Effect of infusion rate and indwelling time on tissue resistance pressure in small-volume subcutaneous infusion like in continuous subcutaneous insulin infusion.

BACKGROUND: To deliver exact volumes of liquid subcutaneously (e.g., during continuous subcutaneous insulin infusion [CSII]), the insulin pump has to overcome not only frictional losses of the mechanical drive and pressure losses in the tubing and infusion set, but also the tissue resistance pressure (TRP). Up to now, detailed information about the dependence of TRP on volumes and delivery rates common for CSII is missing. However, knowledge of the typical range of TRP during CSII is important to optimize occlusion detection and the design of insulin pumps. MATERIALS AND METHODS: TRP was examined in 24 subjects (12 patients with type 1 diabetes mellitus and long-term CSII therapy and 12 subjects without diabetes) while subcutaneously infusing a liquid test solution via infusion sets with 8-mm steel cannulas using four different infusion rates (infused volume, 0.3 mL of saline solution). The primary objectives were to estimate the TRP and its dependence on the infusion rate, as well as the impact of the cannula indwelling time of roughly 80 h. RESULTS: Stepwise increases in the infusion rate were associated with significant rises in median TRP: 0.01 mL/min (= 1 U/min for U100 insulin), 8.09 mbar; 0.05 mL/min, 18.28 mbar; 0.1 mL/min, 25.18 mbar; and 0.5 mL/min, 62.59 mbar. No statistically significant changes in TRP could be attributed to the catheter indwelling time of roughly 80 h. CONCLUSIONS: Median TRP increased significantly with higher infusion rates. Catheter indwelling time had no significant effect on the TRP. Occlusion detection may be improved by using rate-dependent detection thresholds.

Feasibility of overnight closed-loop control based on hourly blood glucose measurements.

INTRODUCTION: Safe and effective closed-loop control (artificial pancreas) is the ultimate goal of insulin delivery. In this study, we examined the performance of a closed-loop control algorithm used for the overnight time period to safely achieve a narrow target range of blood glucose (BG) concentrations prior to breakfast. The primary goal was to compare the quality of algorithm control during repeated overnight experiments. MATERIALS AND METHODS: Twenty-three subjects with type 1 diabetes performed 2 overnight experiments on each of three visits at the study site, resulting in 138 overnight experiments. On the first evening, the subject's insulin therapy was applied; on the second, the insulin was delivered by an algorithm based on subcutaneous continuous glucose measurements (including meal control) until midnight. Overnight closed-loop control was applied between midnight and 6 a.m. based on hourly venous BG measurements during the first and second nights. RESULTS: The number of BG values within the target range (90-150 mg/dl) increased from 52.9% (219 out of 414 measurements) during the first nights to 72.2% (299 out of 414 measurements) during the second nights (p < .001, χ²-test). The occurrence of hypoglycemia interventions was reduced from 14 oral glucose interventions, the latest occurring at 2:36 a.m. during the first nights, to 1 intervention occurring at 1:02 a.m. during the second nights (p < .001, χ²-test). CONCLUSIONS: Overnight controller performance improved when optimized initial control was given; this was suggested by the better metabolic control during the second night. Adequate controller run-in time seems to be important for achieving good overnight control. In addition, the findings demonstrate that hourly BG data are sufficient for the closed-loop control algorithm tested to achieve appropriate glycemic control.

Evaluation of an alternative chest physiotherapy method in infants with respiratory syncytial virus bronchiolitis.

BACKGROUND: We proposed a new chest physiotherapy (CPT) secretion clearance method to treat respiratory syncytial virus bronchiolitis in infants. Our new CPT method consists of 15 prolonged slow expirations, then 5 provoked cough maneuvers. METHODS: We randomized 20 infants (mean age 4.2 months) into 2 groups: 8 patients received 27 sessions of nebulization of hypertonic saline; 12 patients received 31 sessions of nebulization of hypertonic saline followed by our new CPT method. We used the Wang clinical severity scoring system (which assesses wheezing, respiratory rate, retractions, and general condition) and measured S(pO(2)) and heart rate before each CPT session (T0), immediately after the 30-min session (T30), and 120 min after the session (T150). RESULTS: Within the groups: in the first group, Wang score was significantly lower at T150 than at T0: 4.6 vs 5.0 (P = .008). In the new-method-CPT group, Wang score was significantly lower at T30 (3.6 vs 4.3, P = .001) and at T150 (3.7 vs 4.3, P = .002). Wheezing score was significantly lower at T150 than at T0 (1.1 vs 1.2, P = .02) in the first group, and in the new-method-CPT group at T30 than at T0 (0.8 vs 1.3, P = .001) and at T150 than at T0 (0.9 vs 1.3, P = .001). Between the groups: at T30 the improvement was significantly better in the new-method-CPT group for overall Wang score (P = .02), retractions (P = .05), respiratory rate (P = .001), and heart rate (P < .001). At T150 the Wang score was not significantly different between the groups. At T30 (versus T0) the difference in percent gain between the groups was significant for Wang score (P = .004), wheezing (P = .001), and heart rate (P = .02). Over 5-hospital days, the daily baseline (T0) Wang score decreased significantly in the new-method-CPT group (P = .002), whereas it did not in the first group. There were no adverse events. Average hospital stay was not significantly different between the groups. CONCLUSIONS: Our new CPT method showed short-term benefits to some respiratory symptoms of bronchial obstruction in infants with acute respiratory syncytial virus bronchiolitis.

The INCA system: a further step towards a telemedical artificial pancreas.

Biomedical engineering research efforts have accomplished another level of a "technological solution" for diabetes: an artificial pancreas to be used by patients and supervised by healthcare professionals at any time and place. Reliability of continuous glucose monitoring, availability of real-time programmable insulin pumps, and validation of safe and efficient control algorithms are critical components for achieving that goal. Nevertheless, the development and integration of these new technologies within a telemedicine system can be the basis of a future artificial pancreas. This paper introduces the concept, design, and evaluation of the "intelligent control assistant for diabetes, INCA" system. INCA is a personal digital assistant (PDA)-based personal smart assistant to provide patients with closed-loop control strategies (personal and remote loop), based on a real-time continuous glucose sensor (Guardian RT, Medtronic), an insulin pump (D-TRON, Disetronic Medical Systems), and a mobile general packet radio service (GPRS)-based telemedicine communication system. Patient therapeutic decision making is supervised by doctors through a multiaccess telemedicine central server that provides to diabetics and doctors a Web-based access to continuous glucose monitoring and insulin infusion data. The INCA system has been technically and clinically evaluated in two randomized and crossover clinical trials showing an improvement on glycaemic control of diabetic patients.