Objective: To evaluate nebulizer performance when
heliox was used to power the nebulizer.
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 μm (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.
Abbreviations: GSD = geometric SD; MMAD = mass
median aerodynamic diameter