Review
The prevalence of hypoxaemia among ill children in developing countries: a systematic review

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Summary

Hypoxaemia is a common complication of childhood infections, particularly acute lower respiratory tract infections. In pneumonia—a disease that disproportionately impacts developing countries, and accounts for more than two million deaths of children worldwide—hypoxaemia is a recognised risk factor for death, and correlates with disease severity. Hypoxaemia also occurs in severe sepsis, meningitis, common neonatal problems, and other conditions that impair ventilation and gas exchange or increase oxygen demands. Despite this, hypoxaemia has been overlooked in worldwide strategies for pneumonia control and reducing child mortality. Hypoxaemia is also often overlooked in developing countries, mainly due to the low accuracy of clinical predictors and the limited availability of pulse oximetry for more accurate detection and oxygen for treatment. In this Review of published and unpublished studies of acute lower respiratory tract infection, the median prevalence of hypoxaemia in WHO-defined pneumonia requiring hospitalisation (severe and very severe classifications) was 13%, but prevalence varied widely. This corresponds to at least 1·5 to 2·7 million annual cases of hypoxaemic pneumonia presenting to health-care facilities. Many more people do not access health care. With mounting evidence of the impact that improved oxygen systems have on mortality due to acute respiratory infection in limited-resource health-care facilities, there is a need for increased awareness of the burden of hypoxaemia in childhood illness.

Introduction

The fourth Millennium Development Goal has concentrated efforts on addressing priority areas for improving worldwide child survival, with the aim of reducing national child mortality rates by two-thirds between 1990 and 2015.1 The 30th anniversary of the Alma Ata conference2 rightly emphasised that advances in primary health-care interventions are needed if the fourth Millennium Development Goal is to be achieved. As part of the primary-care approach, children with severe illness require access to good quality basic first-referral-level care. Pneumonia is the leading cause of death in children younger than 5 years, being responsible for at least 19% of the annual 9·7 million deaths in this age-group.3 Advances in the case-management of major causes of child death, such as pneumonia and neonatal conditions, should be a priority in improving child survival.2, 4

In pneumonia, hypoxaemia is a predictor of severe disease and has been shown to be a risk factor for death.5, 6 There is now evidence that ensuring ample supplies of oxygen and promoting a routine and systematic approach of screening for hypoxaemia using pulse oximetry is associated with improved quality of care and reduced mortality, and that the technology required to do so is sustainable and affordable in district hospitals in developing countries.5, 7, 8, 9, 10, 11 Despite such evidence, oxygen remains inaccessible for a substantial proportion of severely ill children admitted to hospitals in developing countries. The inaccessibility of oxygen is particularly true for those admitted to district-level hospitals, where even if some facility for delivering oxygen is available, supplies are often unreliable, equipment is poorly maintained, or there is a lack of staff training or guidelines.12, 13, 14 Moreover, oxygen therapy in developing countries continues to be a low priority on the child-health agenda. Oxygen was not mentioned, for example, in the recent publication by WHO and UNICEF on efforts to control pneumonia.3

Studies have explored the possibility of managing children with WHO-defined severe pneumonia and no danger signs at home, thereby directing the limited facility-based health-care resources to children most in need of them.15 For home management to be safe and ethical, it is essential that only children without hypoxaemia are managed outside health-care facilities. Children with hypoxaemic pneumonia need to be identified (which is difficult using only clinical signs), admitted, and given supplemental oxygen and close monitoring. This necessitates a heightened awareness of the prevalence and risk of hypoxaemia among children presenting to health-care facilities, and robust mechanisms to detect it.

Increased awareness of the important role of oxygen in improving child survival requires a better understanding of the global burden of hypoxaemia in children. In this systematic review we bring together the current knowledge from published and unpublished data on the prevalence of hypoxaemia amongst acutely ill children and neonates in developing countries.

Section snippets

Search strategy

Systematic literature searches were conducted in December 2006 (by MA), and updated in November 2008 (by RS). The electronic databases used were: Medline (1950 to July 2008), EmBase (1980 to 2008 week 26), and Global Health (1973 to July 2008). The search was conducted using various combinations of the following terms: “anoxia/hypoxaemia/hypoxemia”, “pneumonia”, “oximetry/oxymetry”, “arterial oxygen saturation”, “developing countries”, and “children”, with limits for studies of children younger

Results

Figure 1 shows the number of studies that were included and the reasons for exclusion. The search of the published literature yielded 27 papers comprising 26 cohort analyses and one systematic review, which was excluded. Another 14 studies did not fit all of the selection or quality criteria and were excluded. Four of these used a high definition of hypoxaemia21, 22, 23, 24 and another five studies of hypoxaemia had a sample size of less than 100 children.25, 26, 27, 28, 29 For one study, there

The global burden of hypoxaemia

This Review highlights the substantial burden of hypoxemia in childhood infections in developing countries, and the differences in data reported between regions and studies. In terms of the magnitude of the problem, in the developing world each year there are an estimated 150 million episodes of pneumonia, 11–20 million of which require hospitalisation.48, 49 If the median prevalence in studies of children with severe or very severe pneumonia is representative of the worldwide burden of

Conclusions

Hypoxaemia is a very common and treatable complication of childhood respiratory and non-respiratory infections in developing countries. Investment in pulse oximetry for the diagnosis of hypoxaemia will allow more precise classification of disease severity than that currently possible using clinical signs. Other conditions, particularly in the neonatal period, make up an additional substantial burden of hypoxaemia in developing countries. Global awareness of this aspect of the management of sick

Search strategy and selection criteria

These are described in detail in the Methods section.

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