Application of Biomechanical Principles to Wheelchair Transport Safety: What can be done today!

Size: px

Start display at page:

Download "Application of Biomechanical Principles to Wheelchair Transport Safety: What can be done today!"

Heather Lawrence
5 years ago
Views:

1 Application of Biomechanical Principles to Wheelchair Transport Safety: What can be done today! Douglas A. Hobson. Ph.D. Gina Bertocci, Ph.D. Rehabilitation Engineering Research Center Department of Rehabilitation Science and Technology School of Health and Rehabilitation Sciences University of Pittsburgh This presentation is intended for school-based therapists, rehabilitation engineers, seating and mobility clinicians, parents and wheelchair users who are attempting to improve the safety of persons seated in wheelchairs while travelling in motor vehicles.

2 Learning Objectives To learn how to enhance transport safety using today s tools, To become aware of the most critical safety concerns, To become more knowledgeable regarding pending industry solutions, To become aware of additional information sources

3 Orientation in the vehicle Forward facing- frontal crashes most common most practical and safe required in ADA* and FMVSS 22*-(school buses) Rearward facing- most safe, usually not practical Sideways facing-not recommended occupant and W/C least able to withstand frontal crash loads *ADA-Americans with Disabilities Act *FMVSS 22-Federal Motor Vehicle Safety Standard that regulates the design and safety of school buses.

4 Occupant Restraints Safety restraint* vs. postural support* must clearly distinguish between two objectives. Fit and comfort issues most vehicle mounted occupant restraints for W/c users fit poorly. Use of tested products recommend those tested to recognized industry standards. *Safety restraint--one designed and tested for purposes of restraining a vehicle occupant during a crash even, i.e., lap and shoulder belts in all cars. *Postural support--supports used to help maintain a person in the desired seating posture while seated in a W/C.

5 Guidelines for Appropriate Fit = Incorrect = Correct (1) Shoulder belt shoulder should pass over mid-point of the shoulder and leave the rear of the occupant in an upward direction. A downward direction could place large compressive loads on the spine in a crash event.

6 Wheelchair Securement dinosaurs are still out there!! still many untested devices being used side-facing arrangements still in use, such as wheel clamps belt-type vs. docking docking devices can provide more independence belt-type are simple and less expensive both types can pass industry standards. securement locations location of tiedown attachment on W/C will effect system performance* *Generally, locating the attachment point of four point belt tiedown at a location close to the center of gravity of the combined W/C and occupant gives the best crash result. A good rule of thumb is about above the floor. However, availability of suitable attachment structures often overrides this desired location.

Wheelchair Securement Upper left - experimental

mainly by wheelchair-seated drivers Upper right

Lower right - side facing wheel clamp with

One can only hope that a high impact frontal

7 Wheelchair Securement Upper left - experimental docking device Lower left - docking device used mainly by wheelchair-seated drivers Upper right - classical side-facing wheel clamp securement Lower right - side facing wheel clamp with ineffective occupant restraint. One can only hope that a high impact frontal collision does not occur, as the results would likely be catastrophic.

Four-point Belt-type Wheelchair Tiedown The Industry standard for wheelchair securement in North America The four white pockets are normally secured to the vehicle floor.

8 Four-point Belt-type Wheelchair Tiedown The Industry standard for wheelchair securement in North America The four white pockets are normally secured to the vehicle floor. In this product the rear straps have a ratchet-type tightening device that allows all four straps to be tightly secured. Most belt-type tiedowns used today have been tested to the industry standard (SAE-J2249).

9 Finding Locations for 4-Point Belt-type W/C Securement Main Problems: Most W/Cs do not have designated attachment locations, Some structures are not strong enough i.e., armrests, footrests, wheels In many vehicles wall-side attachment location is hard to reach, Many users and operators would rather not bother.

10 Occupant Restraints Main Problems: Poor occupant fit. Hard to fit snugly to occupant. Requires an attendant to apply or attach Invades occupant s private space. Not seen as important by many users and operators and are therefore ignored.

11 Summary of Key Principles Forward facing in vehicle. Securement to structural parts. Seat frame only or W/C frame only. Clear path to vehicle anchorages. No inadvertent release of tiedown. Location in vehicle not close to hard objects.* Stable under normal driving conditions.* *Industry standards stipulate how close a wheelchair should be located to other objects in the vehicle, so that during a crash event the occupant s body will be less likely to strike an injurious hard object. Although the focus of safety standards is on crash safety, it is also most important to users that they feel stable and secure during routine driving, i.e. vehicle turning, braking and accelerating.

Manual W/C Standard X Frame Red arrows illustrate good tiedown strap attachment locations* Red wire wraps* can be added to frame to provide permanent markings of securement locations Graphic

12 Manual W/C Standard X Frame Red arrows illustrate good tiedown strap attachment locations* Red wire wraps* can be added to frame to provide permanent markings of securement locations Graphic compliments of Washtenaw School District, Ann Arbor, MI * The indicated locations for tiedown attachment to structural members would take precedence over the ideal vertical center of gravity location. However is this case, a manual W/C, both vertical locations are about the same. This is not the case for most heavy powered W/Cs * Brightly colored and easy to apply wire wraps can be obtained from most electronic stores,i.e. Radio Shack

13 Manual Wheelchairs Wheels and footrests are a no, no!* Graphic compliments of Washtenaw School District, Ann Arbor, MI * Most wheels and detachable components, such as footrests and armrests, will not withstand the forces associated with even a minor crash event.

14 Manual Wheelchairs Single belt attachment to collapsing X structure is not good! Graphic compliments of Washtenaw School District, Ann Arbor, MI

15 Manual Wheelchair Structural frame members?* Yes, attach here! For most manual W/Cs and many older powered W/Cs the red marked securement locations can be found as follows: Rear: at the welding junction of backrest and seat frame, about 1-3 below the seat. Front: at the welded junction of the tubular structure to which the front casters are attached. Or at the same level as rear tiedown, but on the front portion of the seat structure.

16 Manual Wheelchairs Contemporary Wheelchairs? Attachment on a frame location is best!* Graphic compliments of Washtenaw School District, Ann Arbor, MI Even on many contemporary W/Cs the best structural locations for tiedown attachment is the same as previously indicated

Powered Wheelchairs traditional frame style structural members are usually accessible in shown locations Graphic compliments of Washtenaw

17 Powered Wheelchairs traditional frame style structural members are usually accessible in shown locations Graphic compliments of Washtenaw School District, Ann Arbor, MI For heavy, powered W/Cs it is much more critical that the strongest structural locations be located front and back

18 Powered Wheelchairs Traditional frame style common rear location (under seat)

Powered Bases: a side view 2 2 1 1 Secure to base and not seat, if possible.

19 Powered Bases: a side view Secure to base and not seat, if possible.* 1)=first choice, 2)=second (on seat frame) Graphic compliments of Washtenaw School District, Ann Arbor, MI *Since the strength of attachment between the seat and base is often questionable, tiedown securement to the W/C base is probably the most prudent choice, whenever possible.

20 1 2 Powered Bases: a rear view seat inserts may need to be modified to allow hook access to frame structure Graphic compliments of Washtenaw School District, Ann Arbor, MI

Stroller Bases Secure to stroller base, not seat frame Some bases have attachments points that have been crash tested* Some have integrated occupant restraints Graphic compliments of Washtenaw School

21 Stroller Bases Secure to stroller base, not seat frame Some bases have attachments points that have been crash tested* Some have integrated occupant restraints Graphic compliments of Washtenaw School District, Ann Arbor, MI Industry performance standards are now being used to test the crash performance of wheelchairs, including stroller bases. Surprisingly, stroller bases often do better than W/Cs, so one can not easily ascertain the crash worthiness by merely looking at the device. Information on the industry test standards is posted as a separate lecture in the Wheelchair University lecture series.

22 Stroller Bases Note built-in front attachment point Rear bar structure is a good location for rear attachment Graphic compliments of Washtenaw School District, Ann Arbor, MI

recommended tilt angle during transport = 15-20 1) If there is a concern about the

23 Tilt-in-Space most tilt mechanisms are not designed for crash forces (1) seat structures back (L) and front (R) preferable in this case max. recommended tilt angle during transport = ) If there is a concern about the strength of the tilt mechanism an auxiliary strap can be used in the rear, which links the seat and base frames at the set tilt angle.

24 Tilt-in-Space Bases In some cases, the lower seat structure is the only available location for front and rear securement. ( see next slide) Graphic compliments of Washtenaw School District, Ann Arbor, MI

Rear: a location on the rear seat structure--seat tilted

25 Tilt-in-Space Bases front seat structure rear Front: a location on the lower seat frame, below the footrests. Rear: a location on the rear seat structure--seat tilted in space about 30, so it appears between wheels on side view.

26 Specialty Inserts and Harnesses What is wrong with this arrangement? Graphic compliments of Washtenaw School District, Ann Arbor, MI Sometimes crash-tested harnesses are used when other alternatives do not exist. In this case, it is used without appropriate W/C securement, which would create be a very poor safety situation.

27 Docking Securement Dictated by hardware design. Mainly used in private vehicles for drivers. Single point attachment will not pass 30 mph, 20g test. The use of tested products is critical.

28 Inserts and Accessories* Head supports Trunk and pelvic postural supports Seating inserts Insert attachment hardware Trays Respirators All should be suspect from the crash safety viewpoint! Industry performance tests related to cash-worthiness do not exist at present, but are under development.

29 Inserts and Accessories How much Strength? attachment hardware, postural supports, head rests, lateral supports, trays, controls. Graphic compliments of Washtenaw School District, Ann Arbor, MI One big question is how strong do these accessory components need to be? In some cases it may be better to have a weaker component thereby creating less chance of creating an injury. A difficult standards-setting problem.

30 Air Bag Injury Prevention Concepts Cause: Rapid deployment of partially inflated bag against head, neck or chest of closely seated driver/passenger At increased risk: Young children Infants in rear facing safety seats Small adults W/C seated driver required to sit close to steering column Pregnant women

31 Air Bags Safety Tips Intended to provide supplemental protection only! Occupant restraints should fit snugly. Position no closer than to steering wheel. Pedal extenders can allow more space for small persons. Adjustable tilt steering wheel or W/C seat height may help. Can request disconnect waiver from NHTSA. Unfortunately, local mechanics often reluctant.

32 Air Bag Safety Tips - cont d. When possible avoid hand position directly over steering wheel airbag compartment. Frail passengers and children less than 4 11" (or Age 12) should ride in rear seat. Never place a child safety seat in the front seat. When purchasing a new vehicle evaluate for maximum airbag distance.

33 Air Bags and Vehicle Modifications OEM sensors used to deploy air bags are optimally placed on vehicle. Control modules are often placed beneath the driver's seat. Changing van structure could void optimization of sensor/controller location. May result in faulty deployment during less severe crashes. Auto manufacturer's working to evaluate affects of vehicle modifications. Future "Smart" air bags may help W/C-seated drivers.

34 Air Bags---the Future?? SMART Air Bags... Weight Sensor Grid integrated into seat. will not activate bag unless minimum weight is registered. Sophisticated Crash Sensor Delineates between minor and severe crashes and inflates bag accordingly. Ultrasound and Optical Sensors Mounted throughout vehicle to detect passenger size and adjusts air bag deployment rate.

35 Other Issues... Low back chairs-no good solution Lateral instability-new industry standard will disclose rating between W/Cs. Rear impact -lack of suitable head supports. Side impact - limited protection. Roll over - W/C occupant is usually seated higher then other passengers??

36 Requirements /Provisions in New Voluntary Industry Standards General Requirements testing to specific design/performance criteria key information disclosed in presale literature user information must be made available Informative Design Guidelines for: seat inserts postural supports other accessories

37 Key Design/Performance Requirements Transit W/C Standards (ISO) "the W/C shall not prevent an independent pelvic belt from lying across the pelvis----" "if an integrated pelvic restraint is anchored to the W/C, the design provides a pelvic belt angle between to the horizontal..." W/C must have four labeled securement attachment points

38 Labeling/Information Disclosure Requirements Transit Wheelchair Standards "locations of securement points clearly marked with a symbol readable at a distance of 1 m." "any postural supports provided with W/C shall be labeled as unsuitable for safety restraint unless they comply with WTORS standards select test results disclosed in pre-sale literature

39 Summary Orientation of W/C within vehicle is important. Fit of restraints is important. Securement attachments on structural members. Avoid air bag hazards. Key provisions of voluntary industry standards Strongly recommend use of tested products.

40 More Information... Wheelchair Tiedown and Occupant Restraint System- Application Guidelines: ml#anchor Current Status on standards development: Research Publications:

WHEELCHAIR TRANSPORTATION STANDARDS W/c Tiedown and Occupant Restraint Systems-WTORS

WHEELCHAIR TRANSPORTATION STANDARDS W/c Tiedown and Occupant Restraint Systems-WTORS Douglas Hobson, Ph.D. RERC on Wheeled Mobility Department of Rehabilitation Science and Technology University of Pittsburgh