title: Improvement in aerosol delivery with helium-oxygen mixtures during mechanical ventilation.
abstract: In mechanically ventilated patients with airway obstruction, helium-oxygen (He-O2) mixtures reduce airway resistance and improve ventilation, but their influence on aerosol delivery is unknown. Accordingly, we determined the effect of various He-O2 mixtures on albuterol delivery from metered-dose inhalers (MDIs) and jet nebulizers in an in vitro model of mechanical ventilation. Albuterol delivery from a MDI was increased when the ventilator circuit contained 80% helium and 20% oxygen (He-O2 80/20) versus O2: 46.7 +/- 3.3 versus 30.2 +/- 1.3 (SE)% of the nominal dose (p < 0.001)-the difference was mainly due to decreased drug deposition in the spacer chamber, mean 39.2% and 55.2%, respectively (p < 0.001). Nebulizer efficiency at a flow rate of 6 L/min was five times lower with He-O2 80/20 than O2, and the amount of nebulized drug was inversely correlated with gas density (r = 0.94, p < 0.0001). When the nebulizer was operated with O2, greater albuterol delivery was achieved when the ventilator circuit contained He-O2 rather than O2. In summary, He-O2 mixtures in the circuit increased aerosol delivery for both MDIs and nebulizers in the mechanically ventilated model by as much as 50%. In conclusion, at appropriate flow rates and concentrations, He-O2 in the ventilator circuit may improve aerosol delivery in mechanically ventilated patients with severe airway obstruction.
authors.affiliation: Division of Pulmonary and Critical Care Medicine, Edward Hines Jr. Veterans Affairs Hospital, and Loyola University of Chicago Stritch School of Medicine, Hines, Illinois, USA.
authors.forename: M L
authors.initials: ML
authors.lastname: Goode
authors.forename: J B
authors.initials: JB
authors.lastname: Fink
authors.forename: R
authors.initials: R
authors.lastname: Dhand
authors.forename: M J
authors.initials: MJ
authors.lastname: Tobin
mesh_terms: D000336:Aerosols / Q000008:administration & dosage; D006371:Helium / Q000008:administration & dosage*; D010100:Oxygen / Q000008:administration & dosage*; D012121:Respiration, Artificial
chemical_list: D000336:Aerosols; D006371:Helium; D010100:Oxygen