Oxygen therapy: appropriate use of nebulizers

Control of the inspired O2 concentration requires both an appropriate O2 fraction from the nebulizer and an adequate flow of gas to the patient. We evaluated the O2 fraction and total flow of commercially available nebulizers operated under conditions commonly encountered in clinical use. Total gas flow O2 fraction, and back pressure were measured in 8 commercially available nebulizers. Measurements were made with no outlet tubing ,with 72 inches of dry corrugated plastic tubing, and with 72 inches of corrugated plastic tubing partially occluded with water. Nebulizers were studied individually ,and in parallel sets of 2 and 3, at both 40% and 70% O2 settings. Total flow was always lower and O2 fraction higher than that predicted by the manufacture under all experimental circumstances. As the outlet resistance of the nebulizers increased, the O2 fraction increased and the total flow decreased. The O2 fraction was, in addition, increased with the addition of each nebulizer in parallel. Currently available nebulizers have operating characteristics that do not permit the easy administration of accurate O2 therapy.