Hypoxaemia and mortality in children with lower respiratory infection in low-income and middle-income countries: systematic review and meta-analysis.

Abstract

Hypoxaemic lower respiratory infections (LRIs) are a leading cause of childhood mortality, with the highest burden in low-income and middle-income countries (LMICs). Hypoxaemia-low peripheral capillary oxyhaemoglobin saturation (SpO₂)-is a marker of severity, and WHO recommends hospitalisation and oxygen administration for patients with SpO₂ <90%. We aimed to update estimates from a 2015 systematic review and meta-analysis examining the association between hypoxaemia and mortality among children with LRIs in LMICs by incorporating studies published over the subsequent decade and evaluating mortality risk across multiple SpO₂ thresholds. We conducted a systematic review with meta-analysis by searching PubMed, Embase, LILACS, Global Index Medicus, Web of Science, and Scopus for peer-reviewed studies published between Jan 1, 2015, and June 18, 2025, with combined terms related to pneumonia, children, mortality, and LMICs. We also included selected earlier studies through citation checking. Eligible studies reported associations between hypoxaemia and mortality in children younger than 5 years with LRIs in LMICs. We excluded case reports and case series with fewer than five deaths, studies focused exclusively on the neonatal period, and those limited to children with specific comorbidities or to postoperative patients, for consistency with the original review. Two reviewers independently screened studies, extracted data, and assessed quality. Eligible studies were combined with those from the original review and analysed using random-effects models to estimate odds ratios (ORs) by hypoxaemia threshold subgroup. The protocol was registered on PROSPERO (CRD42023433946). We identified 7734 records; 26 new studies met inclusion criteria and were combined with 18 from the original review. The 44 studies were published between 1993 and 2024 and were primarily from Africa (25 [57%] of 44) or Asia (19 [43%]); some studies spanned multiple locations. Data from 33 studies including 155 633 participants were included in the primary meta-analysis. Hypoxaemia of any threshold was associated with higher odds of LRI mortality (OR 4·36 [95% CI 3·52-5·39]) compared with no hypoxaemia. For SpO₂ <90% versus 90-100%, OR for death was 4·75 (95% CI 3·42-6·58). For SpO₂ 90-94% versus 95-100%, mortality risk was more than twice as high (OR 2·27 [95% CI 1·22-4·25]). Heterogeneity was substantial (I² 64-85% across analyses), and eight (24%) of 33 studies in the primary meta-analysis had a high overall risk of bias; however, a sensitivity analysis restricted to studies with low or moderate risk of bias yielded similar results. SpO₂ <90% strongly predicts mortality in children with LRIs in LMICs. Children with SpO₂ 90-94% also have elevated risk, suggesting that paediatric LRI and pneumonia treatment algorithms should consider management at this hypoxaemia threshold. None.