Mucolytics for children with chronic suppurative lung disease.

BACKGROUND

Chronic suppurative lung disease (CSLD) is an umbrella term to define the spectrum of endobronchial suppurative lung disease, including bronchiectasis and protracted bacterial bronchitis (PBB), associated with chronic wet or productive cough. Research that explores new therapeutic options in children with CSLD has been identified by clinicians and patients as one of the top research priorities. Mucolytic agents work to improve mucociliary clearance and interrupt the vicious vortex of airway infection and inflammation, hence they have potential as a therapeutic option.

OBJECTIVES

To assess the effects of mucolytics for reducing exacerbations, improving quality of life and other clinical outcomes in children with CSLD (including PBB and bronchiectasis), and to assess the risk of harm due to adverse events.

SEARCH METHODS

An Information Specialist searched the Cochrane Airways Trials Register to June 2022, and a review author searched the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE and Embase databases to 27 September 2024. Other review authors handsearched respiratory journals.

SELECTION CRITERIA

We included randomised controlled trials (RCTs), of both cross-over and parallel design, that compared a mucolytic with a placebo or 'no intervention' control group and included children (aged 18 years and under) with any type of CSLD (including PBB and bronchiectasis). We excluded studies with adult participants and studies in children with cystic fibrosis, empyema, pulmonary abscess or bronchopulmonary fistula.

DATA COLLECTION AND ANALYSIS

Two authors independently reviewed titles and abstracts to assess eligibility for inclusion. The authors then assessed study quality and extracted data. They assessed the quality of the study using the Cochrane risk of bias tool (RoB 2), and used GRADE to assess the certainty of evidence. Outcomes of interest to be analysed included: i) for maintenance or stable state: rate of exacerbations, ii) for exacerbation state: time to resolution of respiratory exacerbation, iii) lung function - forced expiratory volume in one second (FEV) and forced vital capacity (FVC), iv) quality of life and v) adverse events. Only one study met the inclusion criteria, so we could not perform a meta-analysis. Data were continuous, so we reported outcomes as mean differences.

MAIN RESULTS

The sole included RCT was a cross-over study of 63 children in the total cohort, with reported data and analysis of only 52 children (26 per arm) with non-cystic fibrosis bronchiectasis. The study compared 3% hypertonic saline nebulised before chest physiotherapy with a control arm (physiotherapy alone), with each phase lasting eight weeks. Children in the hypertonic saline arm had a mean age of 9.80 (SD 2.97) years and 42.3% were male; those in the control arm had a mean age of 9.10 (SD 2.40) years and 38.4% were male. Only results of the first arm of the cross-over study were included in this review. The RCT reported a clinically important difference between the groups for our review's primary outcome: rate of respiratory exacerbations. The mean number of exacerbations per child-year was 2.50 (SD 0.64) in the intervention group and 7.80 (SD 1.05) in the control group (mean difference (MD) -5.30, 95% CI -5.77 to -4.83; 1 study, 52 participants; very low-certainty evidence). The RCT also reported that the percentage point improvement in mean % predicted FEV and FVC from baseline to week eight was better with hypertonic saline compared to control. Mean FEV improvement was 14.15% (SD 5.50) in the intervention group versus 5.04% (SD 5.55) in the control group (MD 9.11%, 95% CI 6.11 to 12.11; 1 study, 52 participants; very low-certainty evidence). While for FVC, the mean improvement was 13.77% (SD 5.73) compared with 7.54% (SD 4.90), respectively (MD 6.23%, 95% CI 3.33 to 9.13; 1 study, 52 participants; very low-certainty evidence). Quality of life measures were not used. We judged the study to have a high risk of bias due to unblinding, missing data, deviation from the intended intervention and reporting bias with measurement and selection of outcome measures. The authors reported that there were no dropouts due to adverse events. No data were available regarding quality of life. The included study assessed mucolytic use during a stable state, and we found no studies of mucolytic use during an exacerbation. We also found no studies assessing oral mucolytics, other inhaled mucolytics, use in PBB, or in settings other than hospital outpatients. We also found two ongoing studies, one using hypertonic saline and one using an oral mucolytic agent erdosteine, which will potentially be included in future updates of this review.

AUTHORS' CONCLUSIONS: This systematic review is limited to a single small study, which we judged to be at high risk of bias. It remains uncertain whether regular nebulised hypertonic saline during a stable state reduces exacerbations or improves lung function. Further multi-centre, well-designed RCTs of longer duration that investigate various mucolytics are required to answer this important clinical question.