Biomechanical-based hazard analysis of inclined sleepers

Abstract

It is well known that infants should be placed to sleep supine on a firm horizontal surface. Despite these long-standing safe-sleep guidelines, the juvenile products industry marketed inclined sleepers for over a decade. In 2019, the industry recalled several million of the devices due to numerous reports of infant deaths being associated with the products. The hazards of inclined sleepers can be understood and evaluated through an analysis of the physical structure combined with a biomechanical analysis of the infants placed into the devices. Several hazards unique to inclined sleepers, that are not present in flat cribs, are identified in this study. Key hazards include infants rolling supine-to-prone, the feet of prone infants losing contact with the sleeping surface, infant faces in contact with non-breathable fabric, infant arms trapped by steep sidewalls, and unsafe restraint systems that are easily misused by caregivers. This paper presents a first-principles biomechanical-based hazard analysis integrated with a fault tree analysis. The biomechanical analyses incorporating root-cause reasoning for the hazard mechanisms may serve to guide the design and improve the safety of future products. Furthermore, an important conclusion is that adhering to industry standards does not guarantee hazard mitigation for the diverse forms of products within any given category.