Understanding the Cushion: Why it matters what we are sitting on?

Understanding the Cushion: Why it matters what we are sitting on?



Have you ever been to an event where you had to sit on hard metal benches for hours? They are so uncomfortable that many people bring thin foam cushions to help alleviate pain and discomfort. OR have you had to drive during a long road trip and can barely feel your bottom at the rest stop because it has gone numb? That is why truck drivers often purchase cushions to sit on in their trucks.

What is happening?

The pain that we feel when we sit on a firm, flat surface for long periods of time is due to a buildup of pressure right under our bony prominences. The most common bones are our “sitting bones,” the ischial tuberosities (ITs). As well, we often slouch and can sit right on our sacrum and/or coccygeal bone.

If we do nothing to protect those bony areas pressure builds up, cutting off blood supply, oxygen, and nutrient delivery to that area, leaving the skin and tissue between the seat surface and the bony prominence susceptible to ischemia. As we start to feel our bottom go numb, we begin to move and fidget, trying to relieve the discomfort or numbness.

What about our clients? Can they all move around to relieve this discomfort?  Or, do they even have the sensation to know that they need to move around?

We prescribe our clients a cushion to help assist with pressure relief, but do we understand what that cushion is doing?  It is important to understand the design and theory of how a cushion works to ensure it is the right type of cushion for your client.  If we are looking at a cushion for skin protection, we are looking at cushions to increase surface contact area.

Increasing Surface Contact Area:

We have to step back into our physics course to first understand.  Pressure is equal to Force over Area: P=F/A. Pressure can never truly be eliminated, but it can be redistributed to greater surface areas to produce less pressure. So, our goal should be pressure redistribution over the greatest surface area rather than only through small surface areas that would increase pressure.



How do we redistribute pressure in a skin protection wheelchair cushion?

We know now that we want to increase the surface area that the client contacts when sitting on a cushion. Pressure distribution can be accomplished in one of two cushion designs:

  •          Immersion
  •          Offloading

Next week we will begin our discussion on what these two design principles are and how they work.

Ana Endsjo, MOTR/L, Clinical Education Manager LTC Division Business Region Americas and Rachel Fabiniak, Clinical Education Australia/New Zealand


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