Perceived workload using separate (filtering facepiece respirator and face shield) and powered air-purifying respirator and integrated lightweight protective air-purifying respirator: protocol for an international multisite human factors randomized crossover feasibility study - Price, Amy; Lin, Ying Ling; Levin, Anna S; Tumietto, Fabio; Almeida, Rodrigo; Almeida, Ana; Ciofi-Silva, Caroline Lopes; Fontana, Luca; Oliveira, Naila; Parisi, Nicola Francesco; Mainardi, Giulia Marcelino; Cordeiro, Luciana; et al. (JMIR research protocols, 2022)