New Techniques for Real-Time Microsleep Assessment

SUMMARY SignificanceImpaired alertness accompanied by short microsleep events is a frequently reported phenomenon in all areas of modem lifeA microsleep event can be defined as a somewhat unexpected short episode of sleepbetweenandsecondsthat occurs in the midst of ongoing wakeful activityPeople who experience microsleeps usually remain unaware of theminstead believing themselves to have been awake the whole timeIt is suspected that such microsleep events are responsible for many accidents on the road and in the workplaceMicrosleeps become extremely dangerous when occurring during situations which demand continuous alertnesssuch as driving a motor vehicle or operating heavy machineryMicrosleep has a massive impact on health and safetyTodayandapos s toll of approximatelypolice reported highway crashes with estimates offatalities annually identified as having driver drowsiness fatigue as principal casual factorsThe onset of microsleep remains difficult to detect in real life settingsA used measure of drowsinessso called `PERCLOSandaposthe percentage of time a personandapos s eyes areclosed over a period of timetypically five minutesAs suchit may detect only the very late stages of drowsiness and cannot timely detect onset of this dangerous subset of drowsy individualsIn this application we propose novel nondisruptive and nonintrusive technique to measure eyelid dynamic movement via assessment of related changes in the radio frequency of a very weak and totally harmless electromagnetic field created in the vicinity of the eyelidsPreliminary DataInitial realization of this measurement technique was successfully demonstrated with the support from an award of National Science FoundationNSFfor the projectFatigue Measurement InstrumentThe sensor created in that project included as a resonatorfew turns of Teflon coated very thin wire clipped to a frame resembling eyeglasses and connected to novel Eddy Current Inductance to Digital Converter LDCmicrochip of Texas InstrumentSuch very inexpensivecost well below $highresolution impedance measurement sensor could be wornfor exampleas part of the required safety glasses in mining fieldfor a daylong assessment and recording of eyelid movement at any workplace without any interfering with an operatorandapos s everyday activitySpecific AimsDevelop signal analysis SW package for calculation of directly related to microsleep detection ocular variablesAmplitude Velocity Ratioi ethe ratio of the maximum amplitude to maximum velocity of eyelid movement for the reopening phase of blinksPercent Long ClosuresLCproportion of time eyes are fully closedDuration of Ocular QuiescenceDOQAll these eyelid movement parameters will be measured during vigilance tasks following restricted sleep and a rested state to compare the measures to Oxford Sleep ResistanceOSLERtest at the Attention and Performance Lab of Washington University at StLouis The novel non disruptiveprecise technique for monitoring of eyelid dynamic movements for timely microsleep detection would serve as an alternative to and an apparent refinement of the existing PERCLOS metric for prolonged precise and non intrusive measurement without interference with operator daily activityThis project ought to lead to development of novel technology for monitoring operator alertness drowsiness mission critical personnel in civil and military operations