Acute lower respiratory infections (ALRI) are the leading cause of death in children under 5 years old. There is a high prevalence of pediatric ALRI-related hypoxemia in low- and middle-income countries (LMICs). Building on past successes, this proposal aims to advance the use of pulse oximetry in LMICs. In Malawi a SpO2 (peripheral oxygen saturation) of 90-92% was associated with child ALRI mortality which is consistent with a retrospective study from the United States that reported SpO2 may over-estimate arterial oxygen saturation (SaO2) by 4.3% in Black children. Pulse oximeters are not universally available in outpatient settings in LMICs due to a lack of health system financing. Government stakeholders often must prioritize low, or perceived, low cost high output interventions. However, the cost of pulse oximetry implementation in these settings remains unknown. For outpatient pulse oximeters to reduce child ALRI mortality, they must accurately and reliably measure SpO2 and be financially and time cost effective. The aims of this mixed methods study are to 1) examine the accuracy of SpO2 in children with dark and fair skin tones and 2) compare the costs of ambulatory reflectance versus transmissive pulse oximetry implementation for outpatient child ALRI care in South Africa. These aims address the NHLBI's mission to lead the world in advancing translational research that bridges the gap between clinical research to practice and population to health outcome. Interventions to improve early identification of hypoxemic children and provision of appropriate care are critical to reduce child ALRI mortality. This proposal leverages the unexplored roles of cost analysis and compares objective findings with clinician perceptions of time-costs in pulse oximetry use and generates critical racial health disparity-related data to inform future studies aimed at improving equitable care and treatment by refining SpO2 interpretation. Dr. Hooli is a pediatric emergency medicine physician with years of clinical experience in LMICs and the United States. These experiences framed the aims and shaped her career focus on patient-oriented research. The educational plan includes formal, tutorial, and practical experiences in prospective study design and analysis, cost analysis, and implementation science. She is mentored by internationally recognized scientists with expertise in these fields and child pneumonia, global health, and pulse oximetry. Execution of these aims coupled with the educational and mentorship plan outlined in the proposal will prepare Dr. Hooli to become an independent investigator.