Improving safety for intravenous infusion

Intravenous infusions are ubiquitous in medical practice and an estimated 15 million administration sets will be used within the UK this year. Every time an intravenous access device is used, the potential for air embolism is present. This is particularly true when using pressurised infusion devices or central venous access; the risks of air embolism are increased in paediatric practice and in the presence of venoarterial shunting. The Department of Health has included air embolism in its ‘never events’ list for 2011-12,1 and air embolism is the subject of extensive practice guidance in documents such as the Royal College of Nursing’s Standards for Infusion Therapy 2010.2 It has been recommended that air-inline detectors should be used to monitor for air bubbles in administration sets when delivered via a volumetric infusion device.3,4 These are commonplace at ward level, but in anaesthesia and in acute care settings, where infusions are subject to constant alterations under direct clinical supervision, gravity and pressure administration sets lacking air-in-line detectors are routine. The potential for air embolism here is high, with frequent changes of infusion container and, in particular, the unique problems of rigid containers for a number of infusates such as intravenous paracetamol, propofol and human albumin solution. These pose a problem as air must be allowed to enter the container for the fluid to empty – either through a specially designed air inlet or a modified chamber spike, and, if staff are not vigilant, large quantities of air can be entrained into the intravenous line. Pressure driven sets can rapidly infuse this air intravenously, but even if detected before the air enters the patient, removal of the air requires time, distracts staff, and commonly leads to increased threat to line sterility by recurrent disconnection. Faced with this problem, two clinicians, Graham Bell and James Limb, at the Royal Hospital for Sick Children in Glasgow, collaborated with the Glasgow School of Art Product Design Engineering Department. The process began with a project proposal, a simple definition of a physical issue that causes a problem, which was submitted for consideration by the final year BSc and MSc undergraduates. Ian Guy took on the brief, and we have worked together on the project since. The value of working across professional boundaries cannot be overstated here, with the clinicians bringing the knowledge of the problems, limitations within clinical practice, and insight into the practicalities of intravenous infusions, and the engineer bringing the development resources, materials and manufacturing knowledge and, through the University, a wealth of resources for the development of the project. The project started with an introduction to the problem of air entrainment for Ian, and a series of meetings with health professionals including anaesthetists, nurses and perfusionists. While Ian returned to the lab, we completed audits of bubble entrainment into IV lines, and found insights into real life scenarios – such as drip chambers frequently hanging offvertical. In the lab, dissecting administration sets, a test rig was built to observe the physical behaviour of entrained air in an IV line. Fundamental to this problem was the observation that air in a drip line does not behave like bubbles of air in the sea, for example, and that the dynamic interplay of surfacetension, bubble-size, flow and buoyancy all affect bubble behaviour. This research demonstrated a number of potential mechanisms of entrainment; the largest volumes of entrained air resulted from rigid fluid containers running dry, and this became the focus of our development. At each stage of development, feedback from end users was of utmost importance, but this information was also coupled with advice from stakeholders in the design, such as manufacturing, engineering and business professionals, with the aim of selecting the solution which was best suited to the user but also commercially viable. The design we proceeded with was the development of a small floating seal, which, unlike traditional float-balls in some drip chambers, made use of an elastic sealant. This flexible fin-like membrane was later to be the key to the patent application as this, rather than the solid bung, isolated the IV line from the atmosphere. Over 30 prototypes varied the materials and geometry of the fin, float and cone. The final design incorporates a float with deformable silicone seal; this isolates the chamber as the fluid level falls. When the chamber is re-primed, the float is disengaged by squeezing the chamber exit, and the line can be used again. The float also provides a novel visual warning system, which indicates whether the fluid is infusing or the infusate container is empty and needs to be replaced, giving a rapid visual prompt as to the infusion status. Existing solutions on the market are limited in the range of infusates that they are effective with. Air Free, however, ofters a fluid independent, low-cost solution which functions with almost no change to existing staff practice. In addition, the visual warning aims to minimise disruption to patient drug supply. The chamber is backwardscompatible with the full range of gravity and pump administration sets, working to prevent air entrainment in all clinical situations.

Proof of concept

The device has successfully passed a proof of concept phase to verify the technical function of the plug, and has been shown in non-clinical testing to be effective in providing a seal at flow rates from 5 to 999 mL/hr using water, crystalloids and colloids. A high-fidelity prototype of the full assembly is now underway, using CNC milling, vacuum casting and OEM sheet silicone to build the various components. Once completed this prototype will be used to verify the visual warning system as well as test the full assembly in a variety of clinical scenarios (patient transfer, infusate changes etc.). This prototype will also be used to generate marketing materials for the product, and in demonstrations at trade shows/pitches. The device has been successful in various national and international competitions, being joint winner of the Association of Anaesthetists of Great Britain and Ireland’s inaugural Innovation in Anaesthesia and Critical Care Award 2012, winner of the Scottish Institute for Enterprise’s New Ideas competition 2010, finalist in the international James Dyson Award 2010, and finalist in the John Logie Baird Young Innovator 2011 and Scottish Enterprise Life Sciences awards 2012. We believe this innovation has the potential to become a universal drip chamber for intravenous crystalloids, colloids and blood products, and are actively seeking a sponsor and manufacturer who would be willing to take the future development of this innovation forward.