PROJECT SUMMARY Children who survive critical illness requiring prolonged mechanical ventilation are at high risk of significant and long-lasting sequelae including physical and pulmonary function impairments and impairments in health-related quality of life and the ability to return to previously normal activities. These impairments may be mitigated through targeted interventions during the pediatric intensive care unit stay or after discharge. The ability to effectively test interventions is hindered by insufficient methods to objectively quantify post-discharge physical and pulmonary impairments across representative study populations without significant attrition. Additionally, we have an incomplete understanding of the relationship between trajectory recoveries across different health domains and methods of measurement. The objective of this proposal is to validate the use of digital technologies to objectively measure physical activity and pulmonary function and evaluate the relationship between recovery trajectories of objectively measured physical and pulmonary functioning and patient-reported outcomes including health-related quality of life and activity participation in children surviving acute respiratory failure. We will compare the BioIntellisense BioButton, a discreet wearable device used in adults to monitor physical activity and the Spirobank Smart Spirometer, a remote digital spirometer, against the gold standards of wrist-worn accelerometry and laboratory spirometry, respectively. We will also collect patient-reported outcomes evaluating health-related quality of life and activity participation. This proposal will identify and validate strategies for remote follow-up of children that optimize patient participation and retention using digital technologies to expand patient representation and reduce disparities in clinical research participation. Additionally, it will inform a future R01 proposal to test an intervention aimed at recovery after pediatric acute respiratory failure by providing a more comprehensive understanding of the associations between recovery of physical and pulmonary functioning, health-related quality of life, and activity participation.