Biomechanics of the Sensor-Tissue Interface—Effects of Motion, Pressure, and Design on Sensor Performance and Foreign Body Response—Part II: Examples and Application

Abstract

This article is the second part of a two-part review in which we explore the biomechanics of the sensor-tissue interface as an important aspect of continuous glucose sensor biocompatibility. Part I, featured in this issue of Journal of Diabetes Science and Technology, describes a theoretical framework of how biomechanical factors such as motion and pressure (typically micromotion and micropressure) affect tissue physiology around a sensor and in turn, impact sensor performance. Here in Part II, a literature review is presented that summarizes examples of motion or pressure affecting sensor performance. Data are presented that show how both acute and chronic forces can impact continuous glucose monitor signals. Also presented are potential strategies for countering the ill effects of motion and pressure on glucose sensors. Improved engineering and optimized chemical biocompatibility have advanced sensor design and function, but we believe that mechanical biocompatibility, a rarely considered factor, must also be optimized in order to achieve an accurate, long-term, implantable sensor.

American Association Of Clinical Endocrinologists And American College Of Endocrinology 2016 Outpatient Glucose Monitoring Consensus Statement

“…Contaminants on the skin from food sources (fruits, juices, sodas, milk) and even hand lotions can artificially raise capillary blood glucose levels and potentially lead to an overdose of insulin with subsequent hypoglycemia. Acetaminophen is well-known to result in spurious values in CGM systems (15,44,56,164,165). Physical compression of the CGM sensor during sleep can result in seriously low glucose readings.…”

Intraperitoneal Glucose Sensing is Sometimes Surprisingly Rapid

“…While intraarterial (IA) and intravenous (IV) measurements are not practically usable in outpatients, subcutaneous (SC) sensing has become the standard for continuous glucose monitoring (CGM) during the last 15 years. However, state of the art SC glucose sensing technologies with enzyme-based amperometric technology still face challenges with time delays and slow dynamics (Basu et al, 2013;Cengiz and Tamborlane, 2009;Boyne et al, 2003;Davey et al, 2010) as well as poor robustness (Helton et al, 2011;Mensh et al, 2013), even though recent publications indicate that novel CGM systems may be less prone to such problems (Garcia et al, 2013;Bailey et al, 2015). These challenges originate partly from the sensor technology and partly from the physiologically slow glucose transfer between intravascular glucose levels and glucose levels in subcutaneous tissue.…”

“…by Burnett et al (2014)). Additionally, an IP sensor location may be less prone to mechanical disturbances (Helton et al, 2011;Mensh et al, 2013), variation due to fluctuation in tissue perfusion (Cengiz and Tamborlane, 2009;Burnett et al, 2014;Stout et al, 2004) and temperature effects as the body core temperature is strictly regulated. Thus, based on previous animal studies, the peritoneal cavity is a promising alternative location for continuous glucose sensing (Burnett et al, 2014;Clark et al, 1987Clark et al, , 1988Velho et al, 1989).…”

Nonadjunctive Use of Continuous Glucose Monitoring for Diabetes Treatment Decisions

“…If a person enters an erroneous reference capillary blood glucose (CBG) value, if their fingertip has sugar or syrup on it for example, this error will artificially increase the CBG and can interject significant error into a CGM system, 10 whereas compression of the sensor site, such as lying on sensor during sleep, can cause artificially low signals. 11 Sensor drift, which can artificially increase or decrease the sensor value, is incompletely understood. Sensor drift relates to the foreign body response bringing inflammatory cells to the sensor insertion cite, resulting in drift of the sensor signal possibly from these cells consuming oxygen and glucose as well as producing compounds such as hydrogen peroxide.…”