clinician removes the compliance monitor from the
patient’s shoe and again connects it via a cable to the
USB port of a PC. The clinician then can upload
the patient identification and time information
and log of compliance data and display and store
the data. The patient’s daily compliance data can
be displayed in numerical and graphical form and
printed out if desired. The clinician then disposes of
the compliance monitor in a manner appropriate for
an electronic device with a small lithium coin cell.
4. THE COMPLIANCE RECORD
The basic information in the compliance record is
whether or not the patient is wearing the therapeutic
shoe, logged in 15-min. epochs, and summarized
as the daily number of hours the shoe is worn. In
addition, the record shows in 15-min. epochs the
patient’s level of physical activity, graded as low,
moderate, or vigorous.
5. FEASIBILITY OF AN IN-SHOE
COMPLIANCE MONITOR
The engineering challenge is to identify small, low-
cost components for the in-shoe compliance monitor
that can provide the needed operating power,
pressure sensing, data sampling, processing, and
storage for up to 8 weeks of unattended monitoring,
as well as communication capability for initializing
a recording and uploading the data afterwards, and
to package them suitably for in-shoe use. These
components now are considered one by one.
5.1. POWER SOURCE
A small, built-in power source is needed with
sufficient capacity to operate unattended for 8 weeks.
It would be desirable if monitor power requirements
are so low that a small coin cell, such as for a hearing
aid or watch, suffices.
5.2. SENSOR
A wa y to determine that the therapeutic shoe is
being worn is to sense the pressure exerted by the
patient’s foot on the insole. A variety of plantar
pressure-sensing systems have been developed [1].
Force-sensitive resistors (FSRs) [2], [3] are commonly
used for this purpose, because they are simple, thin,
robust, and relatively inexpensive. The clinician must
position the single sensor as appropriate for each
patient. For a typical foot, we have found that a good
position is on the underside of the insole beneath the
heel.
FIGURE 1. A FORCE-SENSITIVE
RESISTOR, (FROM[2])
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