Abstract
Background: The airway acidifies in a variety of inflammatory lung diseases as measured by exhaled breath condensate (EBC). We have demonstrated in vitro that alkalization improves absorption of cationic bronchodilators, such as albuterol and tiotropium, both in airway epithelia and smooth muscle cells; however, the rationale of airway alkalization therapy is not fully understood.
Objective: The purpose of the study was to determine the effect of nebulized sodium bicarbonate (NaHCO3) solution on airway vascular smooth muscle function.
Methods: Ten healthy non-smoker volunteers participated in the study. To assay airway pH, EBC was collected pre- and post-administration of 4.2% NaHCO3 (pH=8.4). NaHCO3 induced CO2 production was evaluated with a real-time mass spectrometer gas analyzer by measuring Phase 1 and end-tidal CO2 levels during normal breathing, and breath-hold maneuvers for 5 and 15 sec. Airway vascular smooth muscle responses were assessed by measuring airway blood flow (Qaw).
Results: After NaHCO3 administration for 15 min using a heated ultrasonic nebulizer, EBC pH increased from 7.54±0.2 to 8.07±0.09 units (p<0.05). Pre- and post-treatment exhaled CO2 levels during normal breathing, and breath-hold maneuvers for 5 and 15 sec were not significantly different, suggesting no excessive CO2 generation from the breakdown of inhaled NaHCO3. NaHCO3 nebulization resulted in an increase of mean Qaw from 33.9±3.8 to 48.7±5.5 μl/min/ml (p<0.05).
Conclusion: Nebulized NaHCO3 can increase airway pH without significant effects on exhaled CO2 levels in healthy subjects. NaHCO3 induced increase in Qaw, together with elevated airway pH, could improve absorption of inhaled cationic bronchodilators.
- © 2012 ERS