Long term assessment of blood pressure transducer drift in rhesus monkeys chronically instrumented with telemetry implants.

INTRODUCTION: The accurate assessment of blood pressure is often a key component of preclinical cardiovascular disease/efficacy models and of screening models used to determine the effects of test agents on cardiovascular physiology. Of the many methods utilized in large animals, telemetry is becoming more widely used throughout preclinical testing, and non-human primates are playing an ever increasing role as a large animal model to evaluate the cardiovascular effect of novel test agents. Therefore, we sought to characterize pressure transducer drift of a telemetry implant in primates over an extended duration.
METHODS: We instrumented ten rhesus monkeys with a Konigsberg T27F implant and a chronic indwelling arterial catheter and cross calibrated the diastolic pressure recorded by the implant to the diastolic pressure that was simultaneously recorded through the arterial catheter using a calibrated external transducer/amplifier system.
RESULTS: While all implanted pressure transducers experienced drift to some degree, magnitude of drift varied across animals (range of average drift 0.7-20.5 mmHg/month). Specifically, we found that all implants could be calibrated within the voltage range of the instrument up to 6 months after implantation despite the drift observed. Between 6 and 12 months, 3 of the 10 implants studied drifted outside the defined voltage range and were unusable, two more drifted off scale within 2 years, while the remainder remained within the operating voltage range. DISCUSSION: Given that pressure transducer drift was not consistent across implants or time, these data suggest careful assessment and quantitative correction for in vivo drift of telemetry blood pressure transducers implanted for extended duration should be considered.