Design Alternatives

Patient Positioning AidE. Vargas, E. Kordeih, M. Britan

December 2, 2005

Outline

Brief Background Patient Specifications MRI Machine

Dimensions Applications

Design Alternatives Our Design Decision Future Direction References / Acknowledgements

Patient Specifications Bruce

Renal failure, manual wheelchair Joan

Heart failure, old, weak, hard of hearing Lloyd

Type II Diabetes, overweight Sophia

On heparin, limited right arm function, uses a cane Arnold

Parkinson’s, Diabetes, suffers from slight to moderate tremors

Dave Limited use to right arm and leg, may use a scooter.

Imaging: MRI Machine Phillips Achieva 3.0T

Sets the standard in comfort and image quality Provides strength through partnership with other coil

manufacturers Complements SENSE™ functionality for super-fast

imaging and exceptional resolution

Dimensions: Bed: 8’ L x 4’ W x 2” H Current pad: 2” thick (all around) Contour: 1.5” dip in center in ‘bed-frame’

MRI Procedure

How does it work?

MRI Applications

Design Alternatives

#1 - Bead filled mattress (original idea)

#2 - Star / ROHO Cushion

#3 – Otto Bach Cloud

#4 – Varilite ‘Pro-Form’ Concept

Design Alternative #1

Protocol for Bead Filled Mattress: Initially filled with air Patient lays down Beads contour body Deflation occurs Contour stays as a solid entity Clinician allows air back into the system Ready for the next patient

Bead Filled Mattress

What kind of beads? (material, size)

Covering? (Softness, elongation, tension, strength)

Encapsulation? (Grid blocking the inlet/out let of air)

Beads

Purpose of beads

Vibrations damper Dissipate excess energy Rapid response

Provide rigid support High surface friction High resilience characteristics

Purpose of Covering

Create tension Squeeze beads together High surface friction

Provide system/patient barrier Externally pleasant to touch Impermeable to fluids

Cover Naugahyde Darlex Knit

Water resistant Impermeable to air

Polar Fleece Rubatex – ‘Scuba Gear’ Vinyl

Assortment of Colors

Encapsulation

Purpose Prevent the beads from entering the tubes

Cylindrical cap at end of the inlet/out tube High surface area Plastic or strong polymer

Pros and Cons Pros:

Not extremely expensive. Imaging compatible. Retains shape and fixed positioning of any patient. Can absorb minimal amount of unavoidable

movement

Cons: Encapsulation of beads Method of suction Long tubing Extra stress on frightened patients

Design Alternative #2 Star / ROHO Cushion Concept

Synthesis of Floatation Technology (SOFT) Robert H. Graebe, the inventor of the ROHO

cushions Uses the principle of Flotation

Archimedes' Principle The surface forces it to behave the way

seawater envelops and supports a sea mammal Floatation is designed on the concept that

blood flow is primarily compromised as a function of deformation of the vascular bed. In total immersion, i.e., scuba divers.

Principles of Floatation F    =    hdg . A            [where A = base area]

      =    (Ah). d . g      =    V . d . g            [where V is the immersed volume]      =    m/g[where m' is the mass of the displaced liquid]

The upthrust is thus the weight of the displaced liquid..

Archimedes' Principle states that any body partly or wholly immersed in a liquid experiences an upthrust which is equal to the weight of the liquid displaced.

Let volume of body = VBLet volume of displaced liquid = VLLet density of body = rhoBLet density of liquid = rhoL – in our case air

Stability of Floatation

Buoyant force acts on the object at the center of gravity of displaced liquid

Star / ROHO (cont’d)

Technology Explained

Technology Explained (cont’d)

ADJUSTABLE Fits specific seating needs and unique body shapes

LIGHTWEIGHT Easy to handle and carry, at just 4.6 lbs. /2kg.

WASHABLE Cushion can be easily cleaned with soap and water. Cover is machine washable

REPAIRABLE Neoprene rubber cushion can be patched or repaired to extend use.

VENTILATED Separate air cells allow air circulation to reach the surface of skin and provide a cooling environment.

Features and benefits

Material Properties Neoprene Rubber

Physical Properties

NEOPRENE is a synthetic rubber material designed to act flexibly, durably, and to resist breakdown by water. It is form fitting and resilient. Because air and water become isolated in its unique molecular structure, Neoprene is temperately stable. The many uses of Neoprene include: wet suits, waders, insulated can holders, sports gloves, mouse pads, pet collars, elbow and knee pads, orthopedic braces, tack gear.

Pros and Cons

Pros Easy of use Uses Air instead of

water Custom contour all

times Normal body or

abnormal body shape

Equal pressure throughout the contact area

No power pump need Allows blood flow

Cons Leakage Needs proper inflation

Prices of Neoprene Rubber

 1-10

Sheets11-15 Sheets

16-25 Sheets

26-99 Sheets

1.5 mm $75.60 $37.80 $28.68 $25.92

2 mm $75.60 $37.80 $28.68 $25.92

3 mm $86.40 $43.20 $33.88 $28.80

4 mm $97.20 $48.60 $38.35 $32.40

5 mm $113.40 $51.03 $43.88 $37.80

6 mm $124.20 $62.10 $49.86 $41.40

Full Neoprene Sheets (51" x 83")

Design Alternative #3

Otto Bock – The Cloud The design / concept

The Cloud Benefits:

Produces clinically acceptable levels of pressure distribution.

Eliminates the risk of bottoming out and the potential for catastrophic failures due to punctures or leak.

Easy to use. No need to frequently check air fill levels or fluid position.

Easily modifies to individual's requirements for a customized fit.

Highly stable.

Disadvantages – The CLOUD

Self corrects to automatically and quickly adjust to the dynamic conditions Thus, does not have fixed posture

positioning. Requires a knowledgeable technician,

clinician, and/or therapist.

Design Alternative #4

Varilite ProForm NX An easy-to-customize,

off-the-shelf product. Original concept: Seating

Cushion Expand it to a larger

size: mattress

Air-Foam Flotation Cushion Designed for pelvic obliquities and other

asymmetrical conditions. Air-Foam Flotation cushion contains two self-

inlfating, independently-adjustable chambers (patent pending).

Adjustments are made using two-way air valves that release air to immerse the user in the foam.

The foam contours to the user and the user’s weight is distributed over the surface of the cushion.

ProForm NX is also available in a single chamber configuration.

Anaylsis – ProForm NX

Pros Fixed posture Comfortable Easy-to-use Patient specific No pump necessary Inexpensive MRI Safe

Cons For efficient

positioning may require 6-10 air valves.

Which One is Best?

RERC 2005-2006 Aim: Versatile, low-cost, easy-to-adjust

patient positioning aid that works with a range of examination table…and meets the customer needs.

Which One is Best?Customer Needs Bruce

Renal failure, manual wheelchair Joan

Heart failure, old, weak, hard of hearing Lloyd

Type II Diabetes, overweight Sophia

On heparin, limited right arm function, uses a cane Arnold

Parkinson’s, Diabetes, suffers from slight to moderate tremors

Dave Limited use to right arm and leg, may use a scooter.

Which One is Best?

Our Decision: ProFormNX

Integrates both air and foam. Requires no true expertise in air

quantity. Will never bottom out Durable (up to 5 years)

Meets our RERC 2005-2006 aim!!!

Our Design - Envisioned

Contoured platform Eliminate contour via

a solid wedge. Mattress topper will

lay flat. Thus can go on

most, if not all imaging tables.

Abide by the conditions set by the MRI machine

Future Direction Decisions must be made:

Foam Coverings Type of air valves Sizes of wedges using the same

technology.

References www.varilite.com www.ottobockus.com www.plus2physics.com www.roho.com www.starcushion.com www.systam.com www.columbianchemicals.com JPO – Journal of Prosthetics and Orthotics Medical Design New – Sept/Oct 2001 Vibrating powder beds: a comparison of experimental and

DistinctElement Method simulated data. A.J. Matchett. Powder Technology, 1999.

Efficient Computation of Particle Motions in Discrete Element Modelingof Particle Damping, Michael Yu Wang.

Acknowledgements

Dr. Strey – our advisor Dr. Wagshul – Radiology Department Rabson Rehab Sales

David Rabbiner Tom Sonntag

BioDynamics Ltd Raul Vargas

Thank You.

Any questions?