Evaluating the effects of air cushions on body pressure distribution and thermal insulation in evacuation shelters: A randomized controlled crossover study

In large-scale disasters such as the anticipated Nankai Trough Earthquake, millions of evacuees are expected to remain in shelters, often sleeping on cold, hard floors in classrooms and gymnasiums, contributing to musculoskeletal pain and sleep disruption. While cardboard beds have been employed since the Great East Japan Earthquake due to their rapid mass-production capability, municipalities are not required to stockpile them, and many were unable to provide sufficient quantities during the Kumamoto Earthquake. Furthermore, the large size and weight of these beds complicate timely delivery, and their use alone provides only limited body pressure distribution. Consequently, there is concern that large-scale disasters will result in a severe shortage of appropriate bedding. This study aimed to determine whether air cushions can provide sufficient body pressure distribution and thermal insulation to serve as practical floor mats in evacuation shelters. Twenty healthy adults were enrolled in this randomized controlled crossover trial. Participants were instructed to lie on an air cushion, a urethane pad, and a plastic sheet, during which body pressure distribution was evaluated. Subjective perceptions of firmness and comfort were assessed using a numeric rating scale, and thermal insulation properties were evaluated by measuring surface temperature changes when each material was placed over a cooling gel pack. Compared with plastic sheets, the air cushion reduced mean body pressure by over 20% and increased contact area by more than 30%, with improvements exceeding those observed for urethane pads. Participants rated air cushions as significantly less firm and more comfortable than urethane pads. The air cushion also demonstrated thermal insulation comparable to urethane pads. These findings suggest that air cushions could serve as practical emergency floor mats in evacuation shelters, complementing cardboard beds and potentially reducing musculoskeletal strain and sleep disturbances in disaster settings.