Airway maintenance device

An apparatus comprising:

• an airway maintenance device comprising an airway lumen having a proximal end and a distal end, and a distal end portion comprising an inflatable cuff incorporating an optical sensor configured to measure capillary blood flow rate in tissue surrounding the distal end when in position within a patient's airway, wherein the optical sensor comprises a portion of an optical fibre extending to the distal end portion along the lumen;
• and
• a control unit connectable to the optical sensor, the control unit configured to determine a measure of the capillary blood flow rate from a signal received from the optical sensor, wherein the control unit comprises:
• a light source configured to transmit light along the optical fibre to the optical sensor;
• and
• a light detector configured to measure light received in the signal from the optical sensor along the optical fibre,
• the control unit being configured to determine the measure of the capillary blood flow rate from an intensity of light received from the optical sensor.