Insulin induces a progressive increase in the resistance of subcutaneous tissue to fluid flow: Implications for insulin pump therapy.

AIM: To determine the effect of insulin on the resistance of subcutaneous tissue to the flow of infusion fluids. MATERIALS AND METHODS: Thirty subjects with type 1 diabetes wore two Accu-Chek Spirit Combo insulin pumps with Accu-Chek FlexLink infusion sets (Roche Diabetes Care, Mannheim, Germany) for 7 days. One pump was filled with insulin aspart (Novo Nordisk, Bagsvaerd, Denmark) and used for continuous subcutaneous insulin infusion (CSII). The other pump was filled with insulin diluting medium (IDM; Novo Nordisk) and used to deliver IDM subcutaneously at rates identical to those employed for CSII. Both infusion sites were assessed daily by measuring the pressure required to infuse various bolus amounts of IDM. RESULTS: On day 1, maximum pressure (Pmax ) and tissue flow resistance (TFR; calculated from measured pressure profiles) were similar for both infusion sites (P > 0.20). During the subsequent study days, the Pmax and TFR values observed at the IDM infusion site remained at levels comparable to those seen on day 1 (P > 0.13). However, at the site of CSII, Pmax and TFR progressively increased with CSII duration. By the end of day 7, Pmax and TFR reached 25.8 */2.11 kPa (geometric mean */geometric standard deviation) and 8.64 */3.48 kPa*s/µL, respectively, representing a remarkable 3.5- and 20.6-fold increase relative to the respective Pmax and TFR values observed on day 1 (P < 0.001). CONCLUSION: Our results suggest that insulin induces a progressive increase in the resistance of subcutaneous tissue to the introduction of fluid; this has important implications for the future design of insulin pumps and infusion sets.

Novel Single-Site Device for Conjoined Glucose Sensing and Insulin Infusion: Performance Evaluation in Diabetes Patients During Home-Use.

OBJECTIVE: This study evaluated a novel diabetes treatment device that combines commercially available continuous glucose monitoring and insulin infusion technology in such a way as to perform insulin delivery and glucose sensing through a single skin insertion site (single-port device). METHODS: Ten type 1 diabetes patients used the device for up to six days in their home/work environment for open-loop insulin delivery and glucose sensing. On an additional day, the device was used in combination with an algorithm to perform automated closed-loop glucose control under hospital settings. To assess the performance of the device, capillary blood glucose concentrations were frequently determined and a continuous glucose sensor was additionally worn by the patients. RESULTS: The average mean absolute relative deviation from blood glucose concentrations obtained for the sensor of the device was low (median, 13.0%; interquartile range, 10.5-16.7%; n = 10) and did not differ from that of the additionally worn glucose sensor (versus 13.9%; 11.9-15.3%; P = 0.922). Furthermore, insulin delivery with the single-port device was reliable and safe during home use and, when performed in combination with the control algorithm, was adequate to achieve and maintain near normoglycemia. CONCLUSION: Our data show the feasibility of open- and closed-loop glucose control in diabetes patients using a device that combines insulin delivery and glucose sensing at a single tissue site. SIGNIFICANCE: The reduction in device size and invasiveness achieved by this design may largely increase patient convenience and enhance acceptance of diabetes treatment with continuous glucose monitoring and insulin delivery technology.

Development of a Single-Site Device for Conjoined Glucose Sensing and Insulin Delivery in Type-1 Diabetes Patients.

OBJECTIVE: Diabetes patients are increasingly using a continuous glucose sensor to monitor blood glucose and an insulin pump connected to an infusion cannula to administer insulin. Applying these devices requires two separate insertion sites, one for the sensor and one for the cannula. Integrating sensor with cannula to perform glucose sensing and insulin infusion through a single insertion site would significantly simplify and improve diabetes treatment by reducing the overall system size and the number of necessary needle pricks. Presently, several research groups are pursuing the development of combined glucose sensing and insulin infusion devices, termed single-port devices, by integrating sensing and infusion technologies created from scratch. METHODS: Instead of creating the device from scratch, we utilized already existing technologies and introduced three design concepts of integrating commercial glucose sensors and infusion cannulas. We prototyped and evaluated each concept according to design simplicity, ease of insertion, and sensing accuracy. RESULTS: We found that the best single-port device is the one in which a Dexcom sensor is housed inside a Medtronic cannula so that its glucose sensitive part protrudes from the cannula tip. The low degree of component modification required to arrive at this configuration allowed us to test the efficiency and safety of the device in humans. CONCLUSION: Results from these studies indicate the feasibility of combining commercial glucose sensing and insulin delivery technologies to realize a functional single-port device. SIGNIFICANCE: Our development approach may be generally useful to provide patients with innovative medical devices faster and at reduced costs.