Pneumonia is a leading cause of mortality among children under 5 years of age, accounting for more than 800,000 deaths annually.1 Oxygen (O2) is an essential therapy for hypoxaemic illnesses, including pneumonia; however, O2 is often not available on paediatric wards in resource-constrained hospitals.2,3 In the current COVID-19 pandemic, O2 demand is expected to increase dramatically in low- and middle-income countries, exacerbating this pre-existing shortage.

In resource-constrained settings, methods of delivering O2 include O2 cylinders and grid-powered O2 concentrators,4,5 both of which are limited by cost and logistical issues.2,6 Studies conducted in Uganda and Kenya reported that < 20% of paediatric wards in district hospitals have access to functional O2 delivery systems,2 with facilities experiencing power outages 7% of the time.7

Improved O2 delivery systems can lead to significant improvements in mortality from childhood pneumonia.8 We have previously detailed the design and implementation of a novel method of O2 delivery capable of implementation in remote locations with limited access to consistent electrical supplies: solar powered oxygen (SPO2).9,10 Solar powered O2 involves photovoltaic cells to collect solar energy, which is then stored in a battery bank and used to power an O2 concentrator for the production of medical grade O2. The feasibility, safety, and efficacy of SPO2 has been demonstrated through a proof-of-concept study and a randomized controlled trial, showing non-inferiority compared to cylinder O2 in terms of hospital length of stay, duration of O2 therapy, and recovery time.9,10 An evaluation of the impact of SPO2 on mortality is warranted.

The objective of this study was to compare the mortality among infants and children admitted with acute hypoxaemic respiratory illness at two resource-constrained hospitals in the Democratic Republic of the Congo (DRC) before and after installation of SPO2. We hypothesized that the introduction of a reliable source of O2 would be associated with a reduction in mortality, relative to the existing practice, in which the O2 supply was scarce and inconsistent.

Fifty patients were recruited between 1 September 2017 and 19 March 2018 (pre-SPO2). Solar-powered oxygen systems were installed in both hospitals from 5-8 October, 2018. Fifty patients were then recruited between 10 October 2018 and 1 August 2019 (post-SPO2). Table 1 shows the demographic and clinical features of the pre-SPO2 and post-SPO2 groups. Most differences between the pre-SPO2 and post-SPO2 groups were not statistically significant, with key data presented in Table 1. Table 2 shows the treatment and outcome for patients enrolled pre- and post-SPO2.

The 30-day mortality among hypoxaemic infants and children was 30/50 (60%) pre-SPO2 and 15/50 (30%) post- SPO2 (p = 0.0049). This represents a relative risk reduction of 50% (95% CI 19 – 69%) and a number needed to treat of 3.3 (95% CI 2.1 – 8.8). The survival curves pre- and post-SPO2 differed significantly (hazard ratio 0.39 [95%CI 0.20-0.74], p = 0.0043, Fig. 1).

Fig. 1.

Survival analysis of 100 infants and children hospitalized with hypoxaemia. The survival curves were significantly different pre- and post-SPO2 implementation (hazard ratio 0.39 [95% CI 0.20-0.74], p = 0.0043).

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There was a significant reduction in the number of patients experiencing interruptions to their O2 therapy from 26/50 (52%) pre-SPO2 and 1/50 (2%) post-SPO2 (p < 0.0001). More specifically, there were fewer interruptions due to fuel shortages (12/50 [24%] to 0/50 [0%], p = 0.00023) and decreased need to share O2 therapy among multiple patients (14/50 [28%] to 1/50 [2%], p = 0.00039). The duration of O2 therapy and the total volume of O2 administered increased significantly from pre-SPO2 to post-SPO2 (Table 2)

Because of the quasi-experimental design, several potential confounding factors were identified to be different in the pre-SPO2 and post-SPO2 periods including site, markers of disease severity (presence of cough, tachycardia, deep breathing), primary diagnosis (malaria versus pneumonia, sepsis and other conditions), and co-treatments (intravenous glucose, third-generation cephalosporin, ampicillin, metronidazole, and antipyretics) (Table 2). We performed a stratified analysis, examining the difference in mortality pre- and post- SPO2 in these subgroups (Fig. 2). We found a consistent reduction in mortality across multiple subgroups, suggesting that there was no confounding that would have affected the observed mortality difference pre- and post-SPO2.

Fig. 2.

Stratified analysis of mortality differences amongst 100 infants and children hospitalized with hypoxaemia pre- and post-SP02 installation. Across all strata, there was a decrease in mortality in post-SPO2 compared to pre-SPO2. * - significantly different (p < 0.05); ** - significantly different (p < 0.01).

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We next constructed multivariable logistic regression models to adjust for potential effects of co-variates (Supplemental e-Table 1). Model 1 adjusted for disease severity (RISC, coded as a continuous variable) and diagnosis (categorical variable with four levels, pneumonia, sepsis, malaria, and other), and showed that the association between lower mortality post-SPO2 remained statistically significant (adjusted odds ratio 0.31 [95%CI 0.12-0.77], p = 0.013). Model 2 adjusted for potential factors affecting mortality based on statistical considerations. Cough and malaria were both statistically significantly associated with reduced mortality and were more frequent post-SPO2. In addition, although not statistically significant, treatment with cefotaxime/ceftriaxone and intravenous glucose were associated with reduced mortality and were more frequent post-SPO2. Model 2, adjusting for cough, malaria, cefotaxime/ceftriaxone, and intravenous glucose treatment, showed that the association between lower mortality post-SPO2 remained statistically significant (adjusted odds ratio 0.30 [95%CI 0.095-0.89], p = 0.033). In summary, the post-SPO2 period was consistently and robustly associated with decreased mortality in statistical models adjusting for potential factors associated with mortality that were different pre- and post-SPO2 (Supplemental e-Table 2).

This study found that implementation of SPO2 systems was associated with a 50% decrease in 30-day mortality in children with hypoxaemic respiratory illness. Installation of SPO2 systems was associated with a reduced frequency of interruptions to O2 therapy due to fuel shortages or need to share systems among multiple patients, suggesting an improvement in the quality of care being delivered.

Oxygen availability remains a challenge in many resource-constrain settings around the world. In a survey conducted in Kenya, approximately 20% of rural healthcare facilities lacked O2 equipment. Of those with equipment, a third of their patients faced interruptions lasting a median of 11 minutes, with less than 20% having access to backup O2 cylinders.7 In Uganda, only 18% of paediatric wards had access to functional O2 delivery systems.2 Similar shortages have been reported in other resource-constrained settings across Africa.5,23 Similarly, in the current study, prior to SPO2 installation, 52% of patients experienced interruptions to their O2 therapy, half of which were due to fuel shortages leading to concentrator failure. After installing SPO2, only a single patient (2%) experienced an interruption to their O2 therapy, in their case due to multiple paediatric patients requiring the O2 concentrator simultaneously. Among survivors, the duration of O2 therapy and the total volume of O2 delivered were statistically significantly greater after SPO2 installation (Table 2), reflecting fewer interruptions and greater O2 availability. Overall, these findings suggest that the lack of available O2 equipment together with frequent power interruptions contribute to the elevated mortality associated with hypoxaemic respiratory illnesses.

While hypoxaemia is known to be associated with an increased risk of mortality in patients with acute respiratory illnesses, the mortality rate seen in our study before the implementation of SPO2 (60%) was higher than many past reports.24 This may reflect the remote, rural, and severely resource-constrained hospitals selected for this study (e.g., lack of reliable access to O2 as well as ventilators). Danger signs (i.e., not able to drink, persistent vomiting, convulsions, lethargy, stridor at rest, or severe malnutrition)25 were common in our cohort and were associated with subsequent mortality (Supplemental e-Table 1), consistent with previous studies. Of note, the frequency of danger signs and the RISC scores did not differ between the pre- and post-SPO2 periods, suggesting that the severity of presenting illness was comparable pre- and post-SPO2.

There were a number of differences, besides mortality, in patients enrolled in the post-SPO2 period, relative to the pre-SPO2 period: higher proportion of patients from the CHU Graben; higher frequency of cough and deep breathing; lower frequency of tachycardia; and higher proportion diagnosed with malaria (Table 1). Of these factors, only the presence of cough and a diagnosis of malaria were associated with decreased 30-day mortality (Supplemental e-Table 1). In a multivariable logistic regression model including these variables (Model 2, Supplemental e-Table 2), the association between SPO2 and decreased mortality remained statistically significant, suggesting that the higher proportion of children with cough and malaria post-SPO2 did not explain the observed mortality reduction.

This study builds on our group's previous work evaluating SPO2 in resource-constrained settings. Previously, we have demonstrated proof-of-concept,10 non-inferiority relative to cylinder O2,9 and cost-effectiveness26 of SPO2. The current study provides quasi-experimental evidence of mortality reduction associated with SPO2. Additional experimental evidence from cluster-randomized controlled trials will be needed to conclusively show that SPO2 reduces mortality. Currently, we are conducting a stepped-wedge cluster-randomized controlled trial of SPO2 at 20 sites across Uganda.27

The median length of hospital stay was 6 days (interquartile range [IQR] 5-7) pre-SPO2 and 8 days (IQR 5-10) post-SPO2, a difference that approached statistical significance (p = 0.054). The possible prolongation of duration of admission may be due to delay in discharge with improved recognition of clinically apparent hypoxaemia that resulted from increased use of pulse oximeters with our study. Of note, one previous randomized controlled trial demonstrated that SPO2 was not associated with prolonged length of stay, relative to cylinder O2.9

Our study has several limitations. Quasi-experimental before-after designs are subject to the confounding effects of time and lack a distinct control group.18 Indeed, imbalance in co-treatments (e.g., intravenous glucose) pre- and post-SPO2 were directly attributable to improvements in patient care that arose as a result of our study. Potential confounding variables were examined through stratified analyses (Fig. 2) and multivariable modelling (Supplemental e-Table 2). Nonetheless, further investigation is required to conclusively show mortality benefit of SPO2. The limited samples size (50 patients in each group) restricted the number of co-variates that could be included in multivariable models. This sample size is small relative to the burden of disease globally and relative to the patient volumes treated at the participating facilities. A larger study would be desirable to comprehensively adjust for co-variates. Moreover, replication of these findings in other resource-constrained settings would be needed to demonstrate the generalizability of these findings.

SPO2 installation was associated with a marked reduction in mortality among children hospitalized with hypoxaemia in two resource-constrained hospitals. SPO2 is an innovative and simple approach to providing therapeutic O2 to resource-constrained settings. Its ease-of-use, cost-effectiveness, and efficacy in decreasing childhood mortality make it an accessible and effective solution to the high burden of childhood pneumonia. O2 requirements have spiked globally during the ongoing COVID-19 pandemic, and SPO2 can provide a useful countermeasure in resource-constrained settings.

The authors have no conflicts of interest to declare.

This study was funded by The Rotary Foundation (Rotary Global Grant GG1755779). The funder had no role in the study design, analysis and interpretation or results, or decision to publish the manuscript.

None.