Monday, November 19, 2018
Power Seat Functions: We want to hear from you!
Over the past 3 weeks we have talked about drive wheel configuration and some tips on how to decide which option is right for you. This week we are going to discuss power wheelchair suspension. The suspension can vary from chair to chair even within each manufacturer, but there are some key points that we should discuss.
Most power wheelchairs on the market are going to use compression springs for their suspension. There are two types of compression spring that are typically used: Linear and Non-linear.
Non-linear springs as seen in the photo below allow for changes in compressive load at different points of the range. What this means is that you can have the looser spring coils at the beginning phase to help with climbing over obstacles. The trade-off will be that you will lose some of the overall stability of the chair when not climbing. Many manufacturers will use one non-linear spring as their suspension.
Linear springs on the other hand allow for consistent stability throughout the compression range. For Permobil, these springs are also adjustable. The factory will set the suspension spring resistance based on the weight of the user and then the supplier or manufacturer representative will have the ability to further adjust depending on the needs of the user. With the Permobil M and F series, the suspension will be composed of multiple linear springs to achieve optimal traction and suspension.
Why does this matter? The shape and the coil distance have an impact on how a spring works and effects the user. The better the suspension, the greater the decreased forces on the end-user. This could lead to increased seating tolerance, pain management, spasticity management, and decreases the risk for loss of balance or position in the wheelchair. One of the biggest points that I think about is driving over any uneven terrain whether it is just a sidewalk or grass at a park. It is important that as the chair goes over each bump that this bump is not felt by the user or limited as much as possible. If each bump is transmitted up to the user, then the user will likely not maintain their seated position. They will also feel all this vibration. According to one study by Wolf and colleagues in 2007, this vibration can lead to many impairments including fatigue and pain.
The final thought that I believe is one of the most crucial points to make is that the suspension on the wheelchair should always be there for you or your client. We know how important suspension is and the negative impact that not having this suspension could be to our clients. Therefore, we need to make sure that the wheelchair will maintain its suspension in any position and over all surfaces. No matter what position the user takes the Permobil power wheelchair to, such as elevate, posterior tilt, active reach, or standing, the suspension remains the same. If you want to drive your wheelchair in elevate, active reach, standing, or other positions, you want to be sure that your suspension will continue to support you in those positions and not lock out.
It is important to know that each manufacturer will have different suspension set up on their chairs. As a client, therapist, or carer make sure you ask about the suspension to determine which option is best for you.
The drive wheel on a power wheelchair is the larger wheel if you are looking at your wheelchair or client’s wheelchair. The location of this drive wheel can have a large impact on how the power wheelchair drives and manoeuvres in different environments.
There are three main types of drive wheel configurations on power wheelchairs: front-wheel drive, mid-wheel drive, and rear-wheel drive. In this blog today, we will focus on mid-wheel drive.
The mid-wheel drive power wheelchair is the most recent technology developed for power wheelchair bases. It attempts to combine the positive aspects of front-wheel and rear-wheel drive into a hybrid product. Mid-wheel drive has many benefits. The most well-known benefits being the small turning radius and intuitive driving. The mid-wheel drive power wheelchair has the smallest 360 ̊ turning radius which can improve manoeuvrability for many individuals in their home or smaller spaces. The intuitive driving benefit is due to the placement of the drive wheel. Typically, in the mid-wheel drive, the client will be sitting directly over the drive wheel, which is where the chair will turn/rotate from. This axis of rotation being directly under the individual is what makes the driving intuitive or often people will say “easier to learn”. It is important to remember that in some cases the mid-wheel drive may not line up directly below the client and therefore may lose some of that intuitive driving. The final benefit to discuss for mid-wheel drive is the stability. Because a mid-wheel drive wheelchair has 6 wheels on the ground, this chair will offer superior stability. This can be the case whether ascending, going up, or descending, going down, ramps or inclines.
While there are many benefits for mid-wheel drive power wheelchairs, there are a couple considerations when deciding if mid-wheel drive is right for you or your client. In being a superior option for stability, the 6 wheels on the ground also means that more energy from the ground is transferred to the client. Imagine going over a bump, because there are 6 wheels you could feel that bump 3 times versus the 2 of the front-wheel drive. This could potentially limit the ride comfort for the individual in the chair. Luckily, depending on each manufacturer, we have suspension to help decrease the impact of having 6 wheels on the ground. I LOVE talking about suspension and we will have a blog post coming soon to talk all about suspension in power wheelchairs and the importance of the suspension. The other comment I hear about mid-wheel drive power wheelchairs is the potential for “high centring”. This term is used to describe when the centre drive wheels lose traction and may not be able to move in certain situations. This is particularly a risk with uneven terrain and was previously the biggest disadvantage of the mid-wheel drive power wheelchair. However, depending on your manufacturer, newer technologies and suspension can compensate and have greatly decreased the risk of this occurring.
The mid-wheel drive power wheelchair is the most popular drive wheel configuration and for good reason. As technology continues to progress, the mid-wheel drive continues to have greater benefits with less limitations.
Keep in mind that not everyone will benefit from the same drive wheel configuration and it is important to ask questions and complete an evaluation to determine which drive wheel would be best for you or your client.
“I go places and people look down at me, I would rather look them in the face.” – Mecenzi
If we have the ability to fully access and participate in our environment, we may forget that this human right is not possible for everyone. Think about your daily life. Can you reach the counter in your kitchen to make a sandwich, or reach inside the refrigerator to grab a drink? What about reaching up in your closet to get your clothes? That is just in your home. Now think about experiences in your community. Can you look face to face with your friends and family? Can you give your loved ones a hug without an awkward bend over shoulder in your face outcome? How about accessing counters at a restaurant to pay your bill? For many individuals with a mobility impairment their environmental access is greatly limited. It’s not just environmental access though. How would you feel if you had to sit down in a chair at a party while everyone around you was standing and talking? For some individuals with a mobility impairment, they find it difficult to fully interact with their peers when they are unable to look them in the face. For individuals with mobility impairments it might not just be accessibility and peer interaction but returning to or choosing a career path that typically requires standing throughout the day. While accommodations can typically be made, what if instead of adapting the environment we adapted the individual’s mobility device?
Today I want to share with you Mecenzi’s story of herself and her new F5 corpus VS.
Mecenzi’s story, as you will see in the video below, illustrates how with the assistance of the F5 Corpus VS, Mecenzi has greatly improved not only her independence, but how being able to stand up makes her feel.
Last week, we heard from Mal on the impact that Mr. Graebe and ROHO had on his life and he used the words “DRY FLOATATION™ Technology”. This week we are going to dive a little deeper into the design of a ROHO cushion and explain what Dry Floatation is. In designing the ROHO cushions, Mr. Graebe realised the best way to protect the skin would be if the client could be placed in water because of the benefits of floating. He knew that it would be impractical to achieve true floatation in a cushion, so Mr. Graebe concentrated on achieving the same type of floatation but used air instead of water. This idea developed into what is known as DRY FLOATATION™ Technology, and it’s a ROHO exclusive. Mr. Graebe spent many years in his garage working on his idea of Dry Floatation and in 1971 he released the first ever ROHO cushion – a high profile ROHO cushion.
The adjustable air-filled cushions and mattresses mimic the pressure relieving properties of water, removing friction and delivering stability and comfort no matter where you go or what you do. DRY FLOATATION™ Technology is based on 4 principles characteristics of water that causes floatation.
Here are the 4 principles:
1. Low Surface Tension – Fluids have very low surface tensions, which allow an object to penetrate its surface with little force. The ROHO design of many small interconnected air cells made of a soft, pliable neoprene rubber results in a very low surface tension. This limits the amount of skin deformation.
2. Constant Restoring Forces – both air and water have very small molecular forces of attraction that can be displaced. This displacement provides hydrostatic forces, or floatation, that are nearly constant no matter how deeply immersed the object is. What this means is that the ROHO cushion allows a person to sit immersed in the cushion for long periods without an increase in pressure over time.
3. Six Degrees of Freedom – Each cell within a ROHO cushion can move in any direction, allowing the cushion to move with the body, in the same way water moves. The result is that instead of the skin and underlying tissue deforming, the cushion itself deforms. This minimises both friction and shear forces.
4. Low Friction and Shear – Friction occurs when two surfaces rub together. The courser the surface, the more friction exists, increasing the likelihood of tissue breakdown. ROHO cushions and mattresses are made of a neoprene rubber that has been treated to reduce friction to minimal levels. Shear is a lateral force that occurs at a deep tissue level. This is the result of friction holding the skin in one place while gravity pulls the skeleton and attached tissues down. Shear can be a major issue when someone is lying in bed with the bed head elevated, or for someone seated with kyphosis and a posterior tilt of the pelvis. By minimising friction with the coating of the neoprene, as well as the size Degrees of Freedom, DRY FLOATATION™ Technology reduces shear forces.
Whether you are sitting on a ROHO cushion, you have a friend or family member that uses a ROHO, or maybe you have gotten a ROHO cushion for your client, hopefully you see just how much thought went into the design behind ROHO. We want to thank Mr. Graebe again for his contribution and positive impact on the lives of so many.
For more information on pressure injuries check out the Pan Pacific Prevention and Treatment of Pressure Ulcers: Quick Reference guide. http://www.woundsaustralia.com.au/ptpu/index.php
Rachel and Mal
In 1978 a young electrical engineer, Robert H. Graebe, was introduced to a patient with a pressure injury. He witnessed a doctor excise tissue from the site. The doctor’s comment “we do not know how to prevent these sores” left such an impression on Mr Graebe that it inspired him to find a way to prevent pressure injuries. As a result, he invented a new technology, DRY FLOATATION™ Technology, and a range of products named ROHO. Since then ROHO products have changed the lives of millions of people in 65 nations, enabling them to pursue productive, independent lifestyles.
On Saturday 15th September the Starkloff Disability Institute in St Louis honoured Mr Graebe with a Lifetime Achievement Award. The Starkloff Disability Institute is a non-profit organization dedicated to helping people with disabilities participate fully and equally in all aspects of society.
The award caused me to reflect on the impact Mr Graebe has had on my life. In 1980, at the age of 19, I was a passenger in a motor vehicle accident which resulted in a spinal cord injury at T5, complete. In 1982 I started to develop skin problems due to pressure, and in my research found the ROHO cushion. Ever since my first single valve cushion in 1982 I have been sitting on ROHO cushions. I have been using a ROHO Quadtro Select Mid Profile for several years now.
Thanks to Mr Graebe I have remained free of sitting acquired pressure injuries for 38 years! Mr Graebe’s invention has had a profound and life changing impact on me. It has allowed me to remain active, to successfully run a business, to play wheelchair basketball both here in Australia and internationally, to travel extensively, to meet fantastic people from all walks of life, to be a productive member of society, to be financially independent and so much more.
I have also been fortunate to work with the ROHO product line for 20 odd years. In that time, I have seen countless lives of end users, their families, and their therapists, improved by ROHO products.
One of the highlights of my career was the opportunity to meet and dine with Mr Graebe. I often share that on that occasion I got to thank him personally for saving my arse for all these years. I am so delighted that Mr Graebe has been honoured for his incredible work. What an amazing thing that he was moved to invent a product that would, and does, help prevent pressure injuries. He has truly changed the world of millions of people for the better. What an amazing legacy!
We would love to hear your stories on how Mr Graebe’s invention has had a positive impact on your life!
Madison de Rozario in her custom TiLite ZR
In the past two blogs have been discussing TiFit and the importance of a chair made to fit the individual. Today, we will be looking specifically at how we worked with Madison De Rozario to design a TiLite ZR made for her and her lifestyle.
To start the process, we met with Madi to find out what her life looks like: what does she love to do, what does she like about her existing chair, and what would she change if she could? Some of the key things about Madi mentioned included: her love for her dog (Sebastian), that she travels a lot, that she wants her chair to stay looking good despite her hectic lifestyle, to be “minimalistic”, and to be ultra-light, but very strong.
Despite Madi having an extremely strong upper body, her pelvis requires only a 285mm (11”) rear seat width. She really wants the front of the seat to be narrower, which follows the contour of her body.
So, we specified the chair to have a 37mm (1.5”) taper from midway down the seat to the front of the seat.
We worked out that, based on her arm length, 480mm (19”) is the best rear seat height for Madi, and that a front seat height of 508mm (20”) gave her adequate stability while allowing her to get under tables and desks. The seat upholstery to footplate height of 300mm (12”) is quite short in relation to her floor to seat height, and Madi wanted this to look as clean as possible, so Madi chose an open loop titanium footplate which needed to be custom made for her chair. We used the same rear wheel axle position as her existing chair and measured the overall length of her existing chair as this worked perfectly for her. Based on her frame length, overall length, and wheel base length the required front angle was worked out, using Computer Aided Design Technology, to be 83.5 degrees.
Madi also wanted her feet to sit nice and snug in her footplates, so measuring the width of her favourite shoes we specified a footrest width of 178mm (7”). Finally, Madi wanted her chair to be narrow at the front castors, so she can get into tight corners and use a “3 wheel” technique for going down the aisle of aeroplanes (with someone supporting the weight of the chair by holding the rigidiser bar at the back of the chair, one of the rear wheels is removed. This makes the chair narrower and able to be rolled down the aeroplane aisle, negating the need for an aisle chair. Because Madi’s chair is small, it also fits on the overhead locker of most planes). To achieve this, we specified a front castor width of 362mm (12.5”).
TiLite’s commitment to truly custom building the Z and T series chairs from the ground up allows for chairs like Madi’s to be made to fit her body and lifestyle perfectly.
Check out the video to see how the chair turned out.
We have been discussing the importance of configuration and how we want the wheelchair to fit like a prosthetic. To get this perfect fit, it is crucial that each chair is custom made to each client. We call this custom fit TiFit. Tifit includes all T-series and Z-series rigid manual wheelchairs. For TiLite, that means that when you order a TiFit wheelchair your wheelchair starts as a long metal tube. The photo is an actual photo from inside of the TiLite manufacturing plant.
Once your script is sent to TiLite the building begins. TiLite has the help of engineers and computer aided drawings to ensure that each chair is built to your exact specifications. You can even request a copy of your computer aided drawing, CAD, from TiLite that will show the exact measurements of your wheelchair. The photo below is an example of a CAD drawing from TiLite. Once the chair has been ordered and gone through the TiLite configurator, your wheelchair is then cut, bent, and welded into its final product.
The idea is that no two people are exactly the same, so why should your wheelchair be! The wheelchair should be made to fit like a prosthetic not pulled out of a box off the shelf. In doing this, we are ensuring the proper alignment of the shoulders to minimise the risk of shoulder pain and dysfunction. We are also ensuring that the wheelchair is comfortable, more efficient, and gives the ultimate performance. Next week we have the privilege to hear from Madison de Rozario and the importance of customisation of her wheelchair.
This week we are going to hear from Malcolm about his experience with his TiLite wheelchair and how important the fit is to him. For TiLite, the T-Series and Z-Series wheelchairs are a made to measure frame or as we call it TiFit. The TiFit chair is designed specifically to each person. We will learn in a couple weeks about the exact process that TiLite goes through for each T-Series or Z-Series wheelchair that is ordered, but first let’s understand from an end-user perspective why this matters.
As someone who is totally dependent on my wheelchair for mobility and sits in the wheelchair for an average of 12 to 16 hours a day, the fit of my wheelchair is critical for comfort, performance and aesthetics. There is good literature on the importance of custom built wheelchairs, for example: The PVA “Preservation of Upper Limb Function Following Spinal Injury” includes the recommendation “Provide manual wheelchair users with SCI a high-strength, fully customizable manual wheelchair made of the lightest possible material.” Today, I want to give an end user perspective on why this is important.
|There is no perfect analogy for this, but I will start with one anyway. For the first 25 odd years of my life as a wheelchair user, I just wore off-the-shelf clothing: jeans, pants, jackets, shoes, etc… Then, I had the opportunity to go to the RehaCare Expo in Germany and came across clothes made specifically for wheelchair users! The pants have no seams at the back, no pockets at the back, and are higher at the back to compensate for the seated position. The shirts are shorter at the front than normal shirts, but the back remains the same, which means they sit better in the seated position. The jackets are also shorter at the front and the sides, meaning they not only sit better, but they are not overflowing onto the wheels. I even found leather shoes with zips on both sides which makes them easier to put on and take off. Now, I love wearing clothes designed this way. The clothes feel better, I feel more comfortable, they are safer in terms of pressure care, they are more convenient, and I think they look better too. Can I get by with off-the-shelf clothes? Yes, but they are nowhere near as good.|
Madison de Rozario in her custom TiLite ZR
For me it is the same with TiFit. Of course, the prevention of upper limb injury is important. But the way my chair fits me perfectly feels better, more comfortable. It looks better, like I am sitting in it rather than on it. It is safer, knowing I can specify where my front castors are in relation to my overall length means it is less likely to tip over forwards. Being able to specify the width of the front castors means that I can get into the tight corners of my house, and bathrooms when I am travelling. It also means I don’t scratch my car as much when I am transferring in and out of my chair. Knowing that my front leg angle can be exactly what it needs to be to fit all my other dimensions means my legs sit better and do not slide off my footplates when I am pushing around. Add to this the fact that it rolls better, and you can see why TiFit is important to me