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Reduction in the exposure to being out-of-position among car occupants who used a sleeping device
  1. Francisco J Lopez-Valdes1,2,
  2. Marta Fernandez-Bolanos Martin3,4,
  3. Ainhoa Alvarez Ruiz-Larrinaga3,
  4. Maria Segui-Gomez1,2
  1. 1University of Virginia, Center for Applied Biomechanics, Charlottesville, Virginia, USA
  2. 2European Center for Injury Prevention (ECIP), School of Medicine, Universidad de Navarra, Pamplona, Spain
  3. 3Sleep Unit, Hospital Universitario Txagorritxu, Vitoria, Spain
  4. 4Ciber de Enfermedades Respiratorias (CibeRes), Instituto de la Salud Carlos III, Madrid, Spain
  1. Correspondence to Francisco J Lopez-Valdes, Center for Applied Biomechanics, University of Virginia, 4040 Lewis and Clark Drive, Charlottesville, VA 22911, USA; fjl2j{at}


Background This study assesses the impact on safety of a system designed to enhance sleep in car passengers. The system holds the head posteriorly and limits its rotation in the sagittal and frontal planes, modifying the occupant's head position. This device may have an influence on the interaction between the occupant and the vehicle restraint systems.

Methods It was a randomised, prospective, single-blind, cross-over controlled study in which 41 volunteers were exposed to using the system while riding as car passengers. Whether the device influenced the posture of the occupants and prevented them from adopting out-of-position (OOP) configurations was also analysed. Occupants were videotaped while they were using both the innovative system (cases) and their normal sleeping device (controls), if any.

Results Controls were exposed to OOP situations in 825 occasions (18.4%; 95% CI 17.3% to 19.6%), while cases were exposed in 416 occasions (9.3%; 95% CI 8.4% to 10.2%). The paper also analysed how many cases and controls were exposed at least once to a particular event and how frequent a single participant incurred in an OOP situation. In both cases, the innovative device showed a reduction in exposition. When OOP situations were grouped into severe, moderate and minor events, the innovative device produced a statistically significant reduction in the occurrence of severe and moderate events.

Conclusions A device originally designed to improve comfort and rest in car passengers has been found to reduce the exposure of the occupants to being OOP while resting in the car.

Trial registration number, NCT01062295.

  • Air bags
  • seat belts
  • out-of-position
  • traffic injuries
  • engineering
  • motorcycle
  • passenger
  • biomechanics
  • child
  • policy
  • severity
  • score
  • international
  • developing nations

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  • Funding The analysis presented in this manuscript (including review of the recordings for out-of-position counts) was funded through discretionary funding from the European Center for Injury Prevention at the Universidad de Navarra. This manuscript summarises secondary analyses of data already collected under registered trial (, NCT01062295). The original data collection and analysis focusing on the effectiveness on sleep amount and quality were partly sponsored by a grant from the Health Department of the Basque Country government (2009111063), under agreement with the researchers from the Sleep Unit of the Hospital Universitario Txagorritxu (Spain).

  • Competing interests None.

  • Ethics approval Human Ethics Committee of Hospital Universitario Txagorritxu, Vitoria, Spain.

  • Provenance and peer review Not commissioned; externally peer reviewed.