CONNECT challenges: towards emergent connectors for eternal networked systems

The CONNECT European project that started in February 2009 aims at dropping the interoperability barrier faced by today’s distributed systems. It does so by adopting a revolutionary approach to the seamless networking of digital systems, that is, synthesizing on the fly the connectors via which networked systems communicate.

Needleless connectors:the way forward in the prevention of catheter-related infections?

Letter to the Editor

Run-time connector synthesis for autonomic systems of systems

A key objective of autonomic computing is to reduce the cost and expertise required for the management of complex IT systems. As a growing number of these systems are implemented as hierarchies or federations of lower-level systems, techniques that support the development of autonomic systems of systems are required. This article introduces one such technique, which involves the run-time synthesis of autonomic system connectors. These connectors are specified by means of a new type of autonomic computing policy termed a resource definition policy, and enable the dynamic realisation of collections of collaborating autonomic systems, as envisaged by the original vision of autonomic computing. We propose a framework for the formal specification of autonomic computing policies, and use it to define the new policy type and to describe its application to the development of autonomic system of systems. To validate the approach, we present a sample data-centre application that was built using connectors synthesised from resource-definition policies.

The source, cost and prevention of central venous catheter-related infection

Central venous catheters have become an integral part of patient management however they are associated with many complications including infection. Despite efforts being made to reduce the incidence of such infect ions the problem continues to increase and has resource implications for the Health Service. Studies relating to the source of microorganisms causing CVC-associated infection, the cost of such infections and the efficacy of an antimicrobial catheter have been undertaken. Thirty patients who required a CVC as part of their medical management and underwent cardiac surgery had the distal tips of their catheters sampled whilst in situ. Sampling took place within 1 h of catheter placement. Bacteria were isolated from 16% of the catheter distal tips sampled in situ. The guidewires used to insert the devices were also contaminated (50%). When CVC were inserted via a protective sheath, avoiding contact with the skin. the incidence of microbial contamination was reduced. These findings suggest that despite rigorous skin disinfection and strict aseptic technique, viable microorganisms are impacted onto the distal tip of CVC during the insertion procedure. Needleless intravascular access devices have been introduced in order to reduce the incidence of need1estick injury. However, it was unclear whether such connectors would act as a portal of entry for microorganisms to CVC. The efficacy of these devices was investigated. Within the controlled laboratory environment it was demonstrated that needleless devices, when challenged with microorganisms, did not allow the passage of microbes when flu id was injected. This therefore suggested that the devices should not increase the risk of catheter colonisation. When used in clinical practice however microbial contamination of the needleless connectors was 55 % in comparison to the routinely used luer connectors (23%). The cost of infections associated with CVC was determined. Twenty patients catheterised with a CVC designed for long term use who were admitted to hospital with a presumptive diagnosis of catheter-related infection were studied. The treatment given specifically for this infection was costed. The mean cost of such an infection was £ 1781.81. Throughout the UK this may amount to £1.565.906 per annum. The cost of infections associated with CVC designed for short term use was estimated to be between 5 and 7 million pounds per annum in the UK. In an attempt to reduce both the incidence and cost of catheter- related infection antimicrobial CVC have been developed. The efficacy of a novel polyurethane CVC impregnated on both the internal and external catheter surface with the quaternary ammonium compound benzalkonium chloride was investigated. Eighty eight patients received an antimicrobial catheter and 78 patients a conventional polyurethane CVC. The anti-microbial CVC resulted in a reduction in microbial colonisation of the external and internal polymer surfaces as compared to the control device. The observed reduction in microbial colonisation with the anti-microbial CVC may decrease the likelihood of subsequent infection offering a useful approach to the prevention of catheter-related infections.

Vibration analysis of a printed circuit board

The reliability of the printed circuit board assembly under dynamic environments, such as those found onboard airplanes, ships and land vehicles is receiving more attention. This research analyses the dynamic characteristics of the printed circuit board (PCB) supported by edge retainers and plug-in connectors. By modelling the wedge retainer and connector as providing simply supported boundary condition with appropriate rotational spring stiffnesses along their respective edges with the aid of finite element codes, accurate natural frequencies for the board against experimental natural frequencies are obtained. For a PCB supported by two opposite wedge retainers and a plug-in connector and with its remaining edge free of any restraint, it is found that these real supports behave somewhere between the simply supported and clamped boundary conditions and provide a percentage fixity of 39.5% more than the classical simply supported case. By using an eigensensitivity method, the rotational stiffnesses representing the boundary supports of the PCB can be updated effectively and is capable of representing the dynamics of the PCB accurately. The result shows that the percentage error in the fundamental frequency of the PCB finite element model is substantially reduced from 22.3% to 1.3%. The procedure demonstrated the effectiveness of using only the vibration test frequencies as reference data when the mode shapes of the original untuned model are almost identical to the referenced modes/experimental data. When using only modal frequencies in model improvement, the analysis is very much simplified. Furthermore, the time taken to obtain the experimental data will be substantially reduced as the experimental mode shapes are not required.In addition, this thesis advocates a relatively simple method in determining the support locations for maximising the fundamental frequency of vibrating structures. The technique is simple and does not require any optimisation or sequential search algorithm in the analysis. The key to the procedure is to position the necessary supports at positions so as to eliminate the lower modes from the original configuration. This is accomplished by introducing point supports along the nodal lines of the highest possible mode from the original configuration, so that all the other lower modes are eliminated by the introduction of the new or extra supports to the structure. It also proposes inspecting the average driving point residues along the nodal lines of vibrating plates to find the optimal locations of the supports. Numerical examples are provided to demonstrate its validity. By applying to the PCB supported on its three sides by two wedge retainers and a connector, it is found that a single point constraint that would yield maximum fundamental frequency is located at the mid-point of the nodal line, namely, node 39. This point support has the effect of increasing the structure's fundamental frequency from 68.4 Hz to 146.9 Hz, or 115% higher.

A randomized, prospective clinical trial to assess the potential infection risk associated with the PosiFlow® needleless connector

The microbial contamination rate of luers of central venous catheters (CVCs) with either PosiFlow® needleless connectors or standard caps attached was investigated. The efficacy of 70% (v/v) isopropyl alcohol, 0.5% (w/v) chlorhexidine in gluconate 70% (v/v) isopropyl alcohol and 10% (w/v) aqueous povidone-iodine to disinfect the intravenous connections was also assessed. Seventy-seven patients undergoing cardiac surgery who required a CVC as part of their clinical management were randomly allocated either needleless connectors or standard caps. Patients were also designated to receive chlorhexidine/alcohol, isopropyl alcohol or povidone-iodine for pre-CVC insertion skin preparation and disinfection of the connections. After 72 h in situ the microbial contamination rate of 580 luers, 306 with standard caps and 274 with needleless connectors attached, was determined. The microbial contamination rate of the external compression seals of 274 needleless connectors was also assessed to compare the efficacy of the three disinfectants. The internal surfaces of 55 out of 306 (18%) luers with standard caps were contaminated with micro-organisms, whilst only 18 out of 274 (6.6%) luers with needleless connectors were contaminated (P<0.0001). Of those needleless connectors disinfected with isopropyl alcohol, 69.2% were externally contaminated with micro-organisms compared with 30.8% disinfected with chlorhexidine/alcohol (P<0.0001) and 41.6% with povidone-iodine (P<0.0001). These results suggest that the use of needleless connectors may reduce the microbial contamination rate of CVC luers compared with the standard cap. Furthermore, disinfection of needleless connectors with either chlorhexidine/alcohol or povidone-iodine significantly reduced external microbial contamination. Both these strategies may reduce the risk of catheter-related infections acquired via the intraluminal route. © 2003 The Hospital Infection Society. Published by Elsevier Science Ltd. All rights reserved.

A prospective clinical trial to evaluate the microbial barrier of a needleless connector

Needleless connectors are being increasingly used for direct access to intravascular catheters. However, the potential for microbial contamination of these devices and subsequent infection risk is still widely debated. In this study the microbial contamination rate associated with three-way stopcock luers with standard caps attached was compared to those with Y-type extension set luers with Clearlink® needleless connectors attached. Fifty patients undergoing cardiothoracic surgery who required a central venous catheter (CVC) as part of their peri- and postoperative management were studied for microbial contamination of CVC luers following 72 hrs in situ. Each patient's CVC was randomly designated to have either the three-way stopcocks with caps (control patients) or Clearlink® Y-type extension sets (test patients). Prior to, and following each manipulation of the three-way stopcock luers or Clearlink® devices, a 70% (v/v) isopropyl alcohol swab was used for disinfection of the connections. The microbial contamination of 393 luers, 200 with standard caps and 193 with Clearlink® attached, was determined. The internal surfaces of 20 of 200 (10%) three-way stopcock luers with standard caps were contaminated with micro-organisms whereas only one of 193 (0.5%) luers with Clearlink® attached was contaminated (P < 0.0001). These results demonstrate that the use of the Clearlink® device with a dedicated disinfection regimen reduces the internal microbial contamination rate of CVC luers compared with standard caps. The use of such needle-free devices may therefore reduce the intraluminal risk of catheter-related bloodstream infection and thereby supplement current preventive guidelines. © 2006 The Hospital Infection Society.