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 resolutionSENSE 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’
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)
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 = VB Let volume of displaced liquid = VL Let density of body = rhoB Let 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
Technology Explained (cont’d) ADJUSTABLEFits specific seating needs and unique body shapes LIGHTWEIGHTEasy to handle and carry, at just 4.6 lbs. /2kg. WASHABLECushion can be easily cleaned with soap and water. Cover is machine washable REPAIRABLENeoprene rubber cushion can be patched or repaired to extend use. VENTILATEDSeparate 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
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.
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.varilite.com www.ottobockus.com www.ottobockus.com www.plus2physics.com www.plus2physics.com www.roho.com www.roho.com www.starcushion.com www.starcushion.com www.systam.com www.systam.com www.columbianchemicals.com www.columbianchemicals.com JPO – Journal of Prosthetics and Orthotics Medical Design New – Sept/Oct 2001 Vibrating powder beds: a comparison of experimental and Distinct Element Method simulated data. A.J. Matchett. Powder Technology, 1999. Efficient Computation of Particle Motions in Discrete Element Modeling of 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