Acute bronchiolitis is the most frequent lower respiratory tract infection in infants and the leading cause of hospital admission in this age group during the epidemic season.

General supportive measures and respiratory support are the mainstay of treatment, as the evidence shows that most pharmacological interventions are not efficacious.1–4

Until a few years ago, a high number of the children with bronchiolitis that developed respiratory failure required invasive mechanical ventilation (IMV), which increased the length of stay and the risk of complications. In recent years, there has been an increase in the use of non-invasive ventilation1 (NIV), but the effects of this treatment on the use of IMV and clinical outcomes are not well understood.

The aim of this study was to analyse the evolution in the use of IMV and NIV in children with acute bronchiolitis admitted to the paediatric intensive care unit (PICU) over a period of 12 years, with the hypothesis that the increase in the use of NIV would be associated with a reduced need for IMV, shorter lengths of stay and lower mortality.

We conducted a retrospective observational study of patients admitted to the PICU between January 1, 2001 and December 31, 2012 with a diagnosis of bronchiolitis that required IMV or NIV. Patients that were only treated with high-flow oxygen therapy were not included in the study. We collected data for the following variables: age, sex, need for IMV and NIV, duration of mechanical ventilation, type of NIV: continuous positive airway pressure (CPAP) or bilevel positive airway pressure (BiPAP), interface used (nasal cannula, nasopharyngeal endotracheal tube, nasal mask, oronasal mask), mortality, and length of PICU stay. The indication for IMV or NIV was determined by the physician in charge of the patient based on clinical criteria. We performed the statistical analysis with the SPSS 21 software. Our analysis compared two periods of equal length, the first six years of the study (2001–2006) and the last six (2007–2012). We also compared children less and more than 3 months of age. We chose this cut-off point because this is the age threshold for risk reported by other studies. We compared frequencies and medians using the chi square test and Fisher's exact test. The level of statistical significance was set at p<.05.

Classic therapeutic measures indicated for bronchiolitis, such as aerosol therapy, humidity and physical therapy, have demonstrated poor effectiveness in the management of respiratory failure secondary to this illness.1–4

In recent years, NIV and high-flow oxygen therapy have gained importance in the management of children with bronchiolitis, and several studies have analysed its effects.5–18 Our study is the one that has analysed the outcomes of NIV characteristics (interfaces and modes) for the longest period of time, which allowed us to assess their effects on length of stay and need for IMV.

Our study found a significant increase in the number of PICU admissions for bronchiolitis in recent years1,19,20 as well as a more frequent use of NIV. This increase in NIV use was accompanied by a reduced need for IMV, consistent with other studies,3,7,21–23 and by a shorter length of stay in the PICU. These findings are highly significant and evince an important advance in treatment, as this can lead to decreased mortality and contribute to cost reduction, although our study did not analyse these variables.

In the second period under study, the percentage of patients with risk factors was significantly lower than in the first period. This may suggest that the severity of disease was greater in patients in the first period compared to patients in the second period, or that the indications for admission and treatment with NIV were different in both periods, with NIV being initiated earlier in recent years. Thus, we cannot rule out a bias in the indication for NIV, as our study did not analyse the degree of severity of respiratory failure prior to treatment with NIV. However, the reason for admission to the PICU and for using NIV was failure of other measures of respiratory support, and in the last period of the study many of the patients had been treated with high-flow oxygen in the hospital ward.

Patients treated with IMV had longer lengths of stay than patients that required NIV alone, results that are similar to those found in other studies.23 The duration of IMV was longer in the first period under study, and duration of NIV was longer in the second, although these differences did not reach statistical significance. These findings suggest that the use of NIV reduces the need for IMV and lengths of stay. However, given that we conducted a long-term retrospective study and that we did not assess the degree of severity of respiratory failure, we cannot rule out the influence of other factors in these findings.

The types of interface used in NIV changed throughout the study, with a progressive increase in the use of bilevel pressure modes that offer more support to the patient, and of nasal cannulae as an interface, which while offering less respiratory support are better tolerated by the patient. Consequently, nasal and oronasal masks have come to be used only in patients with more severe respiratory failure or when treatment with other interfaces fails. Other interfaces, such as helmets and full-face masks, were not used in this study.

Our results show that patients that receive NIV post extubation have longer lengths of stay in the PICU, which makes sense considering that they had previously required IMV, and thus had had more severe respiratory insufficiency. The length of stay was also longer in children treated with BiPAP. This is not to say that BiPAP is less effective than CPAP, and may be due to the bilevel pressure mode being used in children with more severe respiratory failure.

In children younger than 3 months, CPAP was the most frequently used type of NIV and endotracheal tubes were the most frequently used interface. This is because there are still few bilevel (BiPAP) NIV interfaces that adapt well to the smallest infants, and because these patients tolerate a shortened endotracheal tube placed in the nasopharynx through a nostril better than other children.24

In our study, contrary to what happened in others,1,2,16 patients younger than 3 months did not require IMV more frequently nor had higher lengths of stay or mortality. Our results show that NIV may be useful in children with bronchiolitis irrespective of their age. However, we must interpret these results with caution, as we cannot rule out the presence of a severity bias. Thus, large-scale prospective studies are required to confirm these findings.

We found a percentage of NIV failure that was lower than those described in other studies.2–4 This could be due to earlier initiation of NIV in patients with milder degrees of respiratory failure, but we could not confirm this hypothesis, as respiratory failure characteristics were not documented at the time NIV was initiated.

There are several limitations to our study. First, we did not compare patients receiving NIV with a control group. We believe that such a study would not be ethically justified at the moment. The most important limitation is that this was a retrospective study in which we could not document the severity of respiratory failure, which, as we mentioned, may influence our results. We were also unable to assess the effect of the NIV mode and interface used in each patient. Thus, prospective studies ought to be conducted that analyse the relationship between the severity of respiratory failure, NIV characteristics, and interface type used on the need for IMV and the length of stay in the PICU.

We have concluded that bronchiolitis is the cause of a considerable number of PICU admissions. In our experience, the increased use of NIV is associated with a reduced need for IMV and a shorter length of stay in the PICU.

The authors have no conflicts of interest to declare.