Shortcomings of using two jet nebulizers in tandem with an aerosol face mask for optimal oxygen therapy.

Herein, a laboratory model which allows measurement of simulated distal airway oxygen percentage at different breathing patterns is described to illustrate the shortcomings of conventional O2 devices and, in particular, the aerosol face mask with two jet nebulizers (AFM-DF) in tandem. A table showing the degree of dilution which occurred during simulation of various breathing patterns while using the AFM-DF is also presented. Data revealed that when 60 percent was desired, 13 of 27 measurements were less than 55 percent. The worst-case scenario for 60 percent desired was 48 percent measured. When 80 percent was desired, less than 70 percent was delivered in 24 of the 27 breathing patterns simulated. Less than 60 percent was measured on 12 occasions, with 51 percent being the lowest measurement. When 100 percent O2 was desired, less than 80 percent was measured in 25 of 27 breathing patterns. Less than 60 percent was measured in ten of those. Fifty percent was the lowest analyzed value for the 100 percent setting. The inadequacy of AFM-DF is described in three case studies. A high-flow nonrebreathing face mask (HFM) to address the subset of patients is also discussed. A peak inspiratory flow prediction chart is also documented and may be useful in setting optimal flows when using high-flow systems. The patients in whom intubation and mechanical ventilation (or use of continuous mask CPAP) are indicated can be more clearly identified with a trial of high-flow O2 therapy (with a system that assures adequate flow to meet the patient's peak inspiratory flow demands). In the remainder of patients, those higher-risk modalities will be precluded.