A young Irish engineer has proved the feasibility of an improved method for administering anaesthesia, after her investigation of tissue bioimpedance using a macro-needle for biomedical applications
Bio

 

Patient safety is the key concern in the development of a ‘smart’ needle to be used for the administration of anaesthesia. By providing the administering clinician with electrical impedance data from different tissue types, they will be able to identify the needle’s real-time location and delivery point. This is crucial to ensure that the agent is not administered to nerve bundles, which could cause long-term or permanent nerve injury.

The research project was initiated when Dr Brian O’Donnell, consultant anaesthetist in Cork University Hospital (CUH), approached the Tyndall National Institute in search of a solution to this real clinician problem. Tyndall is a partnership between University College Cork (UCC), Science Foundation Ireland (SFI) and the Department of Enterprise, Trade and Employment.

It is one of Europe’s leading research centres in Information and communications technology research and development and the largest facility of its type in Ireland. Thus began the collaboration with Dr Eric Moore, of the Life Science Group at Tyndall, on developing the ‘smart’ needle concept.

CONCEPT INTO WORKING REALITY

Lisa Helen

To demonstrate the feasibility of the concept, Dr O’Donnell was able to secure funding through the SFI-funded National Access Programme at Tyndall. The project was then advanced when further funding was granted to Dr Moore through the new SFI/Enterprise Ireland Technology Innovation Development Award programme.

Three years after the collaboration started, Lisa Helen took on the project, giving it a new impetus and driving it forward, with the intension to convert the ‘smart’ needle concept into a working reality. Helen is a graduate of UCC/Cork Institute of Technology and is currently a PhD candidate at Tyndall.

Working with her supervisors and another PhD candidate, Walter Messina – also of the Life Science Interface Group at Tyndall – her research has sought to satisfy the unmet need for a more accurate and more sensitive identification of the target nerve, as well as providing real-time guidance of the needle toward the nerve. The ‘smart’ needle will greatly improve the safety of a process known as ultrasound-guided peripheral nerve block (USgPNB).

The technique of USgPNB refers to a set of medical procedures which facilitate surgical operations and can also treat acute or chronic pain. The location of the needle tip relative to the target nerve is crucial to the safe and effective practice of USgPNB.

Fig 1: Nerve structure and (below)
Fig 2: Ultrasound image

Currently, USgPNB poses two important problems that this research aims to resolve:

1. The inability of ultrasound to identify epineurium (nerve covering, refer to Fig. 1), and thereby minimise the risk of harmful intraneural injection; and

2. A limitation of tools and resources available for effective training of anaesthetists in a new procedure. Extensive training is required to identify the components of an ultrasound image (Fig. 2). 

The use of USgPNB has increased dramatically worldwide over the past five years and it is now a core element of all higher specialist training programmes internationally. This growth in adoption reflects the clear benefits to the patient and the healthcare environment when nerve block is used instead of general anaesthesia for a wide number of surgical procedures. The introduction of a ‘smart’ needle would significantly reduce the training time and the costs incurred for the clinician and hospital respectively, limiting the shortcomings of the procedure.

BIOIMPEDANCE

While the construction of the smart needle is currently under way, in order to prove that the concept is feasible, a ‘macro-needle’ was initially constructed to measure bioimpedance of different tissues in meat samples. In biomedical engineering, bioimpedance is the response of a living organism to an externally applied electric current. It is a measure of the opposition to the flow of that electric current through the tissues, the opposite of electrical consuctivity. All cells have different electrical properties that result in the creation of a tissue-specific bioimpedance profile.

The capacity of a tissue to carry or impede current, and the magnitude of this capacity, depends on the composition of that tissue i.e. ion concentration, water/electrolyte content. Pork, lamb and beef samples were analysed using the ‘macro-needle’ connected to an impedance analyser (Zahner IM6) and a bioimpedance profile for fat, muscle and connective tissue was recorded in each meat over a frequency range of 100 Hz – 1 MHz during a two-minute test period, with recordings made every second seconds.

This is referred to as a frequency sweep. The range between 10 kHz – 100 kHz was identified as the optimum frequency range for the measurement of samples at both 120C and 370C.

Fig 3: Macro-needle used for bioimpedance analysis

This revealed that bioimpedance was inversely proportional to temperature. Further investigations into muscle, fat and connective tissue were performed at 30 kHz, 50 kHz and 70 kHz, demonstrating significant order of magnitude of separation between all three of the sample types.

These results allowed the determination of bioimpedance ranges for each tissue. The possibility of using bioimpedance to differentiate between tissues was demonstrated successfully during this study, supporting the concept of the ‘smart’ needle for USgPNB. This experiment will be repeated using the ‘smart’ needle once fabrication is complete.

Helen’s excellent research has been recognised both nationally and internationally.

She was nominated to compete in the President’s Prize competition at the Academy of Medical Laboratory Science annual conference, Biomedica 2014, in the RDS in Dublin. Helen presented her talk entitled, ‘Investigation of Tissue Bioimpedance using a Macro-needle for Biomedical Applications’. Competing against the best of her peers from around the country, her project was awarded second place and was highly commended for its innovative and original approach.

This prestigious prize was closely followed by the European Technology Platform on Smart Systems Integration’s announcement that Helen had won its ‘Best Poster Award 2014’ for ‘Development of a ‘smart’ needle integrated with an impedance sensor to determine nerve proximity for nerve blocking (anaesthetic) procedures’. She has been invited to speak at the Smart Systems Integration Conference in March, 2015.

Lisa Helen is a PhD student at Tyndall National Institute and the Department of Chemistry at UCC. She graduated from Cork Institute of Technology in 2012 with a Distinction in BSc Biomedical Science, for which she was awarded ‘Best Student’ sponsored by Sigma-Aldrich. She graduated from a joint BSc (Hons) degree between UCC and CIT with 1st Class Honours. She secured the Government of Ireland Postgraduate Scholarship from the Irish Research Council to fund her PhD studies. 

http://www.engineersjournal.ie/wp-content/uploads/2014/07/Anaesthetic-1024x683.jpghttp://www.engineersjournal.ie/wp-content/uploads/2014/07/Anaesthetic-300x300.jpgDavid O'RiordanBiohealthcare,SFI,Tyndall National Institute,UCC
  Patient safety is the key concern in the development of a ‘smart’ needle to be used for the administration of anaesthesia. By providing the administering clinician with electrical impedance data from different tissue types, they will be able to identify the needle’s real-time location and delivery point. This is...