Medical Device Link has an interesting story on wireless microsensors written by Campus Micro Technologies, a German sensor system integrator. The application for microsensors discussed includes the creation of partly and fully autonomous therapeutic feedback (closed-loop) control
systems. The idea is that this "new" type of implantable pressure monitoring system can provide long-term monitoring inside the human body (at least 10 years or more).
Requirements for such a system include minimal power that is supplied from
outside the body rather than incorporating a battery, which limits the
lifetime of the implant. Packaging and
assembly of the implant is also critical regarding biocompatibility and
the long-term functioning of the system. The story provides examples of work being done on developing these systems for measuring intracranial pressures, continuous measurement of intraocular pressure, and for use as feedback to ensure the quality of therapy delivery.
The realisation of truly autonomous sensor systems for therapy is
closer than ever. Some of the remaining issues to resolve include the
question of long-term stability over periods of several decades and
further integration of currently available single modules into actual
systems, where those individual modules closely interact. These
require, for example, the use of multisensor networks, improved
algorithms to combine the output of those sensors, extracting relevant
information from pure data, and rule-based decisions controlled by the
Closed-loop control systems are in widespread use in the industry
and are currently a focus of intense research. They are able to make
their own decisions to try to reach and control a preset target.
Examples include automated insulin delivery in response to regular
blood-glucose measurement in diabetics and propofol-infusion coupled to
electroencephalogram-derived parameters of unconsciousness in
The integration of miniaturised, long-term stable pressure sensors
such as those described in this article into devices such as
implantable blood pumps, bladder stimulators and shunt systems is one
of the preconditions for realising closed-loop control systems for
these applications. Stand-alone monitoring devices (sensing devices
allowed to measure pressure without further integration) and
closed-loop systems (systems with integrated sensors and actuators)
will be necessary in the future. They will be required for monitoring
the success of therapy and its optimisation and for adapting therapy to
the individual and actual conditions, rather than relying on past
experience and averaged data from groups of patients.
As an intermediate step towards fully autonomous implants, therapy
can be continuously monitored and parameters changed as necessary by
the clinician via wireless communication with the implant. Therapy will
be remotely monitored with the help of the implant and data will be
sent on demand to the clinician for further evaluation. The clinician
can then change the therapy based on the data provided by the implant.
Those partly autonomous therapy systems will still rely on the
expertise and intervention of the health-care professional. Visits of
patients to hospitals or the doctor will be reduced to a necessary
minimum, while increasing the quality of care that is provided.
Hmm, sounds like the integration of distributed medical devices to produce
"error-resistant" systems with safety interlocks between devices. Where have I heard that before?