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Human Factors Analysis

Nichole McPherson

Counter-Irritation Device

6.1 Device Overall

The extracorporeal counter-irritation (ECI) device minimizes anxiety and pain associated with needle pricks by externally administering counter-irritation to children in the form of music, flashing lights and vibration. The ECI device has the potential to comfort everyone receiving an injection, vaccination, IV or catheter regardless of age, however the first generation of ECI devices will be designed for children aged 5 to 8. Considerations for the user were incorporated into the device design not only in its effectiveness but also in its’ comfort. The ECI device is not bulky, heavy or uncomfortable. The ECI device occupies less than six cubic inches and is shaped like a turtle. The total weight of the ECI device is less than 1 pound. The device attaches via a soft, easily adjustable arm band.

Important components of the ECI device include the turtle shaped case, the Velcro arm band, and the electrical components. A nine volt battery powers a motor, sound chip, speaker and LEDs.

6.2 Device User Interface

The first component that comes into contact with a user is the arm band which is used to attach the device to a limb (usually the arm). The arm band is made of grade 1 neoprene (hook & loop) and is easily fastened. The second component which contacts users is the case which periodically needs to be opened in order to change the battery. Though the case is waterproof and made of injection molded plastic, proper closure of the case is important to ensuring the safety of all users. The third component is the battery. Batteries always come labeled with their positive and negative ports however the docking site in the device for the battery will also be labeled positive and negative in the form of commonly used symbols ‘+’ and ‘-‘ respectively. Lastly, users interface with the power button which is a round push button that has a diameter of 2cm. Pushing the button once will turn the device on (all three stimuli will be powered). Then pushing the power button a second time turns the device off (all stimuli will be off). The power button will be marked by the universal symbol for power which will be etched into the case surface centered on the button. Operating instructions will be provided with the device along with a schematics detailing the procedure for operating the device, changing a battery and cleaning the device. No training will be provided to users, however information on areas of the body most receptive to counter irritation will be included along with a list of cautionary instructions (i.e. do not submerge in water, do not let unsupervised children play with device).

6.3 Device Use

The user is expected to interact with the device when operating the device, changing the battery and cleaning the device. In order to operate the device, the user must use the arm band to attach the device properly to a patient, press a button to turn the device on, press the same button to turn the device off, loosen the arm band and detach the device. Changing a battery requires the user to open the case, switch batteries and close the case. The device can be cleaned using typical alcohol based solvents used for cleaning in hospitals and doctors offices. The user must wipe the case with cleaning solution and wash the arm bands in a machine washer. During any of these tasks, it is anticipated that the user could contact all regions of the arm band and case. Also during a battery change or cleaning it is feasible that the user will contact a small section of the inside of the case. Though most electrical components will be isolated from the user, at least the docking ports for the battery will be exposed to the user. During pressing of the push button the users’ fingers will not be at risk of shock. While caution and care are advocated for when operating, maintaining and cleaning the device, it is inevitable that rough handling of the device will occur. The device was designed to withstand rough handling.

6.4 Device User Population

The intended population of device users is nurses who administer injections, IVs and catheters, however parents or patients themselves may also assist in the attachment of the device. The only population for which the device is not intended to be used by is young children (under the age of 12). All other populations might not have motivations to operate the ECI device, however the device is so user friendly and safe that all other populations should be able to operate, maintain and clean the device without fear of injury.

The anthropometry of nurses fingers were considered when choosing a push button size and its location on the device. Also the mechanism for opening the case, which involves pinching a small mechanical lever was made big enough to accommodate 95% of females and 50% of males. Since the device could potentially be marketed worldwide, universally accepted symbols were used for labels on the device instead of words so that language is not a barrier to device use. No training will be provided to users, however information on areas of the body most receptive to counter irritation will be included along with a list of cautionary instructions (i.e. do not submerge in water, do not let unsupervised children play with device). Also basic instructions for operation including schematics and details for changing the battery and cleaning will be included in the packaging of the device in the form of small handouts.

6.5 Device Use Environments

The device is intended to be used in clinics, labs, ambulances, hospitals and doctors offices however that is only because those are the most common places that patients receive needle pricks. Other environments that were suitable for needle pricks would also be suitable for the ECI device. The ECI device could be used world wide, not just in America. The device should not be used in extremely moist conditions such as outside in the rain or underwater. The device should not be used during serious procedures where counter-irritation could interfere with a procedure or distract doctors or nurses. Also device should not be used in situations were patient is in extreme pain that is not induced by a needle prick. Lastly the device should not be used in environments where other equipment may be compromised by the presence of the ECI device.

6.6 Use-Related Hazards

First hand operation and observation of the device were conducted in practice scenarios (without any needle prick) and clinical scenarios. Both patients and nurses were interviewed independently and as part of focus groups. Frequency of the hazard (or identification of the hazard) and level of hazard were used to prioritize use-related hazards. The main hazard identified thus far in the developmental process is rough handling which could result in at most a minor shock to the user or patient if the electrical components were exposed. Other hazards identified include minor shock via submersion of device in water (in an attempt to clean the device) and shock from handling a battery. Efforts have been made to make the case waterproof to prevent minor shock from submersion and also to make the case durable to prevent the exposure of electrical components.

6.7 Verification and Validation

The device will undergo several tests. First a repeatability test will be performed to determine whether or not the device functions as it should. Activation of each type of stimuli will be required upon pressing the power button. Trials will be performed and the prototype must function correctly 5 times out of 5 trials. Second preliminary studies will be performed using the first prototype which assess which of the three stimuli used for counter-irritation are most effective. In addition to clinical trials for this study, mock situations with group members will be run to identify design flaws and potential human errors. Subsequent tests evaluating whether the product design specifications have been met will be performed. For example the device will be weighed to ensure it weighs less than one pound. Also surveys will be used to evaluate whether the device reduces anxiety and pain associated with needle pricks. With a revised prototype a third study will be performed in clinical settings by users who have had no training and the surveys will again be used to assess whether the ECI device reduced anxiety and pain. Observations will be made during the test and the users will be interviewed after the testing is finished.

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