Let’s get it clear: What makes a good cushion? 7. Standard of evidence

Let’s get it clear: What makes a good cushion? 7. Standard of evidence

Are there any distinctions in between one cushion and the next and, if so, just how much difference is there? What do the values from cushion particular tests indicate for completion user? These stand questions, and are necessary when explaining to procurement departments that all cushions are not the same– even within the exact same classification (see below).

Figure 1. The stability report from Explore our data

Theres a variety of cushion qualities which we can measure, which are essential for the wellness of the customer. These consist of aspects such as pressure distribution, immersion, envelopment, stability, temperature guideline, wetness guideline, modifications with aging, amongst others. This builds an intricate photo of each cushion, and to assist in fact quantify these elements there are a number of tests covered by a variety of International standards within the ISO 16840 series.

In previous short articles in this series, we have actually taken a look at components of cushion design that affect a cushions properties for handling skin health and tissue stability, for offering postural assistance, and for aspects of functionality. This short article looks at some of the specific data that have been produced for a vast array of cushions, all of which develops that no 2 cushions are the very same, and that a cushion picked for a client needs to be selected around the particular qualities which match that private customers requirements.

Wheelchair and cushion details

The University of Pittsburghs Wheelchair & & Cushion Standards Group is using an NIDILRR1 grant to translate these ISO efficiency standards into a method that is easy to understand and gives suitable and practical recommendations which can be utilized by healthcare experts, manufacturers, wheelchair users, etc, to implement and call upon in everyday practice. The outcomes of their work to date can be discovered on their website.

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This website is an outstanding resource, with useful truth sheets on a range of topics, for instance, elements of wheelchair performance, in addition to on Cushion Performance Overview and a Cushion Performance Interpretation Guide. The latter covers 7 of the available tests, explaining the reason that each is utilized, a summary of the test (with images of the test set-up), the series of worths found throughout a variety of cushions, and a sign of the significance of being at one end or the other of a variety of values for that test.

If you turn to the Explore Our Data Tab, here you will find information for around 50 various cushions, measuring:

Loaded Contour Depth and Overload Deflection (ISO 16840-22 Clause 11): a test to assess a cushions capability to immerse the buttocks

Envelopment (ISO 16840-124): a test that characterizes a cushions ability to envelop and immerse the butts (information to be included quickly).

This report likewise shows the impacts of sped up aging (utilizing methodology from ISO 16840-63) including laundering, disinfection, sped up aging, and cyclic filling protocols on some of the cushions for various of the previous steps, along with.

Horizontal Stiffness (ISO 16840-22 Annex C): a test to evaluate a cushions action to minor horizontal movements in the forward direction.

Hysteresis (ISO 16840-22 Clause 14): a test to assess a cushions ability to supply assistance regularly during a cycle of filling and unloading.

Pressure Mapping (ISO 16840-63 Clause 14): a test that makes use of user interface pressure measurements to examine the magnitude and circulation of pressure on a crammed cushion.

Impact Damping (ISO 16840-22 Clause 9): a test to assess a cushions ability to decrease effect filling on tissues and help keep postural stability when performing jobs such as going off a kerb.

10% Force Deflection (ISO 16840-63 Clause 20): a test to assess a cushions capability to cushion or elastically deform by measuring the force required to produce a deflection of 10% of the cushion density.

Additional items can be found at www.beshealthcare.net. If you have an interest in getting more information on the subject, please contact barend@beshealthcare.net.


On this report, you can select tabs for the various tests which colour code the cushions by their CMS code. What is a CMS code I hear you ask– well, unlike the UK where we do not have codes, in the United States, the Centers for Medicare and Medicaid Services (CMS) have actually created codes which cover certain requirements which a cushion needs to satisfy for that code, and from that the reimbursement level it gets. The different codes cover cushions for: General Use; Positioning; Skin Protection; Skin Protection and Positioning; Adjustable Skin Protection; and Adjustable Skin Protection and Positioning.

A couple of the graphs are recreated here as Figures 1 and 2 showing the different efficiencies of the cushions tested against the criteria of stability and force deflection. Keep in mind that cushions M and AU, for instance, are at opposite extremes in Figure 1, whereas they have comparable worths in Figure 2. To use the information in a practical way, one needs to pick a step or measures that is/are proper for your clients needs.

At this stage, all the cushions have been blinded while approval is sought from the manufacturers to recognize their cushions, but why not ask your supplier which cushion letter represents their tested cushion? The crucial thing to note is that the data are not pass/fail requirements, and do not point to one cushion always being better than another. For some clients it is important for them to have a cushion carrying out at one end of a scale, while for others it might be the opposite end.

Test information.

The National Institute on Disability, Independent Living, and Rehabilitation Research.
ISO 16840-2:2018 Determination of mechanical and physical qualities of seat cushions planned to handle tissue stability.
ISO 16840-6:2015 Simulated use and decision of the modifications in properties of seat cushions.
ISO 16840-12:2021 Apparatus and method for cushion envelopment screening.

The sped up aging protocols were then duplicated a 2nd time from which one can see which of the checked cushions saw their qualities alter the very first time round, and which ones changed again after the duplicated aging procedure.

Figure 2 The 10% Force Deflection report from Explore our data.


For all the tests, the values are offered contrast functions with those for a reference foam cushion comprised of a 3″ thick, high density polyurethane foam with a 25% IFD of 170 N and 65% IFD of 320 N. The reference foam cushion had a cover with a 2-way stretch nylon/spandex top and non-slip polyester bottom.

It is also interesting to keep in mind that normally the cushions do not group together by their CMS code: this raises the question regarding whether the bases for these codes have actually been set together with the most appropriate criteria. (The coding is based upon the Loaded Contour Depth test with added immersion and overload deflection requirements per code.) A minimum of these criteria are somewhat better than defining a cushion by what it is made from, or what it looks like, which has happened in some tendering processes in the UK.

Click to read more from the Lets get it clear series from Dr Barend ter Haar.

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Eventually, the Pitt group intends to bring all the information together, to occupy, in the Cushion Concierge page, cushion performance data resource, based on these ISO requirement tests. This resource can then be used to assist health care specialists transform the wheelchair cushion choice procedure, and advance evidence-based clinical practice.

Dr Barend ter Haar has actually been included in seating and mobility for over 30 years, including lecturing globally and developing international seating standards.

What do the worths from cushion particular tests indicate for the end user? On this report, you can pick tabs for the different tests which colour code the cushions by their CMS code. A couple of the charts are replicated here as Figures 1 and 2 showing the various efficiencies of the cushions tested versus the criteria of stability and force deflection. At this phase, all the cushions have been blinded while consent is looked for from the manufacturers to identify their cushions, but why not ask your provider which cushion letter represents their checked cushion? The important thing to note is that the data are not pass/fail requirements, and do not point to one cushion always being better than another.