Researchers give greenlight for blood pressure measurement

A device for measuring blood pressure accurately without using the potentially harmful metal mercury has been developed by a team of researchers at Newcastle University and the city’s Freeman Hospital.

Instruments containing mercury have already been banned from use in hospitals by several countries because of the potential danger to staff and patients if an instrument breaks.

The team of researchers was led by Professor Alan Murray of the Regional Medical Physics Department, which is based at the Freeman Hospital in Newcastle upon Tyne. He says the device, called ‘Greenlight 300’, is the first practical and accurate non-mercury blood pressure measurement device for clinical use.

The new device uses a silicon chip sensor device to take a pressure reading but is called greenlight 300 because it displays the results on a large, easy to read, circular instrument display of green LEDs. Clinicians can operate it in the same way as a mercury sphygmomanometer, by placing a cuff around the patient’s arm and inflating it to take a reading, and listening for sounds through a stethoscope.

The Government’s Medical Devices Agency has said the future of clinical devices containing mercury is uncertain. It points out that some European countries have imposed bans on clinical devices containing mercury, and also that at least one British hospital has decided to replace its mercury sphygmomanometers following concerns over the level of exposure to its staff.

Controls on the exposure to mercury are also imposed on hospitals by the Health and Safety Executive, as part of the Control of Substances Hazardous to Health Regulations (COSHH).

If mercury is released into the environment, it could contaminate the food chain, and direct exposure to mercury is also a risk if the vapour is inhaled or absorbed through the skin.

The mercury sphygmomanometer has served the medical profession over the last 100 years and is regarded as the ‘gold standard’ for measuring blood pressure.

Various automatic devices, which dispense with the clinician’s skilled observations by stethoscope, are being used in an attempt to replace the mercury equipment following concerns about safety but there have been concerns about the accuracy of these.

Professor Alan Murray said: ‘Making Greenlight 300 available to clinicians as an alternative to the mercury sphygmomanometer is a great breakthrough. This is especially true when considering the health and safety issues surrounding use of the mercury device.

‘Greenlight 300 is as accurate as the mercury blood pressure measuring equipment, and as far as I am aware it is the first device of its kind.’

The London medical devices manufacturer A C Cossor and Son has bought the rights to the device, in a deal brokered by Newcastle University’s Technology Transfer Office, and are making it commercially available.

JJ Electronics in Cramlington, Northumberland, have been awarded the contract to manufacture the electronic circuits of Greenlight 300.