Sitting device to improve balance in stroke

Hello everyone,
I am an engineering student who is working on a semester long product design project. The project I was given is to design and build a device that will quantitatively evaluate a patient that has suffered from a stroke. I am no medical student so I'm not familiar with the correct terminology so bear with me please. The initial part of my project is to get input from people who might use this device. My initial plan/design is to have some sort of body harness with 2 sensors, one at the lower spine and one at the top of the spine just below the neck. I am looking for advice on where the best sensor location would be that would allow me to gather the necessary data so as to show a patients sitting position, sway pattern and speed of swaying. At this point I don't know if I can do this with only two sensor locations. The second part of the device will aid in the rehabilitation of the patient and help them re-learn a correct sitting position. I plan on doing this by audible signals that will help guide them to a correct sitting position. I may also do a visual screen that shows a 3-D plot of where they are and where they need to be - with respect to a correct sitting position. I know this is a lot to ask about, but any input will be greatly appreciated. As I mentioned before - I'm expected to find outside input to help in the design requirements for the project. To the best of my knowledge, there are only very expensive machines that monitor things like this for standing positions right now. My goal is to make a more affordable, portable device that will provide a more accurate way to assess a stroke patient's sitting position and help in the rehabilitation process.

Hi

Your idea sounds very interesting. There is a huge potential for engineers and designers working together with therapists to come up with affordable technology that can benefit our patients.

From what I gather you are saying this is a therapeutic device for a acute stroke patient who is unable to maintain sitting. Your device uses what we call in motor learning science augmented feedback, that is on top of the patients own feedback coming from their proprioception, vestibular and visual sensory systems you are providing extra visual information on alignment.

From a movement science point of view there are classically two ways of doing this: a device that estimates the combined centre of mass of the head arms and trunk and its vertical relation to the base of support (feet on ground and pelvis on sitting surface). If you had two position sensors as you described that were able to detect when they were aligned vertically be gravity this may estimate this. However I am not sure if this is the best way of doing it. The device would have to work in at least two planes (forward-backwards and side to side)

In terms of motor learning theory it is best if the information that the sensors provide is continuous or incremental not absolute. In other words the patient needs to know to what extent they are aligned or misaligned.

The second way to us the pressure sensors in the buttocks thighs and soles of the feet to estimate where the centre of pressure is - quite different from what you are intending.

By the way with most stroke patients gain the ability sit and maintain balance fairly early on but more will struggle with standing so from a therapeutic point of view I would be more interested in a standing alignment/balance device rather than a sitting/alignment/balance device. However that doesn’t sound like your brief.

In designing this I think it is worth trying to understand why an acute stroke patient may have problems with this. In the common types of strokes difficulties may arise. There are lots of things that can go wrong and contribute to this problem but some of the common scenarios are:

1. due to weakness issues in the trunk and lower limbs which is usually highly noticeable on the opposite side to the side of the lesion in the brain

2. a disruption of the correct perception of the vertical and being able to align based on any combination of Proprioceptive, vestibular and visual information

3. One particular version of 2) above is known as pushers syndrome. In this case the patient wilfully pushes their weight to the most affected side even

4. Another variation of 2) above is the patient who neglects, or fails to pay attention to information about their body position in space.

5. Loss of sensory systems so that there is a lack of information coming in (eg one-sided blindness, loss of sensory pressure on the thigh, loss of proprioception in the trunk and leg or loss of vestibular information) – in this case a very simple visual feedback system may work.

The final thing I would like to say is to work in a team on this. Why not see if you can get linked up the neurology physical therapists at your local university that offers a physiotherapy programme. In my experience with these type of things you need to include:

1. You, the designer/engineer
2. A person who can provide appropriate human factors or ergonomic information. Some therapists may be trainined in human factors engineering ergonomics or you may have such a person in your Engineering school.
3. A physical therapist working in the area who can would be one of the consumers and would set it up on a patient and would also be able to evaluate the results.
4. Trial/mockup on some patients – as consumers

For your invention to be successful I really think you need to take this team approach seriously. Don’t just rely on feedback from a website.

All the best with your project.

gcoe,

Thank you so much for your input on my project. I am one of three engineers working on this design project. This project was given to us by a physical therapist at a local hospital who also teaches at my college. She has given us input on what she would like the device to do and at this time the device will be specifically designed to be used on patients in the sitting position only.

Without getting into too much detail, the sensors I will be using will work similar to ones found in the nintendo Wii hand controllers. They can sense what direction they are moving in and will be relaying numerical position data at least every 1/10th of a second continuously so that I can map and record the patient's position, movement, and path. I am also meeting with a movement specialist along with a few other physical therapists that work with patients who have suffered from a stroke or head trauma. The online information that I'm gathering here is so I can get input from people outside of my local area. I am wanting to learn specifics on how other therapists evaluate their patients when looking at sitting position and sway. I am being told by the sponsor of this project that at this time they evaluate their patient's condition by having them do specific tasks and rating them on a poor, fair, good, normal scale (I know this is over simplified and incomplete with respect to the types and extent of testing used). This makes the evaluations somewhat subjective . The goal is to provide numerical feedback for these types of tasks. It will help to more accurately keep track of a patient's progress during rehabilitation and to better express the severity of their condition.

I know very little about this field of treatment - or any other medically related fields. The sponsor said that many of her patients will sit slumped over to one side thinking that they are actually sitting upright. It could be from physical weakness like you had mentioned or from some brain impairment. The sensors will be able to be set to a "zero" point showing what would be a correct sitting posture, and all measurements will be taken from that point of reference. To me, this seems like an odd assignment for a mechanical engineering student - but it's the task we were given.

Hi fordfornow77

Thanks for your response. It sounds like you are going about this in a systematic way which is great! And on the contrary: it sounds like an excellent task for a mechanical engineering student! - it is one of those areas which needs a multidisciplinary approach. As therapists we might know what the problem is but don't have the means to solve it by thinking creatively about new applications of technology - so that is where we need guys like you to help find solutions.

I wondered if you had read much about models of balance? I am attaching a couple of papers you might find interesting. Both papers are written by excellent researchers in the field and provide a review of components of balance. Unfortunately both are written more for the balance in standing and mobility but most of the underlying principles would be applicable to balance in sitting.

I use Fay Horak's model of components of balance as a way of ordering the assessment. Each component should be assessed seperately and your tool could be used in the employment of each component assessment. Hre are some examples but there are others:
1. the biomechanical constraints component could include managing to stack the body segments appropriately to maintain quiet sitting - so managing to find the "zero point" for your two sensors may be the goal.
2. For the Stability limits and verticality aspects you could see how far the patient can move the sensor in a given direction without loosing balance while reaching for various targets (repeated in different directions), and then ability each time to return to the "zero" position.
3. Sensory strategies could be determined by repeating that quiet sitting task but with different combinations of eyes open and closed and sitting on a soft surface vs sitting on a hard surface. Sitting on a soft surface makes reliance on somatosenory proprioception harder to rely on so you are testing the if the vesitbular and visual systems are being intact or being processed properly. Eyes closed means you have to rely on your vestibular and/or somatosenory proprioception.

Your tool could help quantify such an assessment.

Another thing that might be a useful contact: Mindy Levin, a PT at McGill University, Canada came over to NZ earlier in the year and gave a talk on New techologies of motor learning and recovery. She reviewed a number of commercial and lab based Virtual reality - she has done a lot of work on this over the years and had a wealth of knowledge about different systems, what worked what were the limitations etc. So you might like to try emailing her. Her website is:

Faculty: Mindy Levin

Dear Calico,

You will find some usefull information on the following website as well.

ICE Learning Center | A Leader in Clinical Education Since 1983
Do not worry about it being a site for therapists.... browse and take a look at the videosamples.

By subscribing to Jan Davis´s newsletter you will be kept up-to-date.

kind regards and good wishes for the future

Esther

Thank-you, the websites are really great and I am learning daily and it is helping.

A problem that we have at the moment is very stiff muscles. I know there is a terminology for it but forget it now. So, how do I approach this? Massage? Certain Movements? Different Positioning? I would much appreciate a few pointers here.

The very good news in our world is that I have found a good and competent and kind and experienced neuro physio that is willing to work with us. She is in another town but I will rent a temp house there and we will move to get experienced and competent guidance and help. But for a few weeks yet I am on my own.