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.