The Sensing Endotracheal Tube

Abstract

Current pulse oximetry sensors are not very wellsuited to use in anaesthetised patients as it has been shownthat during episodes of reduced peripheral circulation they donot function correctly or fail all together [1], [2]. To addressthis problem a new design for a photoplethysmography (PPG)endotracheal (ET) sensor to monitor pulse rate and oxygensaturation (SpO2) internally is presented. Flexible printedcircuit board (PCB) technology and miniature optoelectroniccomponents have been implemented and integrated with acustom instrumentation system [3]. The sensor adheres andconforms to the curvature of standard french-gauge 7 and 8ET tubes at the point just above the inflatable cuff within thelaryngeal positioning markings. A 3D-modelled, optically clear,soft silicon encapsulation electronically and thermally isolatesthe electronic components whilst providing a smooth surface toaid the insertion on the ET tube during standard intubationprocedures. A pilot study with 5 patients (3 Female, 2 Male),undergoing abdominal and limb laproscopic procedures hasdemonstrated the operation of the sensing ET tube, showinggood quality red and infra-red PPG signals. Preliminary signalanalysis reveals heart rate can be measured via PPG success-fully, with saturation (SpO2) readings in close agreement withthe commercial monitors of 97.9% (STD 0.2%) and 98.6% (STD 0.8%) respectivel