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 usually over 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-blanchable redness of localised area, usually over a bony prominence. NPUAP-EPUAP
SEVERITY OF PRESSURE ULCERS 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
SEVERITY OF PRESSURE ULCERS GRADE III: Full Thickness Skin Loss Full thickness tissue loss. Subcutaneous fat may be visible but bone, tendon or muscle are not exposed. NPUAP-EPUAP
SEVERITY OF PRESSURE ULCERS GRADE IV: Full Thickness Tissue Loss Full thickness tissue loss with exposed bone, tendon or muscle. NPUAP-EPUAP
PRESSURE ULCER DEVELOPMENT MOBILITY ACTIVITY PRESSURE SENSORY PERCEPTION EXTRINSIC FACTORS INTRINSIC FACTORS TISSUE TOLERANCE PRESSURE ULCER DEVELOPMENT
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 Arms (2%) Back (4%) Feet (19%) Thighs & Buttocks (75%)
PRESCRIBING FOR PRESSURE USER CHARACTERISTICS Goals TASK CHARACTERISTICS CUSHION CHARACTERISTICS
DESIGNING FOR PRESSURE CUSHION CHARACTERISTICS Redistribution of Pressure Management of Shear Forces Postural Support Management of Vibration and Shock Thermal Properties
DESIGNING FOR PRESSURE - MATERIALS POLYURETHANE FOAM (PU) Flexible, open-cell foam Quick recovery after compression Permeable
DESIGNING FOR PRESSURE - MATERIALS POLYETHYLENE FOAM 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
DESIGNING FOR PRESSURE - MATERIALS VISCO-ELASTIC FOAM Slow recovery after compression Can dampen vibration and shock Contours to shapes more closely than standard PU foams Hardness sensitive to temperature and humidity
DESIGNING FOR PRESSURE - MATERIALS FLUIDS/GELS Liquid gels displace and conform to equalise pressure Baffles and compartments restrict flow The lower the viscosity the greater the shock absorbency
DESIGNING FOR PRESSURE - MATERIALS AIR Air moves between cells equalising internal pressure Compartments restrict movement to improve stability Set up and maintenance required
DESIGNING FOR PRESSURE - SHAPE CONTOURING Allows greater immersion and distributes pressure over a greater surface area Can improve dynamic stability
DESIGNING FOR PRESSURE - SHAPE SEGMENTATION Reduces surface tension and increases pressure redistribution Greater ability to move with the user reduces shear forces
DESIGNING FOR PRESSURE - SHAPE ANTI-THRUST Accommodates the Ischial Tuberosities Improves weight loading under the thighs Helps stabilise the pelvis Can prevent sliding forwards
DESIGNING FOR PRESSURE - SHAPE MODULARITY Allows standard products to be customised for individual clients Can cater for a range of pressure requirements and scenarios
FOAM Density Firmness Ability to return to original shape Slab Molded
SHAPE Pressure Management is dependent on distribution of weight and pressure off of the ischials and onto the lateral trochanter shelf & femurs
CUSHION DESIGN Immersion Maximizes surface contact area to reduce peak pressures. Pressure = Force/Area Off-Loading Transfers forces. away from the ischial tuberosities with greater weight bearing on the trochanters, hips and thighs. Envelopment Fluid sac completely surrounds the bony prominences, even during position changes.
SHEAR MANAGEMENT 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.
ASSESSMENT TOOLS
MAT EVALUATION MAT = Mechanical assessment tool 3 stages: 1. Assessment in existing seating system 2. Assessment in supine 3. Assessment in sitting
PRESSURE MAPPING AS AN ASSESSMENT TOOL Pressure = Force / Area Aim: to minimise peak pressures and maximise surface area Pressure gradients indicate the potential presence of shear forces
PRESSURE MAPPING How will your cushion map?
P R I N C I P L E S F O R SEATING & POSITIONING
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
SEATING & POSITIONING SEATING OBJECTIVES 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 & POSITIONING GUIDING PRINCIPLES 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.
SEATING & POSITIONING 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.
M A N A G E M E N T O F COMMON SEATING AND POSTURAL PROBLEMS
STABILITY 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.
POSTERIOR PELVIC TILT WITH KYPHOSIS CLINICAL PRESENTATION Cervical spine may hyper-extend to maintain a functional visual field Scapula may protrude posteriorly Flattened lumbar spine and increased thoracic kyphosis Tendency for pelvis to slide forwards Pelvis tilted posteriorly with the Anterior Superior Iliac Spine (ASIS) higher than the Posterior Superior Iliac Spine (PSIS)
POSTERIOR PELVIC TILT WITH KYPHOSIS FLEXIBLE POSTURE Consider anterior chest support Consider support for upper limbs Contoured cushion to help stabilise the pelvis in a neutral position Firm back support that stabilises from the PSIS up to slightly above the apex of the kyphotic curve Pelvic positioning belt beneath the ASIS
POSTERIOR PELVIC TILT WITH KYPHOSIS FIXED POSTURE Provide a contoured back support to match shape of spine 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 Contoured cushion to support the pelvis 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
ANTERIOR PELVIC TILT WITH HYPERLORDOSIS CLINICAL PRESENTATION Trunk often extended to compensate for instability from anterior pelvic tilt May present with shoulder retraction May present as exaggerated lumbar lordosis and result in decreased contact with the back support surface Pelvic to thigh angle less than 90 degrees Pelvis tilted anteriorly with ASIS lower than the PSIS
ANTERIOR PELVIC TILT WITH HYPERLORDOSIS FLEXIBLE POSTURE Consider anterior chest support Early use of powered seating to allow independent adjustment for comfort and/or function balance 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 lordosis
ANTERIOR PELVIC TILT WITH HYPERLORDOSIS FIXED POSTURE Angle and depth adjustable back support Angle rear of the seat lower than the front to balance trunk over the pelvis
PELVIC OBLIQUITY AND SCOLIOSIS CLINICAL PRESENTATION 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 Shoulder often elevated on the oblique side Increased pressure risk on oblique side One side of the pelvis is lower than the other
PELVIC OBLIQUITY AND SCOLIOSIS FLEXIBLE POSTURE Ensure lateral depth is deep enough to support the trunk Lateral supports 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 Lateral/hip supports If flexible, build up the cushion under the lowest ischial tuberosity to encourage a level pelvis
PELVIC OBLIQUITY AND SCOLIOSIS FIXED POSTURE 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 CLINICAL PRESENTATION Movement of the femur away from midline Can be unilateral or bilateral Lower extremities are separated further apart from neutral
HIP ABDUCTION FLEXIBLE POSTURE Try to align femurs in neutral using contoured cushion or distal lateral supports Contoured cushion to align lower extremities FIXED POSTURE Accommodate with custom contoured seating
HIP ADDUCTION CLINICAL PRESENTATION Movement of femurs toward midline Can be unilateral or bilateral
HIP ABDUCTION FLEXIBLE POSTURE Use seat rigidiser or solid seat pan Trial distal medial thigh support or contoured seating Contoured cushion to align lower extremities FIXED POSTURE Accommodate with custom contoured seating Cushion rigidiser contoured to eliminate hammock effect of sling upholstery
PELVIC ROTATION CLINICAL PRESENTATION One ASIS and therefore hip is further forward in the seat than the other One hip is abducted, the other adducted One knee may appear further forward
PELVIC ROTATION FLEXIBLE POSTURE In order to maintain head and shoulder in a neutral position for function, you may need to maintain some asymmetry in the pelvis Use a contoured cushion to align the pelvis in neutral and support lower extremity posture Use a pelvic positioning belt to bring hips back into alignment
PELVIC ROTATION FIXED POSTURE Accommodate limited hip flexion by opening seat to back angle Contoured back support rotated to accommodate any mild/moderate trunk rotation, support the spine and distribute pressure If present, measure the leg length difference Order cushion for longer leg length and specify amount to cut back on shorter side