A cut above

Electrosurgery allows doctors to make precise incisions while limiting blood loss during operations. A high-frequency electric current is applied, effectively employing a series of sparks to generate heat, as a way of cutting or coagulating biological tissue.

But this long-established technology has the disadvantages of requiring a high voltage and exposing patients to electric currents during surgery, placing them at risk of burns, deep tissue damage caused by the sparks, and even death from such complications.

Now, an Oxfordshire-based firm has found a way of eliminating the need for electric currents by transferring the principles of plasma physics from space technology to medicine.

Plasma Surgical was founded in 1999 with the objective of advancing the surgical application of a patented neutral plasma technology. This stemmed from over a decade of original work carried out by Professor Nikolaj Suslov, professor of thermal and molecular physics at the Moscow Institute of Science and Technology, and his colleagues.

A plasma is a high energy gas which readily gives up its energy as heat and light. Gas plasmas have been used for many years in a variety of applications from cutting metals to rocket engines used to position satellites in space.

The Plasma Surgical team realised that they could use the electrically neutral plasma technology as a safe and precise means of coagulation. When applied to tissue, a high-energy beam of the plasma rapidly creates a very thin and flexible coagulation layer, preventing bleeding and lymphatic oozing. So the team began a project to develop a machine to generate and control a jet of plasma suitable for medical use, the PlasmaJet.

The technology uses a jet of argon plasma to provide fast and precise control of bleeding, leaving a wound sealed. It can be used during both conventional and keyhole surgery, greatly reducing the risk and duration of complex procedures and can minimize costs by reducing the patient’s stay in hospital.

PlasmaJet’s specification today is very different to its original one, having evolved considerably over the two-year project. It contains numerous technical complexities that have to work together without interfering with one other.

Electrical devices create electromagnetic energy and it is vital for medical products in particular to have a low electromagnetic compatibility (EMC) emissions profile. This means countermeasures have to be taken to reduce this energy and prevent it escaping into the environment.

To tackle this problem, Plasma Surgical turned to Wiltshire-based ML Electronics (MLE). The system design firm was able to use specialised techniques to create a new power supply for the PlasmaJet that can be plugged in anywhere in the world and is compliant with international specifications and regulations.

Once the device was electrically neutral, PlasmaJet became safe to use close to electronic devices like pacemakers, defibrillators and metallic implants. The device can also be used safely near sensitive tissue and anatomical landmarks like facial or spinal nerves and eyelids.

The PlasmaJet handpiece generates a gas jet at very high temperature so the internal electrodes need water-cooling. To prevent damage to the handpiece, the design originally made use of a mechanical flow switch, which blocked the plasma jet if water flow was insufficient.

The design team decided to make the waterflow adjustable, which would allow for future product developments. MLE created a very simple waterflow sensor based on an analogue pressure transducer. This has no moving parts and allows an appropriate critical flow setting to be created in software specifically for PlasmaJet’s handpiece, but which can be adapted for any product variations.

The waterflow sensor was suggested by MLE as an alternative to an expensive off-the-shelf item and the original mechanical flow switch. The company was able to design the waterflow sensor from scratch, which optimised the PlasmaJet’s performance and was also a more economical solution.

The PlasmaJet console contains three embedded processors, the largest of which is responsible for the user interface, controls, indicators and the control of plasma generation. The power supply has two smaller processors, one controlling the mains side sequencing and the other controlling the temperature and ignition of the plasma.

As PlasmaJet moves into production to meet worldwide demand, MLE are continuing to work with Plasma through offering supported manufacture. The PlasmaJet ’s design is so complex, with so many components that it will continue to need support throughout its life, with requirements for upgrades, repairs and design changes to overcome component obsolescence.

The two companies have been able to take the original concept for the PlasmaJet and make it suitable for commercial implementation. MLE has provided close support to Plasma Surgical, which has allowed the firm to obtain approval from the US Food and Drug Administration (FDA) for the PlasmaJet and open an additional manufacturing facility in Georgia last year.

In clinical trials the PlasmaJet has already contributed to successful operations on over 170 patients, many of whom were able to leave hospital several days earlier than expected.