Requirement #1
Requirement:
The device must be able to monitor the skin temperature of the hand, specifically the fingers and thumb.
Specification:
No skin temperature greater than 43°C.
No skin temperature less than 15°C.
Justification:
The temperature of the skin must remain within the therapeutic range in order to provide a safe and effective therapy for the patient. Monitoring skin temperature will ensure that the device will not cause damage to the patient’s skin or tissue, as the change in intramuscular and intra-articular temperature will not exceed that of skin temperature. The fingers are the part of the hand most susceptible to temperature change than the rest of the hand.
Requirement #2
Requirement:
The device must not harm the user while the device is in use.
Specification:
Device should automatically shut off if the skin temperature exceeds 43°C or drops below 15°C. The device should have a manual switch off in accordance with: ISO/TS 19218.
Justification:
The device should remain within its programmed parameters in order to safely deliver the intended therapy to the user.
Requirement #3
Requirement:
The device must be capable of being used by the user outside of a clinical setting with no training.
Specification:
A score of greater than 68 on the System Usability Scale will classify the device as above average in terms of usability.
Justification:
A simple and intuitive design will allow users to conduct the therapy outside of a clinical setting and without the need for a healthcare professional. This will grant the user therapeutic autonomy in personal locations.
Requirement #4
Requirement:
The device must be able to transfer heat into and away from the hand in controlled cycles.
Specification:
Heat will be applied to the patient’s hand until temperatures between 35.0°C and 40°C are detected by the device. These conditions will be maintained for 20 minutes, after which heat will then be removed from the patient’s hand until temperatures between 15°C and 18°C are reached. Upon reaching the cooling temperature range, the device will maintain the temperature for another 20 minutes.
Justification:
Controlled heating has been shown to increase range of motion while controlled cooling has been shown to decrease the intensity of pain. The application of cyclic heating and cooling for a set interval of time has been shown to achieve these therapeutic effects.
Requirement #5
Requirement:
The device must be light enough to transport and use with one hand.
Specification:
Based on the average weight of a female (62 kg), the device must weigh equal to or less than 6.2 kg (or 13.7 lbs).
Justification:
The average person can lift up to 10% of their weight in one hand without affecting their gait cycle. In the interest of making the device available in personal locations, it should be portable and easy for the user to carry with one hand.
Requirement #6
Requirement:
The device must fit on the majority of adult human male and female hands.
Specification:
Using the 5th percentile of women to the 95th percentile of men, the device must fit:
Hand Breadth (57): 7.34-9.76cm
Hand Circumference (58): 17.25-23.03cm
Hand Length (59): 16.50-21.06cm
Wrist-Thumbtip Length (130): 10.70-13.59cm
Justification:
Female’s hands are on average smaller than male’s hands, while arthritis affects women more than men [6, 7]. A properly fitting device would be more effective at applying and removing heat from the patient’s hand.
Requirement #7
Requirement:
The device must be able to be powered by commercially available rechargeable batteries.
Specification:
A rechargeable battery with a voltage of 9-12 V and a current draw of 1500-2000 mAH will be used.
Justification:
Having a rechargeable battery benefits the consumer by enabling them to use the device multiple times before needing to recharge it.
Requirement #8
Requirement:
The electronics used for the device’s function must be shielded from the heating and cooling elements in the device, such that the electronic components are not at risk to be damaged by the hot or cold temperatures.
Specification:
The environmental range for the equipment under continuous operation is 5-40°C, as specified by ANSI/AAMI HA60601-1-11:2015
Justification:
ANSI/AAMI HA60601-1-11:2015 is the standard that applies to the safety and performance of medical electrical equipment intended for home use. Keeping the electrical equipment within the temperature ranges specified in this standard, or protected from temperatures that exceed it, is imperative for protecting the integrity and safety of the electrical components.
Requirement #9
Requirement:
The electronics of the device must be resistant to internal and external sources of moisture as well as from external contamination such as dust or other small debris.
Specification:
The device must be rated at least IP43 and pass IP standards as outlined in ANSI-IEC 60529.
Justification:
The electronics must be protected from sweat or other sources of moisture or external particle exposure. This prevents interruption or damage to the functionality of the device.