Initial Human Factors Analysis



Initial Human Factors Analysis

REVISION 4 (Final): Revised 4/17/2006

BIOE 1160/1161: Bioengineering Design

Calano, Kumar, McNeal, Odle

Overall Device Characteristics

• The modified design will function to support the head of patients suffering from camptocormia, or dropped head syndrome, to allow them to regain adequate visual and physical interaction with their environment. The modified brace will allow a patient to move his neck in the lateral direction. The brace will be girth adjustable. Height adjustability will be provided via a small, medium, and large brace. Custom adjustability will be available by altering the height size of the chin padding.

• This brace will primarily benefit patients suffering from ALS, MS, or other neurodegenerative diseases. These patients do not have proper muscular neck support, and require a neck brace to maintain appropriate positioning for everyday interaction and activity.

• The modified neck brace incorporates what is known as an “open” or “wire frame” design. The brace fits snugly to the contours of the patient’s neck and is thus roughly the same size. Different sizes of neck brace will be manufactured to suit necks of all sizes. The optimal weight of the brace is 8-10 oz. and the color is neutral to optimize blending with skin tone. The vertical struts and chin track support the chin and allow for lateral rotation via a T-groove track system. The wire chest piece distributes the load of the head evenly across the chest, and to allow for even distribution of the force on the sternum, an additional padding piece was incorporated.

• This brace is being designed to compensate for the ineffective designs of current neck braces. Current braces include the Philadelphia collar, the Aspen collar, and the Headmaster. Because current designs are tailored for use on patients with a neck injury, they assume some level of neck strength in their design. In ALS patients, however, muscular degeneration results in a complete lack of neck strength. Thus, current neck braces are unable to provide the proper support for these patients. Furthermore, current neck braces are designed to hold the head in a fixed position to allow the neck to heal. Our modified design will allow neuromuscular degenerative disease patients to maintain a level of lateral mobility which matches the amount of neck muscle strength they still possess.

Device User Interface

• The device will feature a chin rest with open-cell, memory foam padding which, since it is not washable, can be replaced.

• The device will feature a T-groove track and chin piece which allow for 60 degrees of lateral rotation of the neck.

• The device can be applied by either the patient or a health care worker, pending on the progression of the disease.

• In order to apply the brace, the Velcro straps will need to be placed around the user’s neck and when appropriately positioned the straps can be fastened. Appropriate positioning requires that:

o The user’s chin will be fully inside the padded chin cup

o The chest wire frame will be appropriately positioned

o The sternal padding piece will be in at the center position of the chest wire frame piece

o The back padding piece will be placed according to the curvature of the back fo the head and neck

Device Use

• The user should be provided with instructions & guidelines for device use, which would include:

o Instructions for wearing the device

o Proper positioning and adjustability instructions

o Laundering instructions

o List of symptoms resulting from improper use and positioning

Ideally, the patient should consult a clinician for the initial fitting and adjustments to ensure proper device use.

• Set up and maintenance:

o The device will be packaged already assembled, with detailed instructions included in the packaging.

o Girth adjustments are made by adjusting a Velcro strap around the patient’s neck and can be made by the patient himself or a health care provider.

• Further interaction will occur if the user has enough muscle strength to move his or her neck laterally via T-groove track and chin piece system located at chin level on the front of the brace.

• Both the closed and open cell padding on the device is removable and replaceable as necessary.

• The user may wear this device while carrying out various social and daily activities.

Device User Population

• This device is designed for patients with significant neck muscle weakness also known as camptocormia. These patients are often affected with neuromuscular diseases such as amyotrophic lateral sclerosis (ALS). Some of these patients are capable of lateral head rotation, but do not have muscle strength to keep their head held up.

o The clinician can also be considered a device “user” since they will recommend and adjust the device for their patients.

• This device was not designed for the common population of neck brace users, specifically those with some type of trauma injury. Because this brace will allow lateral mobility, it is not sufficient for the immobilization necessary in many trauma patient cases.

Device Use Environments

• This device is designed for use in any environment that the patient lives within. This would primarily include the home, workplace, health care facility, or social venue. Although perhaps not preferable, the device can be worn while bathing or sleeping.

• Because the device is made to allow proper head positioning and support for normal interaction of the patient with the environment, there is virtually no place that is unsuitable for this device’s use.

Human Use-Related Hazards

• The use-related hazards that have occurred with similar, already clinically available devices include:

o Suffocation

o Skin irritation

o Over heating

o Difficulty swallowing

o Neck soreness/pain

One use-related hazard that has been identified during the developmental stages of the project was determined during a consultation meeting at Hanger Prosthetics and Orthotics Inc. Our group had not taken into account the pain caused by pressure on the sternum. This added pain could discourage patients from using the device even if its use was necessary. With this new found knowledge, our group created a sternal padding piece to evenly distribute the force.

• The processes used to identify and prioritize use-related hazards included

o Clinician interviews

o Orthotist interviews

o Patient interviews

• Significant use-related hazards are in the process of being controlled during the design stage by making the following changes to the failed models:

o Suffocation/difficulty breathing – the use of a hard plastic material with wire frame supports that can be easily adjustable to accommodate the patients neck length will ensure that the brace does not collapse on itself and allows for normal functions

o Skin irritation/overheating – the use of a hypoallergenic, washable plastic molded into an open neck brace design will ensure that the brace provides the maximum amount of skin breathability possible

• The aforementioned strategies appropriately address the possible use-related hazards. These solutions to common neck brace failures were advised by clinicians, physicians, and orthotists, all of whom have dealt with individuals suffering from neck muscle weakness and unaccommodating neck braces.

Proposed Verification and Validation

• The function of the neck brace design will be validated by professionals in the field and by patients. Prototypes of the design will be screened by doctors and patients and they will be asked to complete a questionnaire evaluating the brace according to the following criteria: functionality, comfort, adjustability.

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