The Science Journal of the American Association for Respiratory Care

2004 OPEN FORUM Abstracts

THE DHD HEALTHCARE HIGH-FLOW NEBULIZER MAINTAINS HIGH CONCENTRATION OF INTRATRACHEAL FIO2 IN SIMULATED BREATHING UP TO VE OF 25 L/MIN

Ali AY, Hotopp TY, Mason KS, Newman GH, Sutherland TM, Ward JJ, RRT, Findlay, JY, Plevak DJ. Rochester Community & Technical College-Mayo Clinic College of Medicine, Rochester, MN

Background: Certain clinical situations require non-invasive administration of high flow and oxygen concentration (FIO2) in spontaneously breathing patients. A new high flow nebulizer is being manufactured by DHD Healthcare Inc.(Wampsville, NY) [high-flow barrel nebulizer # P30000H]. DHD specifies that the nebulizer can deliver FIO2 of 0.85 or greater when set at 0.95 (nebulizer's highest setting). They suggest that output flows are sufficient to meet patient demands and mitigate problems of lower flow output oxygen delivery systems. We used a mannequin model to simulate 4 high flow demand situations to test the ability of the DHD to deliver a FIO2 of at least 0.85.

Method: Forty DHD were tested to assure uniform maximum flow capabilities using a Fisher-Porter calibration flowmeter (Bailey-Fischer & Porter, Warminster, Pennsylvania). Six randomly selected DHD were connected via the flowmeter to a simple mask with tubing. No fluid was applied to the DHD. A Laerdal intubation mannequin (Laerdal Medical Corp. Wappingers Falls, NY), served as a facial-interface. A Nellcor-Puritan Bennett 7820 Oxygen Monitor (Tyco Healthcare/Mallinckrodt, St.Louis, MO) was placed both at the DHD output and the trachea of the mannequin. Inspiratory demand was triggered by a connection of the mannequin’s trachea to one side of a two-compartment mechanical test lung (Michigan Instruments, Inc. Grand Rapids MI.). The test-lung was linked to the opposite test lung which was driven by a Puritan Bennett 7200 Series ventilator (Tyco Healthcare/Mallinckrodt, St.Louis, MO) in the continuous ventilation mode-volume controlled (CMV). CO2 was bled-in at a rate of 300 ml/min into the test lung to simulate physiological conditions. Each device was tested four times, once at each combination of frequencies (25 and 45/min) and tidal volumes (0.5 and 1.0 L). The driving flowmeter was connected to a 50 psig wall outlet and set at flush. FIO2 was measured by the inline oxygen analyzer placed within the mannequin trachea. The tracheal FIO2 for each device was measured at each frequency and tidal volume combination. The Repeated ANOVA, Paired T Test, and Spearman Rank Correlation were used to analyze results. Data were summarized as mean+/-SD.

Results: Mean maximum flow at of FIO2 of 0.95 for 40 nebulizers was 51.32 L/min with standard deviation of 2.11 L/min. The intratracheal FIO2 at minute ventilations (VE) 12.5, 22.5, 25, and 45 L/min respectively were 91.33+/-0.989, 88.28+/-1.15, 85.52+/-1.1, 70.47+/-0.54%. FIO2 at each VE differed statistically from FIO2 at the other 3 VE settings, p<0.001. Confidence intervals (95%) for VE of 22.5 and 25 L/min were 87.36 - 89.2% and 84.64-86.4%. FIO2 was negatively correlated with VE, r2=0.82, p<0.01.

Conclusions: The DHD high flow nebulizer provides consistent flows of 50 L/min at its highest FIO2 setting. It can deliver intratracheal FIO2 of at least 0.85 at 12.5 and 22.5 L/min VE, and failed to deliver FIO2 of 0.85 at VE 45 L/min. At VE 25 L/min, intratracheal FIO2 was statistically equivalent to 0.85. At highest flow demands, the DHD loses its ability to deliver high concentrations of intratracheal FIO2.

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