Solution Requirements
To completely address the needs of users in an efficient manner, we assert that the in-home dispenser cannot be a standalone product. In particular, three additional devices that complement the functionality of the in-home device will need to be engineered:
- A disposable prescription container that facilitates medication dispensing and contains machine-readable administration instructions
- an electronic piece of hardware at the prescription filling pharmacy (hereafter referred to as the “pharmacy” device) that encodes administration instruction onto the disposable containers
- a data server to manage the compliance records of patients who electively allow the in-home device to record and transmit such data for later retrieval by a physician, pharmacist, or caregiver.
The requisite design features for each device are defined with respect to several considerations including necessary device functions, safety, durability, aesthetics, and cost.
In-Home Device Requirements
The in-home device consists of medication storage, dispensing, and “cutting” apparatus, as well as an electronic control system to manage the administration of medication. The in-home device should have an audible alarm with which to alert the user of the need to take medication. At administration time, the device should verify that the user has acknowledged activation of the alarm, and that the user has removed medications from the device. In addition, the user-interface should be capable of indicating to the patient additional instructions regarding how individual medications are to be taken.
Mechanical Medication Dispensing Capability
The capability of the in-home device to dispense different medications in a controlled manner is anticipated to be one of the most complicated functions to engineer. A simple mechanical dispenser could be used if the pills were of a known size and shape. Since a typical user will use more one type of pill, the dispenser should accept pills from a range of sizes.
One question worth asking is precisely how many different medications will the in-home device need to dispense. A telephone survey found “[that about 20% of older men and women had more than 5 prescription medications],” and therefore we believe that an ability of the in-home device to dispense 6 different medications should be adequate for most users’ needs4 .
Since the in-home device is responsible for providing specific quantities of medication at different administration times, it is imperative that it must be able to reliably dispense a defined number of pills from whatever storage containers are present on the device. That is, if one pill is required at a particular administration time, one and only one pill must be dispensed. Unreliability and inconsistency in this area would essentially negate the entire utility of the device, since all one would be doing is replacing the inconsistency of the user’s memory with a mechanical device’s inconsistency.
Limiting the accumulation of “pill debris” resulting from friction between parts that contact pills is also an issue, because such debris can result in device jamming or undesirable accumulation of contaminates such as the debris of previously dispensed medications.
| # | Dispensing Requirements |
|---|---|
| 1 | Correctly Dispenses Pills of a variety of sizes and shapes |
| 2 | Has space to retain multiple (6) different types of medications |
| 3 | Dispense one and only one pill at a time. |
| 4 | Limit to accumulation of pill debris |
Pill Cutting Capability
In accordance with the RERC-AMI project requirements, the in-home device must be able to “cut” pills into multiple pieces if needed for dosing purposes. It is expected that this component will substantially contribute to the complexity and cost of the in-home device. The motivation for the inclusion of this device requirement is the economic cost saving benefits of a user buying pills in bulk doses. As in the case of defined pill dispensing, the primary difficulty in engineering this functionality is the variations in the physical properties of pills. Keeping different medications from contaminating each other is likely to be especially difficult in any “chamber” dedicated to cutting pills, as it easy to imagine a high-energy collision between a pill and cutting element producing small, undesired pill fragments. Either measures to prevent this cross-contamination must be incorporated into the device, or a detailed risk analysis will be needed that demonstrates that the cross-contamination between pills does not pose a substantial health risk.
For simplicity, and because we feel such functionality will be adequate for users’ needs, we only require that our design be able to cut pills in half. Breaking pills into 3, 4, or more pieces will be beyond our device’s capability. As such, we can define the additional requirement that after cutting a pill, the device must be capable of separating the two halves, dispensing one and storing the other in its own compartment for later dispensing.
| # | Cutting Requirements |
|---|---|
| 1 | Fraction Pills into halves |
| 2 | Store Undispensed Half |
| 3 | Limit undesirable pill fragments |
Medication Administration Procedure
There are multiple requirements for an in-home device to fulfill with regard to documenting individual medication dosage dispensing events. At dispensing time the device should produce visual and audible alarms to notify the user of the need to take medication. Since these alarms will activate many times over the life of the device, significant attention must be paid to ensuring that the alarms do not become irritating. For instance, the visual alarm, expected to be a small light, should be easily visible, but probably should not flash on and off. The audible alarm should probably be customizable to an extent.
The dispensing of any medication should always require physical interaction between the user and the device. This is because dispensing medications without user acknowledgment could easily result in the accumulation of multiple doses in the device’s dispensing tray, potentially resulting in a dangerous overdose if the patient consumes many accumulated doses at once. To mitigate this possibility, the device should require that an easily visible button be pressed to turn off the alarms and dispense medications, and a simple weighing element incorporated into to the dispensing tray to detect when pills are removed by the user. If the button is not pressed or a previous dose has not been retrieved, the in-home device should not release medication.
| # | Dosage Administration Requirements |
|---|---|
| 1 | Emit Visual and auditory alarm at medication dispense time |
| 2 | User confirmation of dispense |
| 3 | Do not allow medications to accumulate in dispensing tray |
Electronics
The in-home device will require onboard electronics and appropriate control software for the implementation of much of its functionality. Naturally, the device will require an onboard electronic clock, memory, and simple processor/controller for running the dose scheduling software and detecting the occurrence of dispensing times. Additionally, since we expect the disposable medication containers to carry administration instructions and other data, there must be a compatible data reader or interface with or through which the in-home device can procure administration instructions. Hardware interfaces to user displays, alarms, and mechanical actuators must also be present, along with suitable control software for each of these components. The optional compliance data reporting facility will could be implemented using a telephone line link, requiring a modem and appropriate control software.
| # | Electronics Requirements |
|---|---|
| 1 | Electronic clock, memory and processor |
| 2 | RFID or similar type data reader (serialized barcodes) |
| 3 | Medication warning indicators |
User-Configurable Functions
Since it is expected that most users will be fairly computer averse, the device should not require a significant amount of configuration/programming on their part. Pressing the alarm acknowledgement/dispensing button should be the primary way that the user interacts with the device. However, since the precise timing of the dispensing alarms will affect the user’s daily routine, we believe that the user should have some control over this timing. Of course, it would defeat the purpose of the device to allow the user arbitrary control over when medications are dispensed, since the device is supposed to carry-out prescribing physicians’ instructions. As a compromise between the extremes of total user and total physician control, the pharmacist responsible for entering programming instructions onto the containers of individual medications should only be able to indicate that a particular dose be dispensed at one of five general times of day (i.e. Morning, Noon, Afternoon, Evening, Before Bed). Each of these times should be associated with a particular time interval of the day, and the user should be able to specify the precise time within each interval at which medications will be dispensed. For instance, the user might be able to specify any time between 5 and 9am as the time at which medications they are supposed to take in the morning are dispensed.
Size, Shape, and Weight
Aesthetics are a factor in the design of any medical device for the home, and constrains our design in terms of size and shape. The device should fit on a counter-top, and we feel that minimizing the device’s height and width are more important for avoiding an appearance of bulkiness than the extent of the device over the depth of a countertop. Accordingly, we have set upper limits on the height, width, and depth of our device design’s dimensions of 40cm, 40cm, and 50cm, respectively. Minimizing device weight is primarily a safety issue, because of the possibility of injury to the user by the device’s falling off of a counter. Optimally we would like to keep total device weight below 6kg.
| # | Physical Requirements |
|---|---|
| 1 | Fit onto countertop |
| 2 | weight less than 6kg |
Safety Features
There are a small number of additional requirements on the functionality of the device imposed for the purposes of safety. One is that the dispensing and pill cutting machinery should contain mechanisms to sense when there is abnormal mechanical resistance to motion, and cease operation if such resistance is detected. This is because these components are likely to have moving parts capable of crushing or cutting interfering fingers.
It should not be possible to open the device in the first place with standard tools available in a home, and labeling should be present to warn against self-servicing. Electronic diagnostics should also be run periodically to verify that the dose scheduling code and administration data for individual medications have not been corrupted. Another small feature which should be present in the design is an onboard emergency battery that can provide a small amount of power if the wall socket power fails. This power would be used to indicate through the user-interface that the device is not functioning properly, and cannot be relied on to administer medications.
An important safety feature that warrants special mention is the capability of the device to display warnings and instructions regarding how medications are to be taken (in particular, those that appear on standard prescription bottles). These should be stored along with prescription administration data on the medication containers in machine-readable form. Because we do not want there to be warnings that the in-home device is incapable of displaying, a “general” display will probably be needed, with sufficient size and resolution to be readable by elderly users.
References
4 Kaufman, David W. et. al. “Recent Patterns of Medication Use in the Ambulatory Adult Population of the United States: The Slone Survey”. JAMA. Vol. 287. No. 3. p. 337-344: 16 January 2002.