Wheelchair Seating - Policy Article

**NON-MEDICAL NECESSITY COVERAGE AND PAYMENT RULES:**  
For any item to be covered by Medicare, it must 1) be eligible for a defined
Medicare benefit category, 2) be reasonable and necessary for the diagnosis or
treatment of illness or injury or to improve the functioning of a malformed
body member, and 3) meet all other applicable Medicare statutory and
regulatory requirements. Information provided in this policy article relates
to determinations other than those based on Social Security Act 1862(a)(1)(A)
provisions (i.e. "reasonable and necessary").  
  
There is no separate payment for a solid insert (E0992) (see definition in
Coding Guidelines) that is used with a seat or back cushion because a solid
base is included in the allowance for a wheelchair seat or back cushion.  
  
There is no separate payment for mounting hardware for a seat or back cushion.  
  
There is no separate payment for a wheelchair seat or back cushion when it is
used with a rollabout chair (E1031).  
  
 **REQUIREMENTS FOR SPECIFIC DMEPOS ITEMS PURSUANT TO Final Rule 1713 (84 Fed.
Reg Vol 217)**

Final Rule 1713 (84 Fed. Reg Vol 217) requires a face-to-face encounter and a
Written Order Prior to Delivery (WOPD) for specified HCPCS codes. CMS and the
DME MACs provide a list of the specified codes, which is periodically updated.
The required Face-to-Face Encounter and Written Order Prior to Delivery List
is available [here](https://www.cms.gov/Research-Statistics-Data-and-
Systems/Monitoring-Programs/Medicare-FFS-Compliance-Programs/Medical-
Review/FacetoFaceEncounterRequirementforCertainDurableMedicalEquipment).

Claims for the specified items subject to Final Rule 1713 (84 Fed. Reg Vol
217) that do not meet the face-to-face encounter and WOPD requirements
specified in the LCD-related Standard Documentation Requirements Article
(A55426) will be denied as not reasonable and necessary.

If a supplier delivers an item prior to receipt of a WOPD, it will be denied
as not reasonable and necessary. If the WOPD is not obtained prior to
delivery, payment will not be made for that item even if a WOPD is
subsequently obtained by the supplier. If a similar item is subsequently
provided by an unrelated supplier who has obtained a WOPD, it will be eligible
for coverage.  
  

**POLICY SPECIFIC DOCUMENTATION REQUIREMENTS**  
  
In addition to policy specific documentation requirements, there are general
documentation requirements that are applicable to all DMEPOS policies. These
general requirements are located in the DOCUMENTATION REQUIREMENTS section of
the LCD.  
  
Refer to the LCD-related Standard Documentation Requirements article, located
at the bottom of this Policy Article under the Related Local Coverage
Documents section for additional information regarding GENERAL DOCUMENTATION
REQUIREMENTS and the POLICY SPECIFIC DOCUMENTATION REQUIREMENTS discussed
below.  

SPECIALTY EVALUATION:

The specialty evaluation (also known as a comprehensive written evaluation)
provides detailed information explaining why a prefabricated seating system is
not sufficient to meet the beneficiary's seating and positioning needs. There
must be a written report of this evaluation available on request. The PT, OT,
or practitioner who performs the specialty evaluation may have no financial
relationship with the supplier. (Exception: If the supplier is owned by a
hospital, the PT, OT, or practitioner working in the inpatient or outpatient
hospital setting may perform the specialty evaluation.)

  
MODIFIERS  
KX MODIFIER:  
  
For a skin protection seat cushion (E2603, E2604, E2622, E2623), a KX modifier
must be added to the code only if one of the following criteria (a), (b), or
(c) is met:

  1. There is a past history of, or current, pressure ulcer in the area of contact with the seating surface (refer to the Group 1 codes in the ICD-10 code list section); or

  2. There is absent or impaired sensation in the area of contact with the seating surface due to one of the diagnoses listed as a covered diagnosis in the Group 2 ICD-10 code list section; or

  3. There is an inability to carry out a functional weight shift due to one of the diagnoses listed as a covered diagnosis in the Group 2 ICD-10 code list section.

For a positioning seat cushion (E2605, E2606), positioning back cushion
(E2613, E2614, E2615, E2616, E2620, E2621), or positioning accessory (E0953,
E0956, E0957, E0960), a KX modifier must be added to the code only if the
beneficiary has significant postural asymmetries due to one of the diagnoses
listed as a covered diagnosis in Group 2 or Group 3 of the ICD-10 code list
section.  
  
For a headrest (E0955), a KX modifier must be added to the code only if one of
the coverage criteria specified in the Coverage Indications, Limitations
and/or Medical Necessity section of the related LCD has been met.  
  
For a combination skin protection and positioning seat cushion (E2607, E2608,
E2624, E2625), a KX modifier must be added to the code only if criterion (a)
or (b) or (c) is met and criterion (d) is met:

  1. There is a past history of, or current, pressure ulcer in the area of contact with the seating surface (refer to the Group 1 codes in the ICD-10 code list section); or

  2. There is absent or impaired sensation in the area of contact with the seating surface due to one of the diagnoses listed as a covered diagnosis for skin protection cushions (refer to the Group 2 codes in the ICD-10 code list section); or

  3. There is an inability to carry out a functional weight shift due one of the diagnoses listed as a covered diagnosis for skin protection cushions (refer to the Group 2 codes in the ICD-10 code list section); and

  4. The beneficiary has significant postural asymmetries due to one of the diagnoses listed as a covered diagnosis for positioning cushions (refer to the Group 2 and Group 3 codes in the ICD-10 code list section).

For a custom fabricated seat or back cushion (E2609, E2617), a KX modifier
must be added to the code only if criterion (a) is met and criterion (b), (c),
or (d) is met:

  1. For E2609 or E2617, there is a comprehensive written evaluation by a licensed/certified medical professional, such as a PT or OT (who has no financial relationship with the supplier) which explains why a prefabricated seating system is not sufficient to meet the beneficiary's seating and positioning needs; and

  2. For E2609, there is a past history of, or current, pressure ulcer in the area of contact with the seating surface; or

  3. For E2609, there is absent or impaired sensation in the area of contact with the seating surface or an inability to carry out a functional weight shift due to one of the diagnoses listed as a covered diagnosis for skin protection cushions (refer to the ICD-10 code list section); or

  4. For E2609 or E2617, the beneficiary has significant postural asymmetries due to one of the diagnoses listed as a covered diagnosis for positioning cushions (refer to the ICD-10 code list section).

In addition to meeting the specific requirements listed above, for all seat
and back cushions and positioning accessories, the KX modifier must be added
to the code only if the item is being used with a wheelchair that meets
coverage criteria specified in the Manual Wheelchair Bases or Power Mobility
Devices LCD.  
  
GA, GY, AND GZ MODIFIERS:  
  
For a cushion or positioning accessory that is used with a power mobility
device (PMD), if the requirements related to a standard written order (SWO)
for the PMD base and face-to-face encounter in the Power Mobility Devices
Policy Article have not been met, the GY modifier must be added to the codes
for all items.  
  
For items provided with a manual wheelchair or power mobility device, if it is
only needed for mobility outside the home, the GY modifier must be added to
the codes for all items.  
  
In all of the situations above describing use of the KX modifier, if all of
the specific coverage criteria have not been met or if the wheelchair that it
is being used with does not meet the coverage criteria in the Manual
Wheelchair Bases or Power Mobility Devices LCD, the GA or GZ modifier must be
added to a claim line for the seat or back cushion or positioning accessory.  
  
When there is an expectation of a medical necessity denial, suppliers must
enter the GA modifier on the claim line if they have obtained a properly
executed Advance Beneficiary Notice (ABN) or the GZ modifier if they have not
obtained a valid ABN.  
  
If the GY modifier is used, the KX, GA, and GZ modifiers should not be used.  
  
Claim lines billed without a GA, GY, GZ, or KX modifier will be rejected as
missing information.  
  
Miscellaneous  
  
When billing for a custom fabricated cushion (E2609, E2617), the claim must
include the manufacturer and model name/ number of the product (if
applicable), or if not, a detailed description of the product that was
provided.  
  
Refer to the Supplier Manual for additional information on documentation
requirements.  
  
 **CODING GUIDELINES:**  
  
The following definitions of seat cushions include results of simulation
testing or human subject testing. See the Testing Methodologies section for
technical information about the required testing.  
  
A general use seat cushion (E2601, E2602) is a prefabricated cushion, which
has the following characteristics:

  1. It has the following minimum performance characteristics: 
    1. Simulation tests demonstrate a loaded contour depth of at least 25mm with an overload deflection of at least 5 mm, or

    2. Human subject tests demonstrate an average peak pressure index that is less than 125% of that of a standard reference cushion within the area of the ischial tuberosities and sacrum/coccyx; and

  2. Following testing simulating 12 months of use: 
    1. Simulation tests demonstrate an overload deflection of at least 5 mm, or

    2. Human subject tests demonstrate an average peak pressure index that is less than 125% of those of a standard reference cushion within the area of the ischial tuberosities and sacrum/coccyx; and

  3. It has a removable vapor permeable or waterproof cover or it has a waterproof surface; and

  4. The cushion and cover meet the minimum standards of the California Bulletin 117, California Bulletin 133, or equivalent (such as standards established by the American Society for Testing and Materials (ASTM), the Environmental Protection Agency (EPA), or other national or international standards agencies), for flame resistance; and

  5. It has a permanent label indicating the model and the manufacturer; and

  6. It has a warranty that provides for repair or full replacement if manufacturing defects are identified or the surface does not remain intact due to normal wear within 12 months.



A nonadjustable skin protection seat cushion (E2603, E2604) is a prefabricated
cushion, which has the following characteristics:

  1. It has the following minimum performance characteristics: 
    1. Simulation tests demonstrate a loaded contour depth of at least 40 mm with an overload deflection of at least 5 mm, or

    2. Human subject tests demonstrate an average peak pressure index that is less than 85% of that of a standard reference cushion within the area of the ischial tuberosities and sacrum/coccyx; and

  2. Following testing simulating 18 months of use: 
    1. Simulation tests demonstrate an overload deflection of at least 5 mm, or

    2. Human subject tests demonstrate an average peak pressure index that is less than 85% of those of a standard reference cushion within the area of the ischial tuberosities and sacrum/coccyx; and

  3. It has a removable vapor permeable or waterproof cover or it has a waterproof surface; and

  4. The cushion and cover meet the minimum standards of the California Bulletin 117, California Bulletin 133, or equivalent (such as standards established by the ASTM, the EPA, or other national or international standards agencies), for flame resistance; and

  5. It has a permanent label indicating the model and the manufacturer; and

  6. It has a warranty that provides for repair or full replacement if manufacturing defects are identified or the surface does not remain intact due to normal wear within 18 months.

  
An adjustable skin protection seat cushion (E2622, E2623) has all the
characteristics of a E2603 or E2604 cushion and is determined to be adjustable
by the PDAC.

A positioning seat cushion (E2605, E2606) is a prefabricated cushion that has
the following characteristics:

  1. It has the minimum structural features described in (a) or (b):

    1. The feature must be at least 25 mm in height in the pre-loaded state. It has two or more of the following: 
      1. A pre-ischial bar or ridge which is placed anterior to the ischial tuberosities and prevents forward migration of the pelvis,

      2. Two lateral pelvic supports which are placed posterior to the trochanters and are intended to maintain the pelvis in a centered position in the seat and/or provide lateral stability to the pelvis,

      3. A medial thigh support which is placed in contact with the adductor region of the thigh and provides the prescribed amount of abduction and prevents adduction of the thighs,

      4. Two lateral thigh supports which are placed anterior to the trochanters and provide lateral stability to the lower extremities and prevent unwanted abduction of the thighs.

    2. It has two or more air compartments located in areas which address postural asymmetries, each of which must have a cell height of at least 50 mm, must allow the user to add or remove air, and must have a valve which retains the desired air volume; and

  2. It has the following minimum performance characteristics:

    1. Simulation tests demonstrate a loaded contour depth of at least 25mm with an overload deflection of at least 5 mm, or

    2. Human subject tests demonstrate an average peak pressure index that is less than 125% of that of a standard reference cushion within the area of the ischial tuberosities and sacrum/coccyx; and

  3. Following testing simulating 18 months of use:

    1. Simulation tests demonstrate an overload deflection of at least 5 mm, or

    2. Human subject tests demonstrate an average peak pressure index that is less than 125% of those of a standard reference cushion within the area of the ischial tuberosities and sacrum/coccyx; and

  4. It has a removable vapor permeable or waterproof cover or it has a waterproof surface; and

  5. The cushion and cover meet the minimum standards of the California Bulletin 117, California Bulletin 133, or equivalent (such as standards established by the ASTM, the EPA, or other national or international standards agencies), for flame resistance; and

  6. It has a permanent label indicating the model and the manufacturer; and

  7. It has a warranty that provides for repair or full replacement if manufacturing defects are identified or the surface does not remain intact due to normal wear within 18 months.

A positioning cushion may have materials or components that can be added or
removed to help address orthopedic deformities or postural asymmetries. This
definition includes cushions which have a planar surface but have positioning
features within the cushion which are made of a firmer material than the
surface material.

A nonadjustable skin protection and positioning seat cushion (E2607, E2608) is
a prefabricated cushion which has the following characteristics:

  1. It has the minimum structural features described in (a) or (b):

    1. The feature must be at least 25 mm in height in the pre-loaded state. It has two or more of the following: 
      1. A pre-ischial bar or ridge which is placed anterior to the ischial tuberosities and prevents forward migration of the pelvis,

      2. Two lateral pelvic supports which are placed posterior to the trochanters and are intended to maintain the pelvis in a centered position in the seat and/or provide lateral stability to the pelvis,

      3. A medial thigh support which is placed in contact with the adductor region of the thigh and provides the prescribed amount of abduction and prevents adduction of the thighs,

      4. Two lateral thigh supports which are placed anterior to the trochanters and provide lateral stability to the lower extremities and prevent unwanted abduction of the thighs.

    2. It has two or more air compartments located in areas which address postural asymmetries, each of which must have a cell height of at least 50 mm, must allow the user to add or remove air, and must have a valve which retains the desired air volume; and

  2. It has the following minimum performance characteristics:

    1. Simulation tests demonstrate a loaded contour depth of at least 40mm with an overload deflection of at least 5 mm, or

    2. Human subject tests demonstrate an average peak pressure index that is less than 85% of that of a standard reference cushion within the area of the ischial tuberosities and sacrum/coccyx; and

  3. Following testing simulating 18 months of use:

    1. Simulation tests demonstrate an overload deflection of at least 5 mm, or

    2. Human subject tests demonstrate an average peak pressure index that is less than 85% of those of a standard reference cushion within the area of the ischial tuberosities and sacrum/coccyx; and

  4. It has a removable vapor permeable or waterproof cover or it has a waterproof surface; and

  5. The cushion and cover meet the minimum standards of the California Bulletin 117, California Bulletin 133, or equivalent (such as standards established by the ASTM, the EPA, or other national or international standards agencies), for flame resistance; and

  6. It has a permanent label indicating the model and the manufacturer; and

  7. It has a warranty that provides for repair or full replacement if manufacturing defects are identified or the surface does not remain intact due to normal wear within 18 months.

This definition includes cushions which have a planar surface but have
positioning features within the cushion which are made of a firmer material
than the surface material.

An adjustable skin protection and positioning seat cushion (E2624, E2625) has
all the characteristics of a E2607 or E2608 cushion and is determined to be
adjustable by the PDAC. The adjustability feature only relates to the skin
protection properties of the cushion.  
  
Wheelchair cushions containing a fluid medium (air, gas, liquid, or gel) that
have the capability for the immersion characteristics of the cushion to be
altered by addition or removal of fluid will be considered adjustable. The
adjustment may be in the manner of direct addition or removal of the fluid
(e.g. add or remove air) or indirectly by addition or removal of packets of
fluid.  
  
Adjustment applies to the skin protection portion of the cushion's function
only.  
  
All cushions are considered to be adjustable up to the point of delivery to
the beneficiary. Fitting of the cushion to the individual beneficiary may
involve various forms of adjustment. Adjustable as applied here, requires that
the procedure is capable of being performed by the beneficiary or caregiver
using items supplied at the time of initial issue of the device in response to
the beneficiary's need for more or less skin protection because of weight loss
or gain or muscle tone changes.  
  

A general use back cushion (E2611, E2612) is a prefabricated cushion, which
has the following characteristics:

  1. It is planar or contoured; and

  2. It has a removable vapor permeable or waterproof cover or it has a waterproof surface; and

  3. The cushion and cover meet the minimum standards of the California Bulletin 117, California Bulletin 133, or equivalent (such as standards established by the ASTM, the EPA, or other national or international standards agencies), for flame resistance; and

  4. It has a permanent label indicating the model and the manufacturer; and

  5. It has a warranty that provides for repair or full replacement if manufacturing defects are identified or the surface does not remain intact due to normal wear within 12 months.



A positioning back cushion (E2613, E2614, E2615, E2616, E2620, E2621) is a
prefabricated cushion which has the following characteristics:

  1. For codes E2613, E2614, E2615, E2616, there is at least 25 mm of posterior contour in the pre-loaded state. A posterior contour is a backward curve measured from a horizontal line in the midline of the cushion; and

  2. For posterior-lateral cushions (E2615, E2616) and for planar cushions with lateral supports (E2620, E2621), there is at least 75 mm of lateral contour in the pre-loaded state. A lateral contour is a backward curve measured from a horizontal line connecting the lateral extensions of the cushion; and

  3. For posterior pelvic cushions (E2613, E2614), there is mounting hardware that is adjustable for horizontal position, depth, and angle; and

  4. It has a removable vapor permeable or waterproof cover or it has a waterproof surface; and

  5. The cushion and cover meet the minimum standards of the California Bulletin 117, California Bulletin 133, or equivalent (such as standards established by the ASTM, the EPA, or other national or international standards agencies), for flame resistance; and

  6. It has a permanent label indicating the model and the manufacturer; and

  7. It has a warranty that provides for repair or full replacement if manufacturing defects are identified or the surface does not remain intact due to normal wear within 18 months.

  
Included in this definition are cushions which have a planar surface but have
positioning features within the cushion which are made of a firmer material
than the surface material.  
  
A positioning back cushion may have materials or components that may be added
or removed to help address orthopedic deformities or postural asymmetries.  
  
A custom fabricated seat cushion (E2609) and a custom fabricated back cushion
(E2617) are cushions that are individually made for a specific beneficiary
starting with basic materials including:

  1. liquid foam or a block of foam and

  2. sheets of fabric or liquid coating material.

The cushion must be fabricated using one or more of the following techniques
to capture the individual shape of the beneficiary:

  * molded-to-beneficiary-model technique;
  * direct molded-to-beneficiary technique;
  * CAD/CAM technology, which: 
    * allows for the use of direct digital scanning of the beneficiary or of a mold made directly from the beneficiary;
    * allows for direct milling of either (1) a beneficiary-specific model used to shape the cushion contour or (2) the cushion contours; or
  * detailed measurements of the beneficiary used to create a configured cushion.

The cushion must have structural features that significantly exceed the
minimum requirements for a seat or back positioning cushion. The cushion must
have a removable vapor permeable or waterproof cover or it must have a
waterproof surface. A custom fabricated cushion may include certain
prefabricated components (e.g., gel or multi-cellular air inserts); these
components must not be billed separately. If a custom fabricated seat and back
are integrated into a one-piece cushion, code as E2609 plus E2617.  
  
If foam-in-place or other material is used to fit a substantially
prefabricated cushion to an individual beneficiary, the cushion must be billed
as a prefabricated cushion, not custom fabricated.  
  
A powered wheelchair seat cushion (E2610) is a battery-powered, prefabricated
cushion in which an air pump provides either sequential inflation or deflation
of the air cells or a low interface pressure throughout the cushion. One type
of powered seat cushion is an alternating pressure cushion.  
  
Pediatric seating system codes E2291, E2292, E2293, E2294 may only be billed
with pediatric wheelchair base codes.  
  
A headrest extension (E0966) is a sling support for the head. Code E0955
describes any type of cushioned headrest.  
  
A headrest (E0955) describes any type of cushioned headrest which may contain
one or more cushions to position the head and fixed mounting hardware.  
  
Lateral positioning items are used to provide lateral thigh or knee support
(E0953) or lateral trunk or hip support (E0956). These are provided in a
variety of shapes and sizes to suit the needs of the user.  
  
The code for a seat or back cushion includes any rigid or semi-rigid base or
posterior panel, respectively, that is an integral part of the cushion.  
  
A solid insert is a separate rigid piece of wood or plastic which is inserted
in the cover of a cushion to provide additional support. If a supplier chooses
to bill separately for a solid insert used with a seat cushion use code E0992
whether it is a manual or a power wheelchair. Code A9900 must be used for a
solid insert used with a back cushion.  
  
A solid support base for a seat cushion is a rigid piece of plastic or other
material which is attached with hardware to the seat frame of a wheelchair in
place of a sling seat. A cushion is placed on top of the support base. Use
code E2231 for a solid support base that is used with a manual wheelchair. A
solid support base is included in the allowance for the power wheelchair
codes. There should be no separate billing with power wheelchairs.  
  
If a supplier chooses to bill separately for mounting hardware, either
nonadjustable or adjustable, for a seat or back cushion or solid support base,
code A9900 must be used.  
  
The only products which may be billed using codes E2601, E2602, E2603, E2604,
E2605, E2606, E2607, E2608, E2610, E2611, E2612, E2613, E2614, E2615, E2616,
E2620, E2621, and E2622, E2623, E2624, E2625 and the only brand name products
that may be billed using codes E2609 or E2617 are those products for which a
written coding verification review (CVR) has been made by the Pricing, Data
Analysis, and Coding (PDAC) contractor. Information concerning the
documentation that must be submitted to the PDAC for a written CVR can be
found on the PDAC web site or by contacting the PDAC. A Product Classification
List (PCL) with products which have received a written CVR can be found on the
PDAC web site.  
  
If the prefabricated seat cushion, prefabricated back cushion, or a brand name
custom fabricated seat or back cushion has not received a written CVR from the
PDAC or if the PDAC has reviewed and determined that the product does not meet
the criteria for the code, then it must be billed with code K0669.

If a product is billed to Medicare using one of the HCPCS codes that requires
written CVR, but the product is not on the PCL for that particular HCPCS code,
then the claim line will be denied as incorrect coding.  
  
Pediatric size positioning accessories are billed with the codes described in
this policy. Codes E1025, E1026, E1027 (lateral thoracic and lateral/anterior
supports) are invalid for claim submission.  
  
Code E1028 (swingaway or removable mounting hardware upgrade) may be billed in
addition to codes E0953, E0955, E0956, E0957. It must not be billed in
addition to code E0960. It must not be used for mounting hardware related to a
wheelchair seat cushion or back cushion code.

Wheelchair seat and back cushion codes are all-inclusive. Use of HCPCS code
K0108 or any other HCPCS code to separately bill for added components such as
the foam blocks, gel packs, air cells, or equivalent material is incorrect
coding.

The right (RT) and left (LT) modifiers must be used when applicable. Effective
for claims with dates of service (DOS) on or after 3/1/2019, when the same
HCPCS code for bilateral items (left and right) is billed on the same DOS,
bill each item on two separate claim lines using the RT and LT modifiers and 1
unit of service (UOS) on each claim line. Do not use the RTLT modifier on the
same claim line and billed with 2 UOS. Claims billed without modifiers RT
and/or LT, or with RTLT on the same claim line and 2 UOS, will be rejected as
incorrect coding.

**TESTING METHODOLOGY**  
  
There are two testing methods that may be used to document wheelchair seat
cushion criteria: the simulation method and the human subject method.
Simulation tests are used to measure loaded contour depth and bottoming out.
Human subject tests are used to measure peak interface pressure.  
  
Simulation Test  
  
Simulation tests measure loaded contour depth and bottoming out. They use
standardized models of the human buttocks known as cushion-loading indenters
(CLIs). There are two CLIs that are used for simulation testing, a 25 mm CLI
and a 40 mm CLI. Specific design features of acceptable CLIs can be found on
the PDAC web site.  
  
Test method for determining 25 mm and 40 mm of contour depth:

  1. Place the test cushion on a flat, horizontal surface. Cushions with curved bases must be stable during contour measurement testing.

  2. Align the CLI so that it is centered from the sides of the cushion and so that the ischial tuberosities of the models are 11-15 cm from the rear edge of the cushion. The ischial tuberosity portion of the CLI should be aligned with the analogous portion of the test cushion.

  3. Load the CLI to 140 Newtons (31 pounds) & wait 5 minutes.

  4. Contact of the lateral buttons with the cushion indicates that the cushion has contoured to 25 or 40 mm depending on the CLI used - i.e., that it has passed the test for that trial.

  5. Repeat the test two times waiting 5 minutes between trials.

  
A cushion must pass the respective contour test during all trials to meet the
minimum criteria specified in the cushion definition section.  
  
Overload test method for measuring bottoming out:

  1. Record the height of the CLI from the horizontal surface at the end of the loaded contour depth test described above.

  2. Add 47 Newtons (10 pounds) to the CLI and record the height from the horizontal surface after 1 minute.

  3. Subtract the height at overload (#2) from the height at standard load (#1).

  4. Round the value in #3 to the nearest 5mm.

  5. Remove the overload weight and repeat the test twice, waiting 5 minutes between tests and measuring the height in #1 and #2 each time.

  6. Determine the median of the three values recorded in #4. This is the "overload deflection".

If the overload deflection is greater than or equal to 5mm, then the cushion
is determined not to have bottomed out during the test.  
  
Simulated use testing:  
  
There must be simulation of 12 or 18 months of use of the cushion (depending
on the cushion type - see Definitions section). Following simulated use, the
measurements for loaded contour depth and overload as described above must be
repeated.  
  
Test report:  
  
There must be a report of the tests which includes:

  1. The name and address of the facility performing the tests and the date(s) of the tests; and

  2. The manufacturer and brand name/number of the test cushion; and

  3. The weight of the cushion to the nearest 250 gm; and

  4. The width and length of the cushion; and

  5. The temperature and relative humidity of the room where the tests are conducted; and

  6. Identification of which CLI was used (25 mm or 40mm); and

  7. The results of the three loaded contour depth tests and the overload deflection test prior to simulated used testing; and

  8. A description of the method used to simulate cushion use; and

  9. A statement specifying the number of months of use that were simulated; and

  10. Measurements as described in #7 obtained after simulated use testing; and

  11. A statement attesting that the testing methodology described in this policy was followed; and

  12. The printed name and signature of the person performing or supervising the tests and the signature date.

  
Human Subject Tests  
  
The ability to demonstrate that there is an important reduction in interface
pressure in comparison with a standard reference cushion when tested with
human subjects is the basis for this approach. Human subject tests must be
performed by an entity that has received human subject testing approval from
an Institutional Review Board approved by the US Department of Health and
Human Services. Ten (10) wheelchair users must be studied, at least five of
which must be clinically insensate on the body surface contacting the cushion.  
  
Interface pressure measurements are taken with each subject seated on the
cushion being tested as well as on a standardized reference cushion (see
below). The measurements are obtained with a transducer placed on top of the
cushion. Subjects must be seated on the cushion and interface pressure
transducer for at least 60 seconds before data is collected. The subject
should be positioned in their typical posture as determined by query and
independent facility judgment. Three measurements are taken on each subject on
each cushion separated by a complete unloading of the cushion for at least 60
seconds.  
  
The standard reference cushion must be an uncovered 75 mm ( 5mm) thick high
resiliency foam with a rated 25% indentation force deflection (IFD) equal to
45 pounds (density range of 2.6-2.9 pounds/cubic ft and IFD range of 40-49
pounds).  
  
There must be a report of the tests which includes:

  1. The name and address of the facility performing the tests and the date(s) of the tests; and

  2. The manufacturer and brand name/number of the test cushion; and

  3. Information about the interface pressure measurement device utilized:

    1. Manufacturer and brand name

    2. Date of most recent calibration

    3. Percent error of measurement at 50 and 100 mm Hg pressure; and

  4. Actual 25% IFD and density of the reference cushion (obtained from the foam manufacturer or supplier) and actual thickness of the reference cushion; and

  5. Information on each subject (coding subjects to preserve confidentiality) including:

    1. Age

    2. Height

    3. Weight

    4. Disability

    5. Buttocks sensation status; and

  6. Interface pressure measurements for each subject on the test cushion and on the reference cushion:

    1. If the transducer covers the entire seating area, the entire map showing the pressure in each cell must be submitted. The anatomical locations (as determined by palpation) of the right and left ischial tuberosities and the sacrum/coccyx must be identified on each map. (Data can be submitted as a hard copy map or utilizing the device software.) or,

    2. If the transducer only covers a portion of the seat surface, measurements must be taken at the following three locations (as determined by palpation): right and left ischial tuberosities and sacrum/coccyx. The report must identify the anatomical location of each set of measurements. The report must list the pressure in each cell at each specified location. The values for the three locations are considered a single test; and

  7. The Peak Pressure Index (PPI) for each subject on the test cushion and on the reference cushion. The PPI is determined as follows:

    1. For each test, identify the cell in the sacro-ischial zone with the highest pressure;

    2. Determine the greatest sum of pressures in the identified cell and the adjacent cells in a 9-10 square centimeter area. If there are multiple cells with the same "highest pressure", consider all of them in the determination of the "greatest sum". [Note: A 3 cm by 3 cm square or a 3.5 cm diameter circular area are examples of a 9-10 sq cm area. For example, if using an interface pressure sensing array with a cell size of 1 sq cm, 9 cells (a 3 by 3 array) are used and if using a sensing array with a cell size of 2.5 sq cm, 4 cells (a 2 by 2 array) are used.];

    3. For each test, calculate the average of the cells with the greatest sum of pressures;

    4. Calculate the average of the results obtained in step (c) for the 3 tests on the test cushion and the 3 tests on the reference cushion. These values are the PPIs for the subject on each cushion; and

  8. A statement attesting that the testing methodology described in this policy was followed; and

  9. The printed name and signature of the person performing or supervising the tests and the signature date.

  
To determine if the minimum performance characteristics specified in the
Definitions section for a particular type of cushion have been met, calculate
the average PPI for the 10 subjects on the test cushion and the average PPI
for the 10 subjects on the reference cushion. Divide the average PPI on the
test cushion by the average PPI on the reference cushion and multiply the
value by 100 to give the percentage comparison of Peak Pressure Indexes. If
the comparative pressures are less than the specified values (125% or 85%
depending on the cushion), then the minimum performance characteristics with
respect to pressure have been met.