Product Design Specification



Product Design Specification

Support Device for iSCAN

Team Members:

Anna Dirienzo

Katelyn Lesk

Amber Loree

Jude Menie

Project Advisors:

Daniel McChesney, MD

Nobuhiko “Poohsan” Tamura, Ph.D.

Functions (Support System):

This project focuses on designing an efficient support of an ophthalmodynamometry device that will be used to measure intracranial pressure (ICP) in a non-invasive manner. The support device intends to mechanically stabilize and control the iSCAN to facilitate ease of use and provide more precision for a physician, or emergency room staff to measure a patient's ICP. In addition, the device must be sensitive enough to measure small pressure changes; thus, the support system will contain a counterbalancing mechanism to ensure that the weight being applied to the eye is accurately controlled. The support device will also be portable and easy to store.

Functions (iSCAN):

The iSCAN system is the first noninvasive ICP monitor that facilitates the rapid and reliable diagnosis of neurological disease by utilizing the close anatomic relationship between the eye and the brain. The iSCAN applies pressure to the exterior of the eye while imaging the central retinal vein, and relates the measurements of various intraocular pressures induced to observed changes in the central retinal vein. The iSCAN can also be used for simple measurements of intraocular pressure and for imaging the retina.

Client Requirements (Support System):

• Effectively support a 1770g ophthalmodynamometry device, the iSCAN

• Align with the iSCAN and distribute the center of gravity evenly

• Must be able to be stabilized in any 3D position as the device will be used in an emergency medicine setting

• Ability for the user to control the force applied to the eye in a precise and controlled manner that can be easily measured

• Must be sensitive enough to measure small pressure changes

• Be compact so it can be mobile, and easily stored in a hospital setting

• Must be able to be sterilized using ethanol

Client Requirements (iSCAN):

• To accurately and reproducibly measure ICP in an emergency room setting

• To be easily operated by physicians and/or ER techs

• To take measurement without causing any discomfort or harm to the patient

• To integrate the application of pressure to the eye, the observation of the retinal vein, and the inference of ICP into a single handheld unit

• To allow for the full ICP measurement procedure to take place in less than five minutes

Design Requirements:

a) Performance Requirements (Support System): The device should be able to support the 1770 g opthalmodynamometry iSCAN device. It should make the process of measuring ICP available to everyone in a hospital setting instead of only highly-specialized physicians, which will allow the staff to make these measurements as frequently and quickly as needed. The device must also be easily converted to standard measurements to make readings easier and faster. In addition, the support device should be portable and easily stored, as well as contain the components to make large and fine adjustments for accurate placement of the device. Also, all parts need to be easily operated, including stabilizing attachments that are going to be made by physicians in an emergency setting.

Performance Requirements (iSCAN): The device should be able to provide an accurate and precise measurement of ICP in an emergency room setting. The interface and data production should be easily used and understood by the physician. The iSCAN should calibrate itself by measuring the ambient air pressure and storing it as a baseline. The iSCAN should continuously display the central retinal vein and the intraocular pressure as pressure is slowly applied. The iSCAN should eventually be capable of locking on to the central retinal vein, recognizing the collapse of this vein, registering the intraocular pressure at the point of collapse, and converting this sampled pressure to ICP at the press of the button.

b) Safety (Support System): The device must not harm the patient in any way. The device will not have any abrasive material or sharp areas that can harm a patient. It must be carefully operated. The support device must equally distribute the weight of the iSCAN so that it does not fall upon a patient. Locked wheels should be considered. Also, precautions should be taken to appropriately shield all electrical components, and cause of shock, from the patient. Lastly, a safety strap should be considered to minimize risk of the device falling onto the patient.

Safety (iSCAN): The device should take the measurement without applying more pressure than is needed to obtain the measurement, as to not cause damage to the vein. Intraocular pressure must be continuously monitored to mitigate the risk of excessive applied pressure and an alert system should also be included as a warning if excessive pressure is applied. Sterilization issues should be addressed by developing a disposable lens. The iSCAN must also comply with the following regulations:

• Must not have any flammable materials near the light source

• Must comply with section 5.5 “Optical radiation hazard with ophthalmoscopes” (along with section 6.2 and Annex C) of the ISO (International Standards Organization) 10942 and/or 10943

• Optical radiation emissions from the device must not exceed the Threshold Limit Values (TLV) for optical radiation established by the American Conference of Governmental Industrial Hygienists (ACGIH) based on a worse case clinical exposure situation

• Must be compliant with optical radiation hazard guidelines defined by ISO 15004 (including spectral irradiance profiles) for:

o Visible wavelength range 400 nm to 700 nm

o Ultraviolet (UV) wavelength range 250 nm to 400 nm

o Infrared (IR) wavelengths greater than 700 nm

• Must comply with electrical safety standards set by the FDA (IEC 60601-1)

• Must follow regulations set forth for contact lenses, tonometers, or any instrument which comes in direct contact with the eye

c) Accuracy and Reliability (Support System): The device must be able to support the 1770 g device. It must be sensitive enough to measure small pressure changes. The device also must be able to accurately measure and adjust for the force being applied, which is in the range of 0-3.9 N with increments as small as 0.05 N. Large forces should be converted to grams to make it easier for the physicians to adjust the weight based on standards they are familiar with. The device must be able to hold the position it is set in without relaxation of the system, which could possibly alter ICP readings.

Accuracy and Reliability (iSCAN): The iSCAN should provide consistent and reproducible readings. The device should be accurate enough to sense the small pressure changes of the measurement (the intraocular pressure will be between 20-140 mmHg).

d) Life in Service (Support System & iSCAN): The support system must be able to withstand multiple uses in one day within the hospital. Once the actual materials of the support system are determined and tested, and approximate expectancy will be concluded.

e) Shelf Life (Support Device): The support device should last 5-10 years with proper handling and maintenance.

Shelf Life (iSCAN): The device should have a comparable shelf life to the support system with proper maintenance and part replacements.

f) Operating Environment (Support System & iSCAN): The device should be able to withstand normal temperatures (in the range of 20-25 ºC), pressures, and humidity. It will be subjected to multiple patients per day. The device might also be subjected to fluids and/or dust from everyday use. The noise of the device must be relatively low so as to not interfere or irritate the physicians or patients. In addition, the device should create no vibration, as this can cause injury to the patient. The apparatus also should not interfere with any other instruments or monitoring systems electronically.

g) Ergonomics (Support System): Ideally, the device should be about 5 feet tall or at least as tall as a hospital bed. It should be able to reach any size patient on the hospital bed. The force must be able to be adjusted to 0-3.9 N in increments as small as 0.05 N with an easy-to-operate interface. Also, it should preferably be coated in a non-slip gripping material. And, it should be easily lifted by and maneuvered by ER staff, no matter their physical ability.

Ergonomics (iSCAN): The iSCAN should have an easy-to-use interface, making it easy to read and operate. It should be easily detached and reattached, as far as weight and support connections are considered, for sterilization purposes. Eventually the iSCAN should be able to interface with a generic hospital montitor.

h) Size (Support System): The support system needs to be above the height of a hospital bed (about 5 feet tall) and long enough to reach any patient on the hospital bed. It also must be compact enough for easy storage, and as to not obstruct the physician’s view of the patient.

Size (iSCAN): There are no known size limitations, however, it must attach to the support device and be easily maneuvered by the operator.

i) Weight (Support System): The support device must weigh enough in order to support a 1770 g device but also be easily handled and stabilized; with the majority of the weight distributed in the base.

Weight (iSCAN): The weight should be as small as possible as to not exceed the limitations of the support device or cause unnecessary danger to the patient.

j) Materials (Support System): Steel will be used because it is easy to clean and sterilize. The material needs to allow for both flexibility and stabilization. The material for the large adjustment will include a metallic gooseneck.

Materials (iSCAN): There are no restrictions on materials, however the material being used should be able to be sterilized by alcohol or ethanol. Material considerations will need to be made for all separate parts of the iSCAN including a lens, a visualization screen, and a control pad.

k) Aesthetics, Appearance, and Finish (Support System & iSCAN): The appearance is not of great concern, although it should at least look safe and easy to operate.

Product Characteristics:

a) Quantity (Support System & iSCAN): One operational prototype.

b) Target Product Cost (Support System): Expected to cost around $1000 and $500 will go towards any extra equipment needed.

Target Product Cost (iSCAN): Final production cost is not known. However, the final cost should be competitive in the market of sale.

Miscellaneous (Support System & iSCAN)

a) Standards and Specifications: FDA approval is required before human subject trials. And, animal trials will begin in June of 2007.

b) Customer: The customer would be a certified staff member at the hospital who would prefer the device to be easily stored and easy to use.

c) Patient-related concerns: The device will need to be sterilized after use.

d) Competition: No other non-invasive devices are known to achieve this objective.

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