Diluting Medications in PNSS Nebules
The drug solution should be diluted to fill the nebulizer to capacity, typically 2.0-4.5 mL total volume, with most modern nebulizers requiring 2-2.5 mL to account for the 0.5 mL residual volume that remains after nebulization. 1
Standard Dilution Volumes
For bronchodilators (β-agonists, ipratropium): Add preservative-free normal saline (PNSS) to achieve a total volume of 2-2.5 mL in modern nebulizers that leave 0.5 mL residual, or up to 4.5 mL in older models 1
Bronchodilators can be mixed together (e.g., β-agonists and ipratropium bromide) in the same nebule with PNSS to make up the total volume of 4.5 mL 1
For antibiotics, steroids, and pentamidine: Dilute to fill the nebulizer to full capacity as these medications require longer nebulization times to maximize drug delivery 1
Evidence-Based Volume Considerations
Increasing fill volume significantly improves drug delivery to the patient. Research demonstrates that larger fill volumes decrease the amount of medication trapped in dead space (p < 0.001) and increase the amount delivered to the patient (p < 0.001) 2
When 2.5 mg of albuterol was tested, less than 0.5 mg in the respirable range (1-5 microns) actually reached the mouthpiece, emphasizing the importance of adequate dilution volume 2
For hypertonic saline treatments: Use 4.0 mL of 3% hypertonic saline mixed with 0.5 mL (2.5 mg) of salbutamol for conditions like bronchiolitis 3
Critical Technical Parameters
Gas flow rate: Use 6-8 L/min to nebulize 50% of particles to 2-5 μm diameter for optimal small airway deposition 1
Nebulization time: 10 minutes is sufficient for bronchodilators; antibiotics and steroids may require longer 1
Never use water as a diluent—it may cause bronchoconstriction when nebulized. Only use 0.9% sodium chloride (PNSS) 1
Drug-Specific Compatibility
Ipratropium bromide can be mixed in the nebulizer with albuterol or metaproterenol if used within one hour, but not with other drugs. 4 Drug stability and safety when mixed with other medications have not been established beyond these combinations 4
Mechanical Ventilation Context
For mechanically ventilated patients, the drug solution should be diluted to fill the nebulizer to capacity regardless of nebulizer type (jet or ultrasonic), and humidification must be discontinued for a few minutes before and throughout nebulization 1