20 November 2007
Overcoming operative stress
Ceramic solves sensor challenge.
Despite the many improvements in surgical techniques, operations remain traumatic events.
“Virtually every patient undergoing surgery suffers from hypovolaemia –akin to severe dehydration,” explains Andy Mears, operations director for Deltex Medical. “This is because of the combined effects of preoperative starvation, the impact of the anaesthetic agents and trauma from the surgery itself. This leads to insufficient amounts of oxygen being delivered to the vital organs, which can cause medical complications – including peripheral and major organ failure.”
One technique which can be deployed to counter this problem is oesophageal Doppler technology and West Sussex based Deltex Medical is a market leader in this field. According to the company, numerous clinical studies have proven this technology to reduce the length of hospital stays by up to 40% across a range of surgical specialities.
Although Deltex has manufactured critical care devices for more than 20 years, it was looking for a partner who could design and manufacture a piezoceramic sensor for its CardioQ ultrasonic probe.
The oesophageal Doppler probe, which incorporates a transmitter and receiver, is used in conjunction with the Deltex’ CardioQ haemodynamic status monitor. The disposable probe is used to determine circulating blood volume – the amount of blood being pumped around the patient’s body during the operation.
Deltex became aware of Morgan Electro Ceramics from its work in the development of innovative medical devices, such as foetal heart monitors, and the two have worked together to establish which material would be best suited to the application.
“We worked closely with Morgan Electro Ceramics throughout the development of the product,” says Mears. “The company’s extensive knowledge of ceramics was a great benefit.”
Morgan Electro Ceramics recommended its PZT5H piezo ceramic material for its mechanical and electrical properties, specifically its high dielectric constant and sensitivity. “The sensor uses time of flight measurement of the travelling ultrasound wave to measure the blood flow,” explains Tony Beswick, general manager of Morgan Electro Ceramic.
The ceramic is fixed on the end of the probe – which has a diameter of approximately 5mm and is sleeved in a non toxic, latex free silicone rubber. It is inserted into the patient’s oesophagus, either orally or via the nasal route. Once in position, the transmitted signal rebounds off blood flowing in the descending aorta. The signal is received by another piezoelectric ceramic, which converts the ultrasonic pulses back into an electrical signal. In order to produce a minimally invasive device, the transmitter/receiver combination is made from a single piece of piezoceramic with wrap around electrodes. The received signal is then digitised and displayed into a real time waveform on the CardioQ display.
Using fluids and drugs, guided by the CardioQ, to optimise the amount of circulating blood volume reduces post operative complications allowing patients to make a faster, more complete, recovery and to return home earlier.
“Morgan Electro Ceramics manufactures the PZT ceramic and assembles the probe components itself on site,” says Mears. “This has enabled a more efficient manufacturing process and allowed us to optimise the supply chain.”
Other applications of ceramic in medical devices include ultrasonic imaging and high power transmitters of high frequency waves that assist with surgical cutting procedures such as cataract removal.
Author
Graham Pitcher
Supporting Information
Websites
http://www.deltexmedical.com
http://www.morganelectroceramics.com
Companies
Deltex Medical Ltd
Morgan Electro Ceramics
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