Objective: To evaluate nebulizer performance when heliox was used to power the nebulizer.
Methods: Conventional and continuous nebulizer designs were evaluated. The conventional nebulizer was used with 5 mg albuterol and flows of 8 L/min air, 8 L/min heliox, and 11 L/min heliox; it was also used with 10 mg albuterol and a heliox flow of 8 L/min. The continuous nebulizer was set to deliver 10 mg of albuterol over 40 min at flows of 2 L/min air, 2 L/min heliox, and 3 L/min heliox; it was also used with 20 mg albuterol and a heliox flow of 2 L/min. A cotton plug at the nebulizer mouthpiece was used to trap aerosol during simulated spontaneous breathing. The amount of albuterol deposited on the cotton plug was determined spectrophotometrically. Particle size was determined using an 11-stage cascade impactor.
Results: For both nebulizer designs, particle size and inhaled mass of albuterol decreased significantly (p < 0.001) when the nebulizer was powered with heliox rather than air. When powered with heliox, the reduction in inhaled mass of albuterol was less for the conventional nebulizer (16%) than the continuous nebulizer (67%). The nebulization time, however, was more than twofold greater with heliox (p < 0.001). Increasing the flow of heliox increased the particle size (p < 0.05), inhaled mass of albuterol (p < 0.05), and inhaled mass of particles 1 to 5 microm (p < 0.05) to levels similar to powering the nebulizer with air at the lower flow. Increasing the albuterol concentration in the nebulizer and using the lower heliox flow increased the inhaled mass of albuterol (p < 0.05) while maintaining the smaller particle size produced with that flow.
Conclusions: The use of heliox to power a nebulizer affects both the inhaled mass of medication and the size of the aerosol particles. The flow to power the nebulizer should be increased when heliox is used.