A Comparison of Pulmonary Functions, Before and After Bronchodilator, Using Small- and Large-Particle Nebulizers, Driven with Either Air or 80%He - 20% 02 on Patients with Reversible Airways Disease

Abstract

The comparison of pulmonary functions is used frequently in evaluating patient response to aerosol bronchodilators. The usual method for delivery of aerosol bronchodilators employs some arbitrarily chosen nebulizer driven by air or oxygen at some arbitrarily selected flow-rate. Although the science of medical aerosol production and particle size distribution remains confusing, several attempts have been made at evaluation of the generating devices. On the other hand, an objective evaluation of the carrier gas used in this therapy has up to now been lacking. The micron range of particle size has been measured and reported in a multitude of ways. Various investigators have reported measuring particle size using such expressions as mass median aerodynamic diameter, median particle diameter, mass median diameter, volume median droplet diameter, and mean particle diameter. Non-uniformity makes comparison almost impossible. Weiner has stated, "the questions needing definitive answers are predominantly biologic, not engineering." She believes these questions include: What particles and what medication can be directed in what quantity to the respiratory tracts of patients with what diseases at what spectra of particle size? Some authors have claimed that using 80%helium-20%oxygen would be ineffective because the low density of the helium mixture made them poorer vehicles for transport of the aerosol particles. Motley, on the other hand, has inferred that the use of helium-oxygen mixtures in aerosol therapy might be indicated in patients with upper airway obstruction. Opinions abound in regard to this matter, but facts are scarce. In this. study ,we hope, at least indirectly, to address some of these questions. We have examined physiological responses of .the airways of patients with airflow obstructive disorders to the administration of a sympathomimetic agonist aerosol from both large-particle and small-particle nebulizers. We have compared the effects of a low-density gas mixture with air as carrier-gases for aerosol therapy by using ventilatory function tests to assess the responses of the airways to the bronchodilator drugs given in this manner. We expected to find that the air-driven, small-particle nebulizer would produce the greatest response per volume of bronchodilator administered in both routine spirometry and VisoV analysis. We also expected 80%He-20%02 because of its lower density, .to be a poorer carrier-gas than air and result in poorer bronchodilator responsiveness.