High capacity implantable data recorders: system design and experience in canines and Denning black bears.
BACKGROUND
Implantable medical devices have increasingly large capacities for storing patient data as a diagnostic aid and to allow patient monitoring. Although these devices can store a significant amount of data, an increased ability for data storage was required for chronic monitoring in recent physiological studies.


METHODS
Novel high capacity implantable data recorders were designed for use in advanced physiological studies of canines and free-ranging black bears. These hermitically sealed titanium encased recorders were chronically implanted and programmed to record intrabody broadband electrical activity to monitor electrocardiograms and electromyograms, and single-axis acceleration to document relative activities.


RESULTS
Changes in cardiac T-wave morphology were characterized in the canines over a 6 month period, providing new physiological data for the design of algorithms and filtering schemes that could be employed to avoid inappropriate implantable defibrillator shocks. Unique characteristics of bear hibernation physiology were successfully identified in the black bears, including: heart rate, respiratory rate, gross body movement, and shiver An unanticipated high rejection rate of these devices occurred in the bears, with five of six being externalized during the overwintering period, including two devices implanted in the peritoneal cavity.


CONCLUSIONS
High capacity implantable data recorders were designed and utilized for the collection of long-term physiological data in both laboratory and extreme field environments. The devices described were programmable to accommodate the diverse research protocols. Additionally, we have described substantial differences in the response of two species to a common device. Variations in the foreign body response of different mammals must be identified and taken into consideration when choosing tissue-contacting materials in the application of biomedical technology to physiologic research.
Laske
Timothy G
TG
Department of Surgery, University of Minnesota, Minneapolis, MN 55432, USA.
Harlow
Henry J
HJ
Werder
Jon C
JC
Marshall
Mark T
MT
Iaizzo
Paul A
PA
D000054:Acceleration; D000818:Animals; D003936:Diagnosis, Computer-Assisted / Q000295:instrumentation* / Q000379:methods; D004285:Dogs; D011211:Electric Power Supplies; D015716:Electrocardiography, Ambulatory / Q000295:instrumentation* / Q000379:methods; D004867:Equipment Design; D019544:Equipment Failure Analysis; D006339:Heart Rate / Q000502:physiology*; D016247:Information Storage and Retrieval / Q000379:methods*; D008904:Miniaturization; D009043:Motor Activity / Q000502:physiology*; D012815:Signal Processing, Computer-Assisted / Q000295:instrumentation*; D001503:Ursidae