Saline Concentration for Nebulization to Assist Expectoration
0.9% sodium chloride (normal saline) is the standard concentration used for nebulization to assist with expectoration and physiotherapy. 1
Standard Protocol
0.9% normal saline is specifically recommended by the British Thoracic Society for nebulization to assist physiotherapy and sputum clearance. 1
The typical volume administered is 5 mL of 0.9% sodium chloride given every 6 hours when used to loosen tenacious secretions in palliative care settings. 1
For sputum induction procedures, a 2.7% hypertonic saline solution (1 mmol/mL) in volumes of 20-30 mL is used with high-output ultrasonic nebulizers, though this is specifically for diagnostic sputum collection rather than routine expectoration assistance. 1
Critical Safety Consideration
- Water should never be used as a nebulizing solution because it may cause bronchoconstriction when nebulized. 1 This is a common and potentially dangerous error to avoid.
Evidence for Hypertonic Saline
While 0.9% isotonic saline is the guideline-recommended standard, research evidence suggests that 7% hypertonic saline may be more effective than isotonic saline for promoting sputum expectoration in patients with bronchiectasis (median difference 3.7 g vs isotonic saline), though it carries a higher risk of adverse effects. 2 However, guidelines have not yet incorporated this as standard practice for routine expectoration assistance.
Administration Details
Minimum dilution volume of 2-3 mL of normal saline is required for adequate nebulization across all age groups. 3
Oxygen is the preferred driving gas for nebulization at flow rates of 6-8 L/min, though compressed air can be used when oxygen is not indicated. 1
For patients requiring humidification with high-flow oxygen or those with viscous sputum retention, large volume nebulizer-based humidifiers delivering 0.9% saline can assist with expectoration, though evidence for this practice is based on expert opinion rather than randomized trials. 1