This proposal describes the development of a 'Sensing ET Tube'. This device will replace the standard endotracheal (ET) tube used in anaesthesia and in ventilated intensive care patients and provide key vital signs monitoring utilising optoelectronic sensors. Continuous monitoring of patients' arterial oxygen saturation is essential during surgery, however pulse oximeters often misread or fail altogether as a result of peripheral vasoconstriction, hypotension or hypovolaemia. The Sensing ET Tube will allow continuous measurement of oxygen saturation and other parameters, such as pulse rate, from a single internal site, and will reduce the number of surface sensors placed on the skin and the number of electrical connections to the patient. The applicants have already developed similar sensor technology in the oesophagus and other internal locations. A pilot clinical evaluation of the device will be completed in anaesthetised patients undergoing surgery. The project will lead to further development of a multi-sensor tracheal platform for comprehensive anaesthesia and intensive care monitoring.

The aim of this project is to develop and evaluate a novel medical device known as the 'Sensing ET Tube' for measuring oxygen levels in patients undergoing surgical operations. The device replaces the standard breathing tube used in surgery and incorporates photonic sensors for measurement of the patient's oxygen level and other vital signs. Currently this information is supplied from finger probes, which can fail often, for example when the patient is cold or when the blood pressure is low. The new device is completely harmless and allows the anaesthetist to monitor the oxygen level from the central region of the body using minimal connections. If successful, future work is planned to incorporate other sensors into the system, providing a complete overview of the health of the patient. This will greatly simplify the process of patient monitoring while reducing the number of failures, improving patient safety and reducing operating costs.

A clinical trial is planned in up to 50 patients undergoing general anaesthesia, which will quantitatively evaluate the accuracy and reliability of the measured clinical variables and the device's expected performance in mainstream operation. This information will provide the basis for further commercial development, most likely through partnership with a medical device manufacturer.

To summarise, the main aims of the project are:

• Investigate photoplethysmographic signals from the human trachea and identify viability to measure heart rate, and blood oxygen saturation by comparison with "gold standard" techniques.
• Evaluate custom-designed endotracheal sensor for operation and determine ideal electrical characteristics for optimal operation (current supply, detector amplification etc.)

Inclusion Criteria:

• ASA I-III
• 18 Years and older
• Undergoing elective surgery requiring general anaesthesia, and endotracheal tube as part of their anaesthetic.

Exclusion Criteria:

• Those who refuse consent
• Known or potentially difficult airway
• Respiratory conditions including severe asthma, COPD, lung cancer etc.
• Pregnant women

all data is anonymised and raw signals are only shared among the named investigators