Excessive or abnormally thick mucus is a hallmark of many chronic and acute respiratory diseases. In cystic fibrosis (CF), abnormal ion transport dehydrates airway secretions and impairs mucociliary clearance.
In bronchiectasis, chronically damaged airways trap mucus, perpetuating infection and inflammation. Even in otherwise healthy infants with viral bronchiolitis, small airways can become obstructed with viscous secretions.
Across these conditions, improving mucus clearance remains a central therapeutic goal. Alongside airway clearance techniques, bronchodilators, and mucolytic drugs, hypertonic saline nebulization has emerged as a low-cost, relatively simple adjunctive therapy.
What is hypertonic saline nebulization?
Hypertonic saline is a sterile saline solution with a higher salt concentration than normal body fluids. While “normal” saline used for inhalation is 0.9% sodium chloride, hypertonic formulations for nebulization typically range from 3% to 7% sodium chloride.
When nebulized, the solution is converted into a fine mist and inhaled through a mouthpiece or mask. Treatment can be delivered using jet, ultrasonic or mesh nebulizers. The goal is not systemic sodium loading, but local biophysical effects on the airway surface liquid and mucus layer.
Mechanism of action in the airways
Several complementary mechanisms explain why hypertonic saline can aid mucus clearance:
- Osmotic water movement: The increased salt concentration draws water into the airway lumen, increasing the volume of airway surface liquid. This helps rehydrate thick, dehydrated mucus.
- Changes in mucus rheology: By disrupting ionic cross-links and altering the ionic environment around mucins, hypertonic saline can reduce mucus viscosity and elasticity, making secretions less “sticky” and easier to mobilise.
- Enhanced mucociliary clearance: Improved hydration and rheology support more effective ciliary beating. In CF and bronchiectasis, studies have shown sustained increases in mucociliary clearance after inhalation of hypertonic saline.
- Augmented cough clearance: Hypertonic saline can trigger cough; while sometimes uncomfortable, this may help move secretions from smaller to larger airways where they can be expectorated.
Evidence in key clinical indications
Cystic fibrosis
Nebulized hypertonic saline is now an established adjunct in CF care. Randomised trials and meta-analyses in adolescents and adults have shown that regular use of 3–7% saline, typically twice daily, can improve lung function over the short term and reduce pulmonary exacerbation frequency over longer follow-up.
Some key findings:
- Short-term improvements in FEV₁ after several weeks of twice-daily hypertonic saline compared with isotonic saline.
- Reduction in exacerbations and days on antibiotics with sustained use, even when long-term FEV₁ differences are modest.
- Benefits observed across a range of disease severities, though tolerance and response can vary between individuals.
Hypertonic saline does not replace other CF therapies (such as CFTR modulators or DNAse) but can complement them as part of a multi-modal airway clearance regimen.
Non-CF bronchiectasis
In non-CF bronchiectasis, chronic infection and mucus retention drive a similar vicious cycle. Controlled studies suggest that regular inhalation of 7% hypertonic saline can improve lung function, health-related quality of life, and reduce health-care utilisation compared with isotonic saline.
Patients frequently report:
- Easier expectoration of sputum
- Reduced sensation of chest congestion
- Fewer infective exacerbations over time
Because bronchiectasis is heterogeneous, clinicians often individualise concentration and frequency based on tolerability and response.
Viral bronchiolitis in infants
In hospitalised infants with viral bronchiolitis, several trials have compared nebulized 3–7% hypertonic saline with normal saline. Many report shorter length of stay and faster improvement in clinical scores in the hypertonic saline groups, though findings are not completely uniform and practice varies by guideline.
In this setting, hypertonic saline is typically used:
- Under close monitoring
- In combination with suction and supportive care
- With strict attention to dosing and frequency in very young patients
As always, protocols should follow local paediatric and respiratory guidelines.
Concentration, dosing and treatment schedules
There is no single standard regimen for nebulized hypertonic saline, but common practice follows patterns from clinical trials and real-world use.
Concentrations of 3% are often chosen for younger children, more reactive airways, or when tolerability is a concern, while 7% is frequently used in cystic fibrosis and bronchiectasis for stronger mucus thinning when tolerated.
Typical doses are 3–5 mL per session, once or twice daily in chronic use, with frequency in acute settings (such as bronchiolitis) tailored to clinical status and local protocols.
Many patients receive a bronchodilator beforehand, and only sterile, preservative-free inhalation vials should be used.
Device choice: jet, ultrasonic and mesh nebulizers
Hypertonic saline can be delivered via different nebulizer technologies:
- Jet nebulizers: Widely available, low-cost devices using compressed gas to generate aerosol. They are robust but less portable and may require longer treatment times.
- Ultrasonic nebulizers: Use high-frequency vibrations to create aerosol. They can deliver high output but may heat the solution slightly, which is usually acceptable for saline.
- Mesh nebulizers: Vibrating-mesh devices push liquid through a micro-perforated membrane to generate a fine mist. They are compact, quiet, and suitable for home and travel use, which can improve adherence for patients on long-term hypertonic saline regimens.
Conclusion
Hypertonic saline nebulization is a practical, relatively low-cost adjunct to airway clearance in conditions where thick, tenacious mucus contributes to symptoms and exacerbations.
By increasing airway surface liquid and improving mucus rheology, regular treatment can enhance mucociliary and cough clearance in appropriately selected patients.
Clinical decisions regarding concentration, dosing, and frequency should be individualised, guided by existing evidence and local protocols, and revisited as new therapies emerge.
With careful patient selection, education, and monitoring, nebulized hypertonic saline can be a valuable component of comprehensive respiratory care.
