PRESSURE & POSTURE IN WHEELCHAIR SEATING€¦ · Full thickness tissue loss. Subcutaneous fat may...

PRESSURE & POSTURE IN WHEELCHAIR SEATING

DEFINITION OF PRESSURE

Pressure = Force / Area

ANATOMY OF THE SKIN

Epidermis

Dermis

Subcutaneous Layer

EFFECTS OF PRESSURE

• Occludes capillaries

• Restricts flow of oxygen and vital nutrients

• Lymphatic drainage restricted

• Cell deformation under sustained pressure can also lead to cell death

DEFINITION OF PRESSURE ULCERS

“A pressure ulcer is localised injury to the skin and/or underlying tissue usuallyover a bony prominence, as a result of pressure, or pressure in combination with shear”

International NPUAP-EPUAP Pressure Ulcer Definition

SHEAR

• Forces parallel to the seating surface

• Often created by the effects of gravity

SEVERITY OF PRESSURE ULCERS

GRADE I: Nonblanchable Erythema

“Intact skin with non-blanchableredness of localised area, usually over a bony prominence.”

NPUAP-EPUAP


GRADE II: Partial Thickness Skin Loss

“Partial thickness loss of dermis presenting as a shallow open ulcer with a red pink wound bed, without slough…”

NPUAP-EPUAP


GRADE III: Full Thickness Skin Loss

“Full thickness tissue loss. Subcutaneous fat may be visible but bone, tendon or muscle are notexposed.”

NPUAP-EPUAP


GRADE IV: Full Thickness Tissue Loss

“Full thickness tissue loss with exposed bone, tendon or muscle.”

NPUAP-EPUAP

PRESSURE ULCER DEVELOPMENT

PRESSURE

MOBILITY

ACTIVITY

SENSORY PERCEPTION

TISSUETOLERANCE

PRESSURE ULCER

DEVELOPMENT

EXTRINSIC FACTORS

INTRINSIC FACTORS

EXTRINSIC FACTORS

• Localised Pressure

• Shear & Friction

• Poor Posture

• Time

• Temperature

• Moisture

INTRINSIC FACTORS

• Impaired Reaction to Pressure

• Restricted Movement

• Impaired Sensation

• Decreased Tissue Tolerance

• Heart Problems

• Vascular Disease

• Diabetes

• Serious Illness

• Old Age

• Incontinence

• Neurological Conditions

• Medication

PREVENTATIVE MEASURES

• Maintain regular changes in position and avoid positioning over areas of erythema whenever possible.

• Keep the skin clean and dry. Manage any incontinence issues.

• Maintain good nutrition.

• Use appropriate equipment where applicable.

P R I N C I P L E S O F

CUSHION DESIGN

PRESSURE DISTRIBUTION IN NEUTRAL SITTING

Feet (19%)

Arms (2%)

Back (4%)

Thighs & Buttocks (75%)

PRESCRIBING FOR PRESSURE

Goals

USER CHARACTERISTICS

TASKCHARACTERISTICS

CUSHIONCHARACTERISTICS

DESIGNING FOR PRESSURE

CUSHIONCHARACTERISTICS

• Redistribution of Pressure

• Management of Shear Forces

• Postural Support

• Management of Vibration and Shock

• Thermal Properties

DESIGNING FOR PRESSURE - MATERIALS

• Flexible, open-cell foam

• Quick recovery after compression

• Permeable

POLYURETHANE FOAM (PU)


• Rigid, light-weight, non-permeable, closed cell foam

• Shock absorbing properties

• Used in cushion bases to provide postural support in combination with a top conforming surface

POLYETHYLENEFOAM

• Slow recovery after compression

• Can dampen vibration and shock

• Contours to shapes more closely than standard PU foams

• Hardness sensitive to temperature and humidity


VISCO-ELASTIC FOAM


• ‘Liquid gels’ displace and conform to equalise pressure

• Baffles and compartments restrict flow

• The lower the viscosity the greater the shock absorbency

FLUIDS/GELS


• Air moves between cells equalising internal pressure

• Compartments restrict movement to improve stability

• Set up and maintenance required

AIR

DESIGNING FOR PRESSURE - SHAPE

• Allows greater immersion and distributes pressure over a greater surface area

• Can improve dynamic stability

CONTOURING


• Reduces surface tension and increases pressure redistribution

• Greater ability to move with the user –reduces shear forces

SEGMENTATION


• Accommodates the Ischial Tuberosities

• Improves weight loading under the thighs

• Helps stabilise the pelvis

• Can prevent sliding forwards

ANTI-THRUST


• Allows standard products to be customised for individual clients

• Can cater for a range of pressure requirements and scenarios

MODULARITY

• Density

• Firmness

• Ability to return to original shape

Slab Molded

FOAM

Pressure Management is

dependent on distribution of

weight and pressure off of the

ischials and onto the lateral

trochanter shelf & femurs

SHAPE

.

ImmersionMaximizes surface contact area to reduce peak pressures.Pressure = Force/Area

Off-LoadingTransfers forcesaway from the ischialtuberosities with greaterweight bearing on thetrochanters, hips andthighs.

EnvelopmentFluid sac completelysurrounds the bonyprominences, evenduring position changes.

CUSHION DESIGN

Static • Support surface contour that prevents sliding and downward migration of the pelvis.

Dynamic • Flow of materials reduces tension between bony prominences and tissues during functional activities, wheelchair propulsion, accommodates movement within a specific range.

Optimal shear reduction addresses both static and dynamic shear without compromising posture.

SHEAR MANAGEMENT

ASSESSMENT TOOLS

MAT = Mechanical assessment tool

3 stages:

1. Assessment in existing seating system

2. Assessment in supine

3. Assessment in sitting

MAT EVALUATION

PRESSURE MAPPING AS AN ASSESSMENT TOOL

• Aim: to minimise peak pressures and maximise surface area

• Pressure gradients indicate the potential presence of shear forces

Pressure = Force / Area

PRESSURE MAPPING

How will your cushion map?

P R I N C I P L E S F O R

SEATING & POSITIONING


Assist individuals in achieving their goals and aspirations, while respecting lifestyle,

function, posture and skin protection by providing simple, effective, and safe seating

solutions


• Facilitate postural stability while allowing purposeful movement .

• Accommodate 3-dimensional anatomical shapes, working to match contours for optimal support and pressure redistribution.

• Wherever possible, support postures from within the contours of the seating system. If needed, complement with additional external components.

SEATING OBJECTIVES


• A comprehensive evaluation, including a physical assessment in both supine and sitting, is the foundation of all effective seating solutions. Where possible, trial seating in static and dynamic situations.

• The position of the pelvis directly impacts the spine, which in turn influences the position of the head and extremities.

GUIDING PRINCIPLES


• Determining if a posture is fixed or flexible is important for selecting appropriate seating solutions.

• The effect that seated posture has on breathing and swallowing should be a primary concern.

GUIDING PRINCIPLES

M A N A G E M E N T O F

COMMON SEATING AND POSTURAL PROBLEMS

Pelvic Stability

Contouring of the pelvic well provides lateral trochanteric support and anterior/posterior pelvic stability, promoting spinal extension for improved upper extremity function, head control and physiological function.

Note: Back support must be addressed for complete postural and skin protection solution.

STABILITY

POSTERIOR PELVIC TILT WITH KYPHOSIS

Cervical spine may hyper-extend to maintain a functional visual field

Scapula may protrude posteriorly

Flattened lumbar spine and increased thoracic kyphosis

Pelvis tilted posteriorly with the Anterior Superior Iliac Spine (ASIS) higher than the Posterior Superior Iliac Spine (PSIS)

Tendency for pelvis to slide forwards

CLINICAL PRESENTATION


Consider anterior chest support

Consider support for upper limbs Firm back support that stabilises from the PSIS up to slightly above the apex of the kyphotic curve

Pelvic positioning belt beneath the ASIS

Contoured cushion to help stabilise the pelvis in a neutral position

FLEXIBLEPOSTURE


Consider utilising tilt to achieve a more upright position and improve functional visual field and head position

If spinal process or ribs are prominent increase backrest depth for greater immersion

For a unilateral limitation in hip flexion, modify the cushion to split the sagittal seat angle to accommodate and try to achieve a level pelvis

Contoured cushion to support the pelvis

FIXEDPOSTURE

Provide a contoured back support to match shape of spine

ANTERIOR PELVIC TILT WITH HYPERLORDOSIS

May present with shoulder retraction

Pelvic to thigh angle less than 90 degrees

May present as exaggerated lumbar lordosis and result in decreased contact with the back support surface

Pelvis tilted anteriorly with ASIS lower than the PSIS

Trunk often extended to compensate for instability from anterior pelvic tilt



Consider anterior chest support

Each client will differ in preference of sagittal seat and back support angles, especially those with Muscular Dystrophy and Spina Bifida

Assess small incremental changes to seat slope and angle of back support the move the pelvis and spine into a neutral orientation

Provide back support at level of PSIS to reduce lordosisEarly use of powered seating to allow

independent adjustment for comfort and/or function balance

FLEXIBLEPOSTURE


Angle and depth adjustable back support

FIXEDPOSTURE

Angle rear of the seat lower than the front to balance trunk over the pelvis

PELVIC OBLIQUITY AND SCOLIOSIS

Shoulder often elevated on the oblique side

Increased pressure risk on oblique side

One side of the pelvis is lower than the other

The obliquity is referred to by the lower side of the pelvis

The spine is influenced by the oblique pelvis, resulting in scoliosis.

The spinal curve will be convex on the oblique (lower) side of the pelvis



Lateral supports

Lateral/hip supports

FLEXIBLEPOSTURE

Ensure lateral depth is deep enough to support the trunk

Lateral trunk supports can be used to provide either 3 or 4 key points of control to support or minimise progression of scoliosis

Alternate approach – deep contoured back with lateral contour positioned to support the ribcage

If flexible, build up the cushion under the lowest ischial tuberosity to encourage a level pelvis


FIXEDPOSTURE

Ensure lateral depth is deep enough to support the trunk

Contoured back with integral lateral support

If fixed, build up support under the highest ischial tuberosity to increase weight bearing on high side

HIP ABDUCTION

Movement of the femur away from midline

Can be unilateral or bilateral

Lower extremities are separated further apart from neutral


HIP ABDUCTION

Try to align femurs in neutral using contoured cushion or distal lateral supports

FLEXIBLEPOSTURE

Contoured cushion to align lower extremities

Accommodate with custom contoured seating

FIXEDPOSTURE

HIP ADDUCTION

Movement of femurs toward midline

Can be unilateral or bilateral


HIP ABDUCTION

Use seat rigidiser or solid seat pan

Trial distal medial thigh support or contoured seating

FLEXIBLEPOSTURE

Contoured cushion to align lower extremities

Accommodate with custom contoured seating

FIXEDPOSTURE

Cushion rigidiser contoured to eliminate ‘hammock effect’ of sling upholstery

PELVIC ROTATION

One hip is abducted, the other adducted

One knee may appear further forward

One ASIS and therefore hip is further forward in the seat than the other


PELVIC ROTATION

Use a contoured cushion to align the pelvis in neutral and support lower extremity posture

FLEXIBLEPOSTURE

Use a pelvic positioning belt to bring hips back into alignment

In order to maintain head and shoulder in a neutral position for function, you may need to maintain some asymmetry in the pelvis

PELVIC ROTATION

FIXEDPOSTURE

Accommodate limited hip flexion by opening seat to back angle

If present, measure the leg length difference

Order cushion for longer leg length and specify amount to cut back on shorter side

Contoured back support rotated to accommodate any mild/moderate trunk rotation, support the spine and distribute pressure

PRESSURE & POSTURE IN WHEELCHAIR SEATING€¦ · Full thickness tissue loss. Subcutaneous fat may...

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