Hypoxemia is a severe condition associated with high rates of mortality, particularly in low- and middle-income countries (LMICs) with poor access to oxygen therapy. Despite its clinical significance, there have been few studies to describe the burden of hypoxemia. Thus, the primary objective of this study is to systematically describe the prevalence of hypoxemia among pediatric and adult patients in low- and middle-income countries. Standard systematic review methods will be used. Bibliographic databases (MEDLINE, EMBASE, CINAHL) will be searched from 1998 onwards. The search strategy aims to identify studies that have measured peripheral blood oxygen saturation (SpO2) in children and adults presenting to health facilities in LMICs. Studies will be included if oxygen saturation measurements by pulse oximetry were measured. No studies will be excluded based on study design though patients recruited from intensive care units and post-operative care will be excluded. The primary outcome is the prevalence of hypoxemia on presentation to the healthcare facility. We define hypoxemia on the basis of SpO2 measurements, and use a threshold of SpO2 less than 90% at sea level though allow for a lower threshold for studies conducted at higher altitude and where justified. Standardized tools will be used to extract data on number of patients with SpO2 measurements, number of patients with hypoxemia, patient population characteristics, and study characteristics. Quality of the included studies will be assessed using the “Checklist for Prevalence Studies” developed by the Joanna Briggs Institute. If there are enough studies to do so, we will conduct meta-analysis using a random effects model to estimate prevalence of hypoxemia and conduct subgroup analyses by age and disease groups. Hypoxemia is a critical condition and understanding the burden of hypoxemia may support decision-making in LMICs to deploy pulse oximeters and oxygen treatments more efficiently to address diseases and patient populations with the highest burden. Previous studies on hypoxemia prevalence have focused too narrowly on a few diseases or specific patient populations (e.g., pneumonia in children under five) whereas any effort to improve access to oxygen requires understanding of the potential demand for oxygen for all diseases and population groups. Governments, UN agencies, donors, and NGOs are investing strongly to improve oxygen systems in LMICs. Effective oxygen system planning requires estimation of oxygen need, informed by robust data on hypoxemia prevalence and admission patterns at all the levels of the health system. This study aims to fill that gap by providing comprehensive estimates of hypoxemia prevalence. PROSPERO CRD42019136622.

中文翻译：

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低收入和中等收入国家医疗机构就诊的儿科和成人患者的低氧血症患病率：系统评价和荟萃分析方案

低氧血症是一种与高死亡率相关的严重疾病，特别是在氧疗难以获得的低收入和中等收入国家 (LMIC)。尽管具有临床意义，但很少有研究描述低氧血症的负担。因此，本研究的主要目的是系统地描述低收入和中等收入国家儿科和成人患者的低氧血症患病率。将使用标准的系统评价方法。从 1998 年起将检索书目数据库（MEDLINE、EMBASE、CINAHL）。搜索策略旨在确定在 LMICs 医疗机构就诊的儿童和成人外周血氧饱和度 (SpO2) 测量的研究。如果通过脉搏血氧仪测量氧饱和度，则将纳入研究。尽管从重症监护室招募的患者和术后护理将被排除在外，但不会根据研究设计排除任何研究。主要结果是就诊时低氧血症的发生率。我们根据 SpO2 测量值定义低氧血症，并在海平面使用低于 90% 的 SpO2 阈值，但允许在较高海拔和合理情况下进行的研究使用较低阈值。标准化工具将用于提取有关 SpO2 测量患者数量、低氧血症患者数量、患者群体特征和研究特征的数据。纳入研究的质量将使用 Joanna Briggs 研究所制定的“患病率研究清单”进行评估。如果有足够的研究可以做到这一点，我们将使用随机效应模型进行荟萃分析，以估计低氧血症的患病率，并按年龄和疾病组进行亚组分析。低氧血症是一种危急情况，了解低氧血症的负担可能会支持 LMIC 的决策，以更有效地部署脉搏血氧仪和氧气治疗，以解决负担最高的疾病和患者群体。以前关于低氧血症患病率的研究过于狭隘地关注少数疾病或特定患者群体（例如，5 岁以下儿童的肺炎），而任何改善氧气获取的努力都需要了解所有疾病和人群对氧气的潜在需求。政府、联合国机构、捐助者和非政府组织正在大力投资以改善中低收入国家的氧气系统。有效的氧气系统规划需要根据卫生系统各级低氧血症患病率和入院模式的可靠数据来估计氧气需求。本研究旨在通过提供对低氧血症患病率的全面估计来填补这一空白。PROSPERO CRD42019136622。