Background: The AIRE project has implemented routine Pulse Oximeter (PO) use in Integrated Management of Childhood Illness (IMCI) consultations to improve the diagnosis and care management of severe illnesses in primary health centre (PHC) in Burkina Faso, Guinea, Mali and Niger. We analysed care management of severe cases according to hypoxemia, and the determinants of their Day-14 mortality. Methods: All children under-5 attending IMCI consultations using PO and classified as severe cases (severe IMCI cases or with severe hypoxemia: SpO2<90%) were enrolled at 16 research PHCs (four/country) in a 14-Day prospective cohort with parental consent. Care management according to hypoxemia severity and determinants of Day-14 mortality were analysed. Results: From June 2021 to June 2022, 1,998 severe cases, including 212 (10.6%) aged <2 months were enrolled. Severe hypoxemia was common (7.1%), affecting both respiratory cases (9.9%) and non-respiratory cases (3.7%); 10.5% had moderate hypoxemia (90%≤SpO2≤93%). Overall, 463 (23.2%) have been hospitalised. At Day-14, 95 (4.8%) have died, and 27 (1.4%) were lost-to-follow-up. The proportions of referral decision, hospitalisation and oxygen therapy were significantly higher for severe hypoxemic cases (83.8%, 82.3%, 34.5%, respectively) than for those with moderate hypoxemia (32.7%, 26.5%, 7.1%, respectively) or without hypoxemia (26.3%, 17.5%, 1.4%, respectively). Similarly, Day-14 mortality rates were 26.1%, 7.5% and 2.3% respectively (p<0.001). Death occurred within a median delay of one day for severe hypoxemia. In an adjusted mixed-effect Cox model, age <2 months, severe and moderate hypoxemia, severe malaria, and place of case management elsewhere than at PHC independently increased mortality at Day-14. Conclusion: Both severe and moderate hypoxemia were frequent among outpatient critically ill children diagnosed using PO, and associated with a high mortality. Although, the diagnosis of hypoxemia prompted their care management, hospital referral and access to oxygen remain sub-optimal and crucial levers for reducing under-5 mortality in West Africa.
