Current concepts of the pathogenesis of RSV bronchiolitis

Continuous positive airway pressure (CPAP) for acute bronchiolitis in children

BACKGROUND

Acute bronchiolitis is one of the most frequent causes of emergency department visits and hospitalisation in children up to three years of age. There is no specific treatment for bronchiolitis except for supportive treatment, which includes ensuring adequate hydration and oxygen supplementation. Continuous positive airway pressure (CPAP) aims to widen the lungs' peripheral airways, enabling deflation of overdistended lungs in bronchiolitis. Increased airway pressure also prevents the collapse of poorly supported peripheral small airways during expiration. Observational studies report that CPAP is beneficial for children with acute bronchiolitis. This is an update of a review first published in 2015 and updated in 2019.

OBJECTIVES

To assess the efficacy and safety of CPAP compared to no CPAP or sham CPAP in infants and children up to three years of age with acute bronchiolitis.

SEARCH METHODS

We conducted searches of CENTRAL (2021, Issue 7), which includes the Cochrane Acute Respiratory Infections Group Specialised Register, MEDLINE (1946 to August 2021), Embase (1974 to August 2021), CINAHL (1981 to August 2021), and LILACS (1982 to August 2021) in August 2021. We also searched the US National Institutes of Health Ongoing Trials Register ClinicalTrials.gov and the World Health Organization (WHO) International Clinical Trials Registry Platform (ICTRP) for completed and ongoing trials on 26 October 2021.

SELECTION CRITERIA

We considered randomised controlled trials (RCTs), quasi-RCTs, cross-over RCTs, and cluster-RCTs evaluating the effect of CPAP in children with acute bronchiolitis.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed study eligibility, extracted data using a structured pro forma, analysed data, and performed meta-analyses. We used the Cochrane risk of bias tool to assess risk of bias in the included studies. We created a summary of the findings table employing GRADEpro GDT software.  MAIN RESULTS: We included three studies with a total of 122 children (62/60 in intervention/control arms) aged up to 12 months investigating nasal CPAP compared with supportive (or 'standard') therapy. We included one new trial (72 children) in the 2019 update that contributed data to the assessment of respiratory rate and the need for mechanical ventilation for this update. We did not identify any new trials for inclusion in the current update. The included studies were single-centre trials conducted in France, the UK, and India. Two studies were parallel-group RCTs, and one study was a cross-over RCT. The evidence provided by the included studies was of low certainty; we made an assessment of high risk of bias for blinding, incomplete outcome data, and selective reporting, and confidence intervals were wide. The effect of CPAP on the need for mechanical ventilation in children with acute bronchiolitis was uncertain due to risk of bias and imprecision around the effect estimate (risk difference -0.01, 95% confidence interval (CI) -0.09 to 0.08; 3 RCTs, 122 children; low certainty evidence). None of the trials measured time to recovery. Limited, low certainty evidence indicated that CPAP decreased respiratory rate (decreased respiratory rate is better) (mean difference (MD) -3.81, 95% CI -5.78 to -1.84; 2 RCTs, 91 children; low certainty evidence). Only one trial measured change in arterial oxygen saturation (increased oxygen saturation is better), and the results were imprecise (MD -1.70%, 95% CI -3.76 to 0.36; 1 RCT, 19 children; low certainty evidence). The effect of CPAP on change in arterial partial carbon dioxide pressure (pCO₂) (decrease in pCO₂ is better) was imprecise (MD -2.62 mmHg, 95% CI -5.29 to 0.05; 2 RCTs, 50 children; low certainty evidence). Duration of hospital stay was similar in both the CPAP and supportive care groups (MD 0.07 days, 95% CI -0.36 to 0.50; 2 RCTs, 50 children; low certainty evidence). Two studies did not report pneumothorax, but pneumothorax did not occur in one study. No studies reported occurrences of deaths. Several outcomes (change in partial oxygen pressure, hospital admission rate (from the emergency department to hospital), duration of emergency department stay, and need for intensive care unit admission) were not reported in the included studies.

AUTHORS' CONCLUSIONS

The use of CPAP did not reduce the need for mechanical ventilation in children with bronchiolitis, although the evidence was of low certainty. Limited, low certainty evidence suggests that breathing improved (a decreased respiratory rate) in children with bronchiolitis who received CPAP; this finding is unchanged from the 2015 review and 2019 update. Due to the limited available evidence, the effect of CPAP in children with acute bronchiolitis is uncertain for our other outcomes. Larger, adequately powered trials are needed to evaluate the effect of CPAP for children with acute bronchiolitis.

Continuous positive airway pressure (CPAP) for acute bronchiolitis in children

BACKGROUND

Acute bronchiolitis is one of the most frequent causes of emergency department visits and hospitalisation in children. There is no specific treatment for bronchiolitis except for supportive treatment, which includes ensuring adequate hydration and oxygen supplementation. Continuous positive airway pressure (CPAP) aims to widen the lungs' peripheral airways, enabling deflation of overdistended lungs in bronchiolitis. Increased airway pressure also prevents the collapse of poorly supported peripheral small airways during expiration. Observational studies report that CPAP is beneficial for children with acute bronchiolitis. This is an update of a review first published in 2015.

OBJECTIVES

To assess the efficacy and safety of CPAP compared to no CPAP or sham CPAP in infants and children up to three years of age with acute bronchiolitis.

SEARCH METHODS

We conducted searches of CENTRAL (2017, Issue 12), which includes the Cochrane Acute Respiratory Infections Group's Specialised Register, MEDLINE (1946 to December, 2017), Embase (1974 to December 2017), CINAHL (1981 to December 2017), and LILACS (1982 to December 2017) in January 2018.

SELECTION CRITERIA

We considered randomised controlled trials (RCTs), quasi-RCTs, cross-over RCTs, and cluster-RCTs evaluating the effect of CPAP in children with acute bronchiolitis.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed study eligibility, extracted data using a structured pro forma, analysed data, and performed meta-analyses.

MAIN RESULTS

We included three studies with a total of 122 children (62/60 in intervention/control arms) aged up to 12 months that investigated nasal CPAP compared with supportive (or "standard") therapy. We included one new trial (72 children) that contributed data to the assessment of respiratory rate and need for mechanical ventilation for this update. The included studies were single-centre trials conducted in France, the UK, and India. Two studies were parallel-group RCTs and one was a cross-over RCT. The evidence provided by the included studies was low quality; we assessed high risk of bias for blinding, incomplete outcome data, and selective reporting, and confidence intervals were wide.The effect of CPAP on the need for mechanical ventilation in children with acute bronchiolitis was uncertain due to imprecision around the effect estimate (3 RCTs, 122 children; risk ratio (RR) 0.69, 95% confidence interval (CI) 0.14 to 3.36; low-quality evidence). None of the trials measured time to recovery. Limited, low-quality evidence indicated that CPAP decreased respiratory rate (2 RCTs, 91 children; mean difference (MD) -3.81, 95% CI -5.78 to -1.84). Only one trial measured change in arterial oxygen saturation, and the results were imprecise (19 children; MD -1.70%, 95% CI -3.76 to 0.36). The effect of CPAP on change in arterial partial carbon dioxide pressure (pCO₂) was imprecise (2 RCTs, 50 children; MD -2.62 mmHg, 95% CI -5.29 to 0.05; low-quality evidence). Duration of hospital stay was similar in both CPAP and supportive care groups (2 RCTs, 50 children; MD 0.07 days, 95% CI -0.36 to 0.50; low-quality evidence). Two studies did not report about pneumothorax, but pneumothorax did not occur in one study. No studies reported occurrences of deaths. Several outcomes (change in partial oxygen pressure, hospital admission rate (from emergency department to hospital), duration of emergency department stay, and need for intensive care unit admission) were not reported in the included studies.

AUTHORS' CONCLUSIONS

Limited, low-quality evidence suggests that breathing improved (a decreased respiratory rate) in children with bronchiolitis who received CPAP; this finding is unchanged from the 2015 review. Further evidence for this outcome was provided by the inclusion of a low-quality study for the 2018 update. Due to the limited available evidence, the effect of CPAP in children with acute bronchiolitis is uncertain for other outcomes. Larger, adequately powered trials are needed to evaluate the effect of CPAP for children with acute bronchiolitis.

RSV infection among children born moderately preterm in a community-based cohort

We aimed to determine the rates of proven respiratory syncytial virus (RSV) hospitalization and disease severity among children born moderately preterm (MP, gestational age [GA] 32-36 weeks, n = 964), children born full-term (FT, GA 38-42 weeks, n = 572), and children born early preterm (EP, GA <32 weeks, n = 524). Our second aim was to identify risk factors for RSV hospitalization among MP. We extracted data from parental questionnaires and medical records, retrieved from a community-based cohort of children aged 43-49 months. The RSV hospitalization rates of MP were higher than FT (3.9 vs. 1.2 %, relative rate 3.2; 95 % confidence interval (CI) 1.4-7.1) and equal to EP (3.9 vs. 3.2 %, relative rate 1.2; 95 % CI 0.7-2.1). MP were hospitalized at an earlier age than EP. Disease severity (based on the type of treatment and hospitalization length) was equal in all groups. Risk factors for RSV hospitalization in MP were younger age and lower birth weight. In multivariable analyses, shorter GA and passive smoking independently increased the likelihood of RSV hospitalization in MP.

CONCLUSION

The rates of hospitalization due to proven RSV infection are higher in MP than FT and not different between MP and EP. No difference in disease severity was observed. Among MP, the rates of RSV hospitalization are higher for lower GA and when exposed to passive smoking.

Interferon lambda 1-3 expression in infants hospitalized for RSV or HRV associated bronchiolitis

OBJECTIVES

The airway expression of type III interferons (IFNs) was evaluated in infants hospitalized for respiratory syncytial virus (RSV) or rhinovirus (HRV) bronchiolitis. As an additional objective we sought to determine whether a different expression of IFN lambda 1-3 was associated with different harboring viruses, the clinical course of bronchiolitis or with the levels of well established IFN stimulated genes (ISGs), such as mixovirus resistance A (MxA) and ISG56.

METHODS

The analysis was undertaken in 118 infants with RSV or HRV bronchiolitis. Nasopharyngeal washes were collected for virological studies and molecular analysis of type III IFN responses.

RESULTS

RSV elicited higher levels of IFN lambda subtypes when compared with HRV. A similar expression of type III IFN was found in RSVA or RSVB infected infants and in those infected with HRVA or HRVC viruses. Results also indicate that IFN lambda 1 and IFN lambda 2-3 levels were correlated with each other and with MxA and ISG56-mRNAs. In addition, a positive correlation exists between the IFN lambda1 levels and the clinical score index during RSV infection. In particular, higher IFN lambda 1 levels are associated to an increase of respiratory rate.

CONCLUSIONS

These findings show that differences in the IFN lambda 1-3 levels in infants with RSV or HRV infections are present and that the expression of IFN lambda 1 correlates with the severity of RSV bronchiolitis.

Prevention and prophylaxis of respiratory syncytial virus in pediatric cardiology: a UK perspective

ABSTRACT: 

Respiratory syncytial virus (RSV) is a common infection, causing bronchiolitis in over 70% of infants each year and almost all children by the age of 2. It is the leading cause of acute lower respiratory tract infections and admissions to hospital worldwide. Previously healthy infants may have a prolonged cough or wheezing following RSV infection but up to 20% of those with congenital cardiac disease will be hospitalized and have significant morbidity and mortality. For this reason, it is generally recommended that many such infants should receive prophylaxis against RSV infection with palivizumab. This paper reviews the current state of knowledge about RSV affecting children with congenital heart disease from the perspective of those living in the UK and the current protection offered to such children. We also discuss the plans for the future of protection against RSV.

Respiratory syncytial virus vaccine development

The importance of RSV as a respiratory pathogen in young children made it a priority for vaccine development shortly after it was discovered. Unfortunately, after over 50 years of vaccine development no vaccine has yet been licensed and it is not certain which if any vaccines being developed will be successful. The first candidate vaccine, a formalin inactivated RSV vaccine (FI-RSV), was tested in children in the 1960s and predisposed young recipients to more serious disease with later natural infection. The ongoing challenges in developing RSV vaccines are balanced by advances in our understanding of the virus, the host immune response to vaccines and infection, and pathogenesis of disease. It seems likely that with efficient and appropriately focused effort a safe and effective vaccine is within reach. There are at least 4 different target populations for an RSV vaccine, i.e. the RSV naïve young infant, the RSV naïve infant >4-6 months of age, pregnant women, and elderly adults. Each target population has different issues related to vaccine development. Numerous vaccines from live attenuated RSV to virus like particle vaccines have been developed and evaluated in animals. Very few vaccines have been studied in humans and studies in humans are needed to determine which vaccines are worth moving toward licensure. Some changes in the approach may improve the efficiency of evaluating candidate vaccines. The complexity of the challenges for developing RSV vaccines suggests that collaboration among academic, government, and funding institutions and industry is needed to most efficiently achieve an RSV vaccine.

Glucocorticoids for acute viral bronchiolitis in infants and young children

BACKGROUND

Previous systematic reviews have not shown clear benefit of glucocorticoids for acute viral bronchiolitis, but their use remains considerable. Recent large trials add substantially to current evidence and suggest novel glucocorticoid-including treatment approaches.

OBJECTIVES

To review the efficacy and safety of systemic and inhaled glucocorticoids in children with acute viral bronchiolitis.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL 2012, Issue 12), MEDLINE (1950 to January week 2, 2013), EMBASE (1980 to January 2013), LILACS (1982 to January 2013), Scopus® (1823 to January 2013) and IRAN MedEx (1998 to November 2009).

SELECTION CRITERIA

Randomised controlled trials (RCTs) comparing short-term systemic or inhaled glucocorticoids versus placebo or another intervention in children under 24 months with acute bronchiolitis (first episode with wheezing). Our primary outcomes were: admissions by days 1 and 7 for outpatient studies; and length of stay (LOS) for inpatient studies. Secondary outcomes included clinical severity parameters, healthcare use, pulmonary function, symptoms, quality of life and harms.

DATA COLLECTION AND ANALYSIS

Two authors independently extracted data on study and participant characteristics, interventions and outcomes. We assessed risk of bias and graded strength of evidence. We meta-analysed inpatient and outpatient results separately using random-effects models. We pre-specified subgroup analyses, including the combined use of bronchodilators used in a protocol.

MAIN RESULTS

We included 17 trials (2596 participants); three had low overall risk of bias. Baseline severity, glucocorticoid schemes, comparators and outcomes were heterogeneous. Glucocorticoids did not significantly reduce outpatient admissions by days 1 and 7 when compared to placebo (pooled risk ratios (RRs) 0.92; 95% confidence interval (CI) 0.78 to 1.08 and 0.86; 95% CI 0.7 to 1.06, respectively). There was no benefit in LOS for inpatients (mean difference -0.18 days; 95% CI -0.39 to 0.04). Unadjusted results from a large factorial low risk of bias RCT found combined high-dose systemic dexamethasone and inhaled epinephrine reduced admissions by day 7 (baseline risk of admission 26%; RR 0.65; 95% CI 0.44 to 0.95; number needed to treat 11; 95% CI 7 to 76), with no differences in short-term adverse effects. No other comparisons showed relevant differences in primary outcomes.

AUTHORS' CONCLUSIONS

Current evidence does not support a clinically relevant effect of systemic or inhaled glucocorticoids on admissions or length of hospitalisation. Combined dexamethasone and epinephrine may reduce outpatient admissions, but results are exploratory and safety data limited. Future research should further assess the efficacy, harms and applicability of combined therapy.

Th1 and th2 cytokine expression in nasopharyngeal secretions during acute bronchiolitis in children younger than two years old

OBJECTIVES

We characterised the T helper cytokine profiles on the surface of nasal mucosa of children with acute bronchiolitis caused by Respiratory Syncytial Virus, Parainfluenza Virus, Influenza Virus, Adenovirus, or without any viral identification, in order to examine whether these viral types modified cytokine responses. As an additional objective we sought to determine if T helper polarisation was associated with other demographic and environmental factors.

METHODS

A prospective study of children with acute bronchiolitis was performed. Patients were recruited from the emergency department of a central hospital in Lisbon, Portugal. Demographical, epidemiological and clinical data were gathered from a questionnaire. Nasal swabs were collected for viral studies (immunofluorescence) and T cell cytokine responses (detection of expression of interleukins 4, 13, 12 and interferon-γ by real-time polymerase chain reaction assays).

RESULTS

Respiratory Syncytial Virus elicited lower levels of interleukin 4, when compared with samples without virus identification. A similar tendency to Th1 polarisation was found in older children, in those who attended day-care centres, and in breastfed individuals. Exposure to tobacco smoke was associated with a Th2 bias in this population.

CONCLUSIONS

These findings show that Respiratory Syncytial Virus infection contributes to Th1 polarisation in immune response of respiratory mucosa, an effect that is similar to other environmental factors. Further studies are needed to assess immune response to other infectious causes of acute bronchiolitis.

Glucocorticoids for acute viral bronchiolitis in infants and young children

BACKGROUND

Previous systematic reviews have not shown clear benefit of glucocorticoids for acute viral bronchiolitis, but their use remains considerable. Recent large trials add substantially to current evidence and suggest novel glucocorticoid-including treatment approaches.

OBJECTIVES

To review the efficacy and safety of systemic and inhaled glucocorticoids in children with acute viral bronchiolitis.

SEARCH STRATEGY

We searched the Cochrane Central Register of Controlled Trials (The Cochrane Library 2009, issue 4); MEDLINE (1950 to November 2009); EMBASE (1980 to Week 47 2009); LILACS (1982 to November 2009); Scopus® (1823 to November 2009); and IRAN MedEx (1998 to November 2009).

SELECTION CRITERIA

Randomised controlled trials (RCTs) comparing short-term systemic or inhaled glucocorticoids versus placebo or another intervention in children < 24 months with acute bronchiolitis (first episode with wheezing). Our primary outcomes were: admissions by days 1 and 7 for outpatient studies; and length of stay (LOS) for inpatient studies. Secondary outcomes included clinical severity parameters, healthcare use, pulmonary function, symptoms, quality of life and harms.

DATA COLLECTION AND ANALYSIS

Two authors independently extracted data on study and participant characteristics, interventions and outcomes. We assessed risk of bias and graded strength of evidence. Inpatient and outpatient results were meta-analysed separately using random-effects models. We pre-specified subgroup analyses, including the combined use of protocolised bronchodilators.

MAIN RESULTS

We included 17 trials (2596 participants); only two had low overall risk of bias. Baseline severity, glucocorticoid schemes, comparators and outcomes were heterogeneous. Glucocorticoids did not significantly reduce outpatient admissions by days 1 and 7 when compared to placebo (pooled risk ratios (RRs) 0.92; 95% CI 0.78 to 1.08; and 0.86; 95% CI 0.7 to 1.06, respectively). There was no benefit in LOS for inpatients (mean difference -0.18 days; 95% CI -0.39 to 0.04). Unadjusted results from a large factorial low risk of bias RCT found combined high-dose systemic dexamethasone and inhaled epinephrine reduced admissions by day 7 (baseline risk of admission 26%; RR 0.65, 95% CI 0.44 to 0.95; number needed to treat 11, 95% CI 7 to 76), with no differences in short-term adverse effects. No other comparisons showed relevant differences in primary outcomes.

AUTHORS' CONCLUSIONS

Current evidence does not support a clinically relevant effect of systemic or inhaled glucocorticoids on admissions or length of hospitalization. Combined dexamethasone and epinephrine may reduce outpatient admissions, but results are exploratory and safety data limited. Future research should further assess the efficacy, harms and applicability of combined therapy.