| Summary: | The measurement of the interface pressure between a biomedical device and part of the
human body is useful to aid in the design or improve the performance and safety of such devices.
Therefore, a need exists for a transducer to measure interface pressure in these applications. The
development and evaluation of an interface pressure transducer was the main goal of this
research. Surgical retraction, surgical tourniquets and mammography were selected as
demonstration applications for the developed transducer. These target applications were selected
because they represented a wide spectrum of device and tissue characteristics and properties, and
were in common use.
A review of the available clinical, commercial and engineering literature identified a wide
range of transducers and transducer technologies used for interface pressure measurement. The
transducers included pneumatic/hydraulic, fibre-optic, strain based, capacitive and micromachined
technologies. No standard method of measuring interface pressure was described and,
in many cases, investigators cautioned against comparing-interface pressure measurements
obtained using different measurement systems. From this review and an examination of the
biomedical applications mentioned, the design criteria and optimal design specifications for an
interface pressure transducer were defined.
To gain a better understanding of the mechanical response of the interface between a
device, transducer, and tissue to an applied loading, a preliminary finite element model was
developed and studied. The model demonstrated the potential for shear stresses to develop
between the transducer and interface materials. Furthermore a calibration system which
simulated interface conditions was developed to evaluate both existing and developed
transducers for use as interface pressure transducers. This evaluation demonstrated the lack of a transducer whose output was independent of the compliance of the interface materials. As well,
an essential characteristic was identified for an effective interface pressure transducer that could
be used in several applications where the interface material compliance was different.
Based on the knowledge gained from the finite element analysis and existing transducer
evaluation results, a novel interface pressure transducer was developed and evaluated both in the
calibration system and via demonstration applications of surgical retraction and tourniquets.
Under laboratory conditions in the calibration system, the transducer met many of the desired
design specifications. The transducer was tested in the lab under both pneumatic and nonpneumatic
tourniquet cuffs. The transducer worked well under the pneumatic cuff but required
] further development for use under the non-pneumatic cuff. The transducer was also integrated
into a surgical retractor and evaluated in five clinical trials. It met many of the desired
specifications for this application.
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