Singular Value Decomposition filtering, of vehicle component present in actograms recorded over moving platforms

JOSÉ GALLARDO; LEONARDO NICOLA SIRI; JOAQUÍN DIEZ; DANIEL E. VIGO

Congreso; III Latin American Federation of Biophysical Societies (LAFeBS) ? IX IberoAmerican Congress of Biophysics ? XLV Reunion Anual SAB 2016; 2016

Driving a ground bus is a complex task. Drivers drowsiness and fatigueimpair travel safety. Buses are drived by couples of bus-drivers, whichalternate each between driving and non-driving stages 2 hours length.The actigraphy quantifies body kinetic activity in an actogram, in timessupplemented with a Sleep Log compiled by the subject; actographsattached to the subject are used. In order to identify patterns of resting/ activity on the studied subjects, actograms can be analyzed manuallyby a blind expert or by computed algorithms. Currently, actograms are recorded on motionless platforms, because ofcontamination by vehicular signals (as is the case for actigraphy on busdriversduring travelling). In a previous work (1) this situation waspresent.In this work, attenuation of the vehicle component was obtained by filtering actograms by Singular Value Decomposition. Further, we developeda method to automatically establish the intensity of kynetic activitydeveloped for each driver, specially during the non-driving period,to obtain the ?effective? resting period during the non-driving stages.We performed a retrospective study on 20 actograms recorded (1) frombus-drivers during 10 long distance travels. Concordance between resting/ activity periods obtained by actigraphy and driving / non-drivingstages informed in their Sleep Logs, was analyzed by Bland-Altman.Effective rest durations during non-driving periods were computed andaveraged over the 20 drivers, and results compared with previous reportedby an blind expert (1) by using the Z statistic. Non significantdifferences (NS) were considered when p 0; 05.