Bronchiolitis is a viral infection of the lower respiratory tract that mainly affects infants during their first 12 months of life, limited to the first two episodes [1] . Respiratory syncytial virus (RSV) is the main pathogen, responsible for approximately 60% to 80% of cases [2] . Recognized as a major public health problem due to its morbidity and increasing incidence each year, bronchiolitis poses challenges for management in both developing and industrialized countries [3] . Globally, it is the leading cause of hospitalization for acute respiratory distress in infants, with nearly 3.2 million admissions per year and approximately 59,600 deaths [4] [5] . In France, it affects 30% of infants each winter, with a mortality rate of 1% [6] . Bronchiolitis is associated with one in 15 deaths in infants under 12 months of age, mainly in developing countries [4] . In Sub-Saharan Africa, it is also a common condition. Its hospital prevalence is 9.4% in Cameroon and 5.33% in Madagascar [7] [8] . In Congo, bronchiolitis is the leading acute lower respiratory infection (ALRI), with a hospital prevalence of 56.5% [9] .

The treatment of severe bronchiolitis requires hospitalization in a pediatric intensive care unit with respiratory support, including conventional oxygen therapy or continuous positive airway pressure (CPAP).

Conventional CPAP is a non-invasive ventilation technique that is rapidly developing in the pediatric field [9] . Several studies, including that of Milési, have shown its effectiveness in rapidly reducing respiratory effort in infants with severe bronchiolitis [10] .

Countries with limited resources in Asia and Sub-Saharan Africa that do not have equipment for conventional CPAP often resort to the use of homemade CPAP in the treatment of infants with severe bronchiolitis [11] . In Brazzaville, few studies have documented the therapeutic modalities for this condition. The objective of this study was to compare the efficacy of homemade CPAP with that of conventional oxygen therapy using a high-flow mask in the management of severe bronchiolitis in infants in Brazzaville.

A single-blind, parallel-group, randomized controlled trial was conducted from October 1, 2023, to November 1, 2024, in the pediatric intensive care units (PICUs) of three level 3 hospitals in the health department of the city of Brazzaville: the Brazzaville University Hospital Center (CHU-B), the Blanche Gomez Mother and Child Specialized Hospital (HSMEBG), and the Djiri General Hospital (HGD). This trial involved two groups of infants who were hospitalized for severe acute bronchiolitis (SAB): the first (group 1) consisted of all infants who received homemade CPAP respiratory support, and the second (group 2) consisted of those who received conventional oxygen therapy with a high-flow mask. The study included infants aged between one and 12 months who were hospitalized in the above-mentioned departments for severe bronchiolitis, with the consent of their parents. The definition of severe bronchiolitis used for this study was that updated by the Haute Autorité de Santé (HAS) in France [12] . The centers were chosen non-probabilistically, as they are the only centers with a pediatric intensive care unit. Infants were recruited consecutively and exhaustively as they were admitted. The number of subjects required for the trial was calculated based on the primary endpoint, which is the length of hospital stay; Kelsey’s formula: $N=\frac{{2{\delta }^2(Z\alpha /2+Z1-\beta )}^2}{{\Delta }^2}$ was used to calculate the sample size. According to the study conducted by INOURI [13] , the average length of hospital stay was 7 days for the CPAP group with a standard deviation of 2.26 and 10 days for the control group with a standard deviation of 3.19. We therefore have a standard deviation of 3 in both groups (standard deviation = δ = 3 =˃ δ² = 9 days, 1 − β = 80%, i.e. β: 20%, Z2 β = 0.842). Where N1 is the number of subjects required in group 1, N2 is the number of subjects required in group 2, N = N1 = N2, and α is the risk of being wrong in claiming that the treatment works. Zα/2: α risk value of 5%, in a two-tailed hypothesis, Zα = 1.96, β: risk of being wrong in stating that the treatment does not work. Z_β = β risk value of 20%, Δ: the expected difference between the two means to be compared, Δ = m1 − m2, δ: common variance. N₁ = N₂ = $2{\left(3\right)}^2\frac{\left(1.96+0.842\right)}{3^2}$ = $\frac{18\times 9}{9}$ = 19. The minimum sample size calculated was 19 subjects in each group, but to minimize bias, we recruited 60 infants for each group. The homemade CPAP is a non-industrial device assembled at the patient’s bedside using readily available components: an oxygen mask, a plastic mineral water bottle, adhesive tape, an oxygen distribution circuit, an infusion pump, and an oxygen pressure regulator ( Iconography 1 and Iconography 2 ). This device is designed to provide continuous positive pressure (5 to 10 liters) in the airways of patients with respiratory distress in order to recruit the alveoli and promote hematosis. To assemble this device, one end of the oxygen mask is cut off and becomes the expiratory tube, which is immersed in the water bottle at a depth in centimeters equivalent to the continuous positive pressure. The regular presence of bubbles in the bottle is a sign that positive pressure is being created, dilating the alveoli. Another tube placed in the same bottle is used to escape gases.

The clinical evaluation of treatment efficacy was performed using a pre-established and pre-tested questionnaire. This questionnaire was designed based on the modified Wang [14] and modified Wood [15] scores, which are standardized scores used to assess the severity of bronchiolitis and asthma attacks, respectively. This questionnaire consisted of five items, including respiratory rate (RR), heart rate (HR), pulse oxygen saturation (SaO₂), signs of struggle, and wheezing. Each item was scored from 0 to 3 ( Table 1 ). This score was assessed at 15 minutes, 30 minutes, and 1 hour after treatment, then daily for 3 days. The percentage reduction in signs of severity was assessed using the following formula: [(Score on admission – score after treatment)/Score on admission] × 100. The clinical progression of study participants was classified as follows: good clinical progression (75% < score ≤ 100%), moderate clinical progression (50% < score ≤ 75%), and poor clinical progression (score ≤ 50%).

HR: Heart rate; RR: Respiratory rate.

Infant recruitment procedure is shown in Figure 1 .

This multicenter study was a randomized, parallel-group, single-blind clinical trial. Its aim was to contribute to improving the management of severe bronchiolitis in infants hospitalized in pediatric wards in Brazzaville. The choice of study type focused on innovation in the therapeutic approach, as it was based on a rigorous method that minimizes bias and ensures the comparability of results at a lower cost. However, the study encountered certain difficulties, including the practical variability of homemade CPAP devices and the limited technical capabilities that prevented certain biological tests, such as blood gas and blood ionogram tests, from being performed. The evolution of certain parameters could not be evaluated during treatment.

In Brazzaville, severe bronchiolitis is most common in infants under 6 months of age, as evidenced by the median age of infants in this study, which is 3 months [IQR: 2 - 5.75]. The work of Tsifiregna et al. in Madagascar found that 66.7% of bronchiolitis cases occurred in infants under 6 months of age [8] . The young age of the infant is recognized as a factor in the severity of bronchiolitis [16] . Severe bronchiolitis affects boys (62.5%) more than girls, with a sex ratio of 1.8 in our population. This result is comparable to that reported by Ouologuem in Bamako [17] . The predominance of males in bronchiolitis is thought to be related to the narrowness of the bronchi in young boys [18] .

CPAP has become an increasingly popular treatment for bronchiolitis in recent years due to its advantages over conventional oxygen therapy. Homemade CPAP is an equally effective alternative for the treatment of severe bronchiolitis in low-income countries, as shown by the results of this study. Homemade CPAP improved the signs of respiratory distress in infants more quickly than conventional oxygen therapy, with a statistically significant difference (p < 0.001). These results are similar to those of Essouri et al.’s study, which reported a significant reduction in respiratory effort in infants receiving CPAP within a median time of 48 hours [19] . According to Ganu et al. in India, CPAP significantly reduces the duration of respiratory distress and improves respiratory efficiency compared to conventional oxygen therapy [20] . These results are attributed to the airway-stabilizing effect and reduction in alveolar collapse induced by CPAP.

The homemade CPAP device led to a reduction in respiratory rate from the first day of treatment. Our results are similar to those of studies by Kamal et al. and Dayan et al. [21] [22] , who observed a significant decrease in respiratory rate between the two groups in favor of CPAP. However, Mélési et al. [10] and Thia et al. [23] did not find a significant change in respiratory rate. Differences in treatment protocols, characteristics of the study populations, or measurement criteria used could explain this disparity. Improvement in pulse oxygen saturation (SpO₂) was greater in the homemade CPAP group than in the conventional oxygen therapy group from the first day of treatment (p = 0.000). These results are consistent with those of Dayan et al. [22] and Karmal et al. [21] , who also observed a significant difference. The improvement in oxygenation is due to the opening of the airways, under the effect of the positive pressure support provided by the homemade CPAP, which improves the ventilation-perfusion mismatch, a key element in the pathophysiology of bronchiolitis. In addition, the reduction in respiratory effort allows for good oxygenation. Oxygen requirements are therefore improved more quickly (from the first hour) in the CPAP group.

In this study, we noted that the risk of bacterial superinfection was lower in the homemade CPAP group than in the conventional oxygen therapy group (2.3% vs. 11.6%), although the difference was not statistically significant. Inouri’s 2021 study reported a statistically significant difference in the occurrence of superinfection between the two groups [13] . The short length of hospital stay for infants in the CPAP group would certainly minimize the risk of bacterial superinfection. The low overall mortality rate of bronchiolitis (1.6%) in this study is similar to that reported by Inouri [13] and Che et al. [24] . According to these authors, deaths occurred mainly in the conventional oxygen therapy group, as in our case. The two deaths in this study occurred in the context of acute respiratory distress syndrome (ARDS). Hammer, in a study on RSV-related deaths, also reported only one death among 37 infants included in the study.

Homemade CPAP is an effective therapeutic method that reduces the length of hospital stay for infants with severe bronchiolitis compared to oxygen (3.2 ± 1.1 days vs. 4.3 ± 1.7 days) (p = 0.000); this finding is identical to that reported by Pierre et al. [25] . Early introduction of non-invasive ventilation, such as homemade CPAP, reduces the length of hospital stays and the occurrence of associated complications.

Bronchiolitis is a public health issue. In Brazzaville, it mainly affects male infants under 6 months of age from low socioeconomic backgrounds. Homemade CPAP seems to be a promising alternative for treating severe bronchiolitis in our resource-limited setting. It allows for rapid improvement in the respiratory status of infants and normalization of pulse oxygen saturation. In addition, it reduces the length of hospitalization, the occurrence of complications, and the number of deaths. Further, larger-scale studies appear to be necessary to refine treatment protocols and ensure the safety of its long-term use.