when I get a better chance, the pressure will end up at .57 ish psi as the correct safe hand clearance. And thats below the capiliary/artery crush pressure. 0.62 is at that point. Above this is unsafe.

So its definitely a better way than guesswork. I need to do more experiments my T and tube only just arrived! So now it will be easer to do. Yes .62 above ambient. I can either zero the meter every read/day or just set it to measure difference. One side open and other side cushion.

Also PSI is easy but its way more accurate to these small changes to use millibar or Pa. Millibar is what I am used to when fitting gas boilers! So I get that easier!

So will likely use this in future. Capilliaries crush and blood flow stops at 32mmHg. Thats 0.62psi or 42.747millibars. So any lower than this that you can get, without bottoming out the better! And its possible with the high roho I think if you are careful with setup.

[Burgerman]

Frank. Yes it works the same on the single chamber roho. When setting pressure and testing with hand initially the 4 chambered one is set as a single chamber anyway.

With one proviso. You dont lower your pressure too low. Because with a quadro cushion you can lock the correct pressure in each chamber. So you can safely sit a little more imesred or lower. Because when you lean left/right or lean back or forwards the air cannot move around. So you are in no danger of one side bottoing out for e.g.. Just be sure that as you lean left and right, that theres still adequate safe clearance via a hand test. Then yes good to go. Thats very similar to the auto one that tells us nothing that their smart cuchion monitor does. Be unteresting to know what pressures it regards as too high or too low. It must have a "safe" range of pressures built in that covers most users sizes etc. I dont trust it though. Because a small person sinks deeper than a fat one at the same pressure on the same cusion. So not sure how safe their settings are. Obviously it cannot be optimised for all.

[garriew]

Have you considered a Vicair cushion? https://vicair.com/

I'm considering one.

[Frank]

After you have adjusted the Quattro Roho cushion when should you close the isoflow valve, after you sit on the cushion or before?

[Burgerman]

Directly after you are correctly seated and checked the pressure is the same as when you did the hand test. So if pressure is at x you then shut the valve. Better if someone else does it so you dont move the air around leaning.

[Burgerman]

Have you considered a Vicair cushion? https://vicair.com/

I'm considering one.

The iBot chair that I tested in pre production came with one. JJ were planing on supplying these as the stock cushion. I didnt like it... And it did leave me with red marks on the isheals after a days use. So its ok as a reasonable pressure cushion low risk clients. Its not as good for extreme risk or for those with previous history or ongoing sores. As far as I could tell. I revertd to the jay2 and used that on it instead. Your mileage may vary. But not enough immersion for low pressure. But your needs may not be mine. Note this was a long time ago. Current models are pretty much the same tech but offer different compartments etc.

Pros. Stable platform. Reasonably easy to transfer. Good ventilation. Light. Low maintainance.
Against, ultimate pressure relief maybe/is worse than the common gel Jay2 and definitely worse than is possible with the Roho.

[ex-Gooserider]

I use a Supracore "Stimulite" Contour cushion, 18' x 18" I've also used (actually still do, I have several of these and rotate them as I need to wash them) the Contour XS version.

Both are silicone(?) rubber 'honeycomb' cushions, and the same basic 'butt' shape. The claimed theory is that the cells in the honeycomb collapse under the areas that are loaded more heavily and less so under the light areas, so that you end up with uniform loading over the entire sitting surface. It isn't perfect, but seems to work pretty well when I've done pressure mapping... I got a slightly better mapping w/ a ROHO, but not by much, and I have the same sort of concerns as BM about the (lack of) stability, transfer problems and vulnerability to shop debris...

The cushions have multiple layers of honeycombs that vary in how hard they are, with the thickness of the different layers changing in different parts of the cushion.

The big difference between the regular and XS versions is the XS version has a layer of softer honeycomb on top, I find that I seem to fully compress that as soon as I get on the cushion so the regular version seems to give me a little bit more support.

I seem to sweat a lot, and with any of the cushions I've tried that have 'incontinence' covers my butt ends up soaked... The standard Supracore cover is a breathable fabric (feels like polyester or similar synthetic) and the honeycomb is breathable. Supracore claims that the honeycomb is actually designed to have a 'pumping' effect when the user moves around in the chair, or is moved by the chair movement when going over bumps, etc. that increases the air flow.... Either way my butt stays a lot drier when sitting on these cushions. Downside is that if one has an "accident' (neurogenic bowels are SO annoying that way! ) the cushion gets soaked... However the cushion and cover are all machine washable, and machine dryable (the machines have to be large and non-agitator style to handle the cushion) but I find that it works if I just hose it down w/ plenty of soap and water in the shower. It then takes a couple days to air dry, so having enough to 'rotate' helps. They also seem to lose some of their support after a year or two (or at least that is what the insurance will cover....)

I've never had a cushion related pressure sore... I had a small sore on my coccyx in rehab from the shower chair (solved by rotating the cushion to a rear opening) and a weird thing from "necrotic fat" on a non-sitting area of my butt shortly after I got out of rehab.

I have tried several cushions in the first few years after I was hurt and none really worked well....

When I tried a single chamber ROHO I also found that other than boosting completely off the seat I couldn't really do any sort of pressure relief as the air just moved around as I shifted so the pressure points stayed the same. I didn't try a fancier pump, but the stock "jumbo syringe" style pump needed so much effort to operate that I could not inflate the cushion while on it. (I found this out when a slow leak in the valve left me bottomed out) I consider this dangerous, especially if you don't have enough feeling to be able to tell that you have bottomed.)

I tried one of the 'hybrid' foam / air cushions (I forget the exact brand, it is still sitting in the back of my closet somewhere) and it was OK but not great, especially as it was hard to get the air pressure right. It did have a MUCH better pump setup. It used a squeeze bulb like a blood pressure cuff, and that didn't move a lot of air per squeeze, but the effort was low and it was easy to pump it up while sitting on it... The bulb was also compact enough to fit nicely in the front pouch of the cushion.

I also tried a couple of different foam / gel cushions like the Jay type, and found they mostly weren't comfortable, primarily because they didn't allow any air circulation to dry my sweaty bottom...

ex-Gooserider

[Burgerman]

ROHO PUMP/GAUGE TEST. From above.

If I adjust the roho to the point where they say at 3/4 of an inch, 20mm, then I get the following pressure in the cushion:

0.535 to 0.542 psi as you move your head about! Thats with arms rested on the chairs arms. It increses to 0.590 0.600 with arms lifted up.

0.62psi is the same as the 32mmHg pressure that stops blood flow. So its pretty critical.
Adding 1 inch of foam below the cushion made no difference that I could detect.

Going from 3/4 inch 20mm hand test to 1 inch (25mm) puts all the pressures above the that 0.62psi point repeatedly. 3 tests.
Going below that 3/4 inch hand test measures better. At a half inch, or 12mm but I dont feel safe from bottoming out. But it is a lower pressure still. And around 0.520psi.

I intend doing this on a daily basis with different carers and then avearging all the figures to get a more accurate "centre" pressure. At that point I will know what pressure to set, can see this as I release air or add air while sat on my cushion. So I think this is a great way to set the correct pressure, be sure you are below the critical limit of 0.62 where circulation is stopped or can be. And removes all the subjective carer/hand test error.

If you are a roho user with any skin issues then this must be a definite go to method. Its cheap, and extremely informative and accurate and repeatable. Will post pics soon. These figures were for a 17 stone adult male on a 19.25 wide x 2.5 deep x 4.24 high 4 chamber roho. Thats 10w x 11d x tall cells.

To convert to PA, Inches/water, mm/water, cm/water, mmHg, cmHg, kpa, millibars etc etc this meter does it. It can read peak values, averaged rolling values, (useful as it moves a lot as you move or breath) and hold, and backlit screen, and both absolute, and difference in pressures, and more. You can convert these to your favorite scale here: https://www.onlineconversion.com/pressure.htm

[ex-Gooserider]

One of the things I have heard about Roho's is that it is absolutely critical that the size of the cushion match the size of the butt that is sat upon it...

If the cushion is bigger than the butt, all the air moves to the un-sat-on cells and the sitter bottoms out unless very high pressures are used...

If the cushion is smaller than the butt there is no place for the air to go, so you end up w/ higher pressures in the cushion, while the excess butt droops over the edges...

The cushion needs a 'Goldilocks' style fit that is "just right"....

ex-Gooserider

[Burgerman]

I would agree. And I can measure this. Small female carer needs more pressure to not sit too low. Instead of the opposite. Same on gel cushions.

[Burgerman]

Roho deep cushion, 19.25" x 20.5" deep. (10 cell wide x 11 cell deep x 4 inches tall) With 15 mm between lowest point and chair base. Averaged over a week 3 different carers. They are lighter and skinnier than me! So these figures are not yet accurate for me personally.

(28mHg) arms on armrests averaged although fairly consistent.
(31mmHg) arms lifted up also averaged and rounded to full digits.

Acceptable limits of peak pressure (generally over the ischial tuberosities) are 40-80mmHg if pressure is regularly relieved. Every 15 to 20 mins. According to many studies. People vary. This is from mapping via a pressure mapping services and lots of studies.

Safe pressure is around 27 to 32 mmHg without damage in several online pressure mapping clinical trials. And this is hard to achieve. Only the deep roho seems able to match this figure regularly with careful setup.

Considering that in a roho the pressure is always equal throughout the air cushion then the actual measured pressure is = to the pressure on your backside or a pressure mapping result.

One is a part of an ad for a water cell cushion. The pressure data is still equally useful.

So it seems the correct inflation pressure is that witch has 20mm gap between ass and seat pan. And it will HOPEFULLY be below 27mmHg. If not, go on a diet, get a smaller cushion that allows you to cover most of its surface, use wedges on outer edges or a 1 inch foam layer below with cutouts for ishial tuberosities below the deep roho allowing lower pressure before that 20mm is used up. Or whatever it takes.

More useful reading.

[Burgerman]

Now I want a pressure mapping setup. I tested one and played with it many years ago at the spinal injuries unit. Its a tool. Its not everything. But its useful. I did not realise then, quite how critical these pressures are, and how important the peak pressure on the ishial bone area was. It is ESSENTIAL to get this cusion pressure below 27mm of mercury. This was before I found out the cost!!! These things are REDICULOUSLY expensive. You can buy a new car cheaper.

So any idea of a mapping setup that is AFFORDABLE?

Have a careful read here download/file.php?id=15025

Is it a potential DIY project?

[ex-Gooserider]

Now I want a pressure mapping setup. I tested one and played with it many years ago at the spinal injuries unit. Its a tool. Its not everything. But its useful. I did not realise then, quite how critical these pressures are, and how important the peak pressure on the ishial bone area was. It is ESSENTIAL to get this cusion pressure below 27mm of mercury. This was before I found out the cost!!! These things are REDICULOUSLY expensive. You can buy a new car cheaper.

So any idea of a mapping setup that is AFFORDABLE?

Have a careful read here download/file.php?id=15025

Is it a potential DIY project?

I could see a DIY project, but it would not be easy... SOME bits might be off the shelf, others probably not...

The toughest thing to duplicate would be the sensor 'mat' that goes under the user... Probably the most expensive part as well.....

Basically the mat is a fabric sandwich of load cells in a matrix... A Duck-Duck search for "ultra thin load cell" gave lots of results like this... http://forsentek.com/prodetail_385.html . At a guess, I'd estimate the mats I've seen have at least one cell per square inch, so for a 20" square mat, you'd be looking at around 400 cells - and they are NOT cheap... Probably on the order of US$10-15 EACH

Then one needs to work out the electronics needed to scan the matrix of cells - probably something on the order of a key-board controller or a touch screen reader might work. It would depend on the way the cell output it's signal, etc... The reader would then need to convert the data into something you can feed into a PC, probably a USB output.

Lastly you'd need software to turn the data into a display - I suspect this would probably be the easiest and likely exists as all it would do is convert the value from each cell into a color, and paint that spot on the display.....

Not inclined to take it on as an actual project, but that would be my take on what you'd need....

ex-Gooserider

[Burgerman]

Its worse... Most cushions are 1024 sensors. Rohos one is 1380 sensors. And costs 10s of thousands of dollars.