Stratified assessment of the role of inhaled hypertonic saline in reducing cystic fibrosis pulmonary exacerbations: a retrospective analysis

Abstract

Objective

Limited data exist concerning the role of inhaled hypertonic saline (HS) in decreasing pulmonary exacerbations in cystic fibrosis (CF), especially as more advanced stages of CF lung disease were excluded in prior studies. Herein, the authors retrospectively determined the efficacy of inhaled HS in reducing CF pulmonary exacerbations when stratified according to the severity of CF lung disease. Stratification was based on the framework of the Pulmonary Therapeutics Committee's published gradation of obstructive lung physiology in CF, that is, mild (FEV ₁ >70%), moderate (FEV ₁ 40–70%) and severe (FEV ₁ <40%) lung disease, respectively.

Design

A retrospective review of the Port CF database over a 3-year period performed at an academic CF care centre.

Results

340 pulmonary exacerbations were identified; inhaled HS was being used in 99 of these cases. Univariate analysis demonstrated a significant reduction in pulmonary exacerbations only in mild obstruction (OR=0.09, CI 0.01 to 0.81, p=0.012); however, multivariate logistic regression that adjusted for confounding variables showed a reduction in pulmonary exacerbations across the entire spectrum of obstructive lung disease when using inhaled HS, that is, mild obstructive CF lung disease (OR=0.17, CI 0.05 to 0.58, p=0.004), moderate obstructive CF lung disease (OR=0.39, CI 0.16 to 0.93, p=0.034), as well as severe obstructive CF lung disease (OR=0.02, CI 0.001 to 0.45, p=0.015). Moreover, inhaled HS appeared reasonably well tolerated across all stages of lung-disease severity, and was discontinued in only 7% of cases (n=4) with severe lung disease.

Conclusion

In this study, inhaled HS appeared to reduce pulmonary exacerbations in CF lung disease at all stages of obstruction. This underscores the importance of therapeutic inhaled HS in CF lung disease, regardless of the severity of lung obstruction.

Article summary

Article focus

• Prior studies have demonstrated that inhaled hypertonic saline (HS) improves the forced expiratory volume in 1 s (FEV ₁) and the forced vital capacity (FVC) in patients with cystic fibrosis.

• Inhaled HS also decreases the frequency of pulmonary exacerbations in cystic fibrosis; this aspect has been less extensively studied, especially in more severe forms of disease.

• This study focuses on the role of inhaled HS in decreasing the frequency of pulmonary exacerbations in patients stratified according to the severity of CF lung disease.

Key messages

• This study suggests that inhaled HS may be beneficial in reducing pulmonary exacerbations at all stages of CF lung disease severity, thus highlighting the importance of inhaled HS as a key component of the CF therapeutic armamentarium.

• The observed benefit of inhaled HS appeared in addition to that of established airway clearance strategies such as nebulised rhDNase therapy and mechanical airway clearance devices.

• This study found no indication of any excessive discontinuation of inhaled HS due to cough or bronchospasm in more severe forms of CF lung disease, suggesting that it is reasonably well tolerated even in such cases.

Strengths and limitations of this study

• This study establishes the role of inhaled HS in reducing the number of pulmonary exacerbations at more advanced stages of CF lung disease severity, which is of special significance considering that the more severe forms of CF lung disease had been excluded in previous studies.

• Our study group had a significantly higher usage of nebulised rhDNase (100%) and other mechanical airway clearance therapies (97%) compared with previous studies, thus supporting the additional beneficial effect of inhaled HS.

• Our two study groups had differences in epidemiological characteristics, potentially introducing bias into the results. We have attempted to minimise for this by performing a logistic regression; however, we acknowledge the inherent limitations of such a retrospective study design.