Abstract
Background:
Heated high flow nasal cannula (HHFNC) systems are increasingly used in the treatment of pediatric respiratory distress. Inline delivery of albuterol using a vibrating mesh nebulizer (VMN) is frequently used. Albuterol delivery during invasive and noninvasive ventilation is affected by circuit size. We hypothesize that using a larger circuit would allow higher drug delivery than a smaller circuit.
Methods:
We compared 2 different heated-wired circuits of same length but different internal diameters (13 vs. 22 mm) connected to a Fisher & Paykel Optiflow small adult cannula. A VMN was placed on the dry side of the humidifier, and the HHFNC was run at 5, 10, 15, and 20 L/min. Four units of the nebulizers loaded with 10 mg/4.5 mL of albuterol were tested. An anatomically correct pediatric model of a spontaneously breathing 5-year old child was used (tidal volume 200 mL, respiratory rate 20, inspiratory time 0.9s). Albuterol mass was measured via spectrophotometer, and reported as percentage of loading dose.
Results:
See table.
Conclusions:
Changing a circuit from small to large diameter has no effect on drug delivery with HHFNC at lower flows (5 and 10 L/min) but improves drug delivery at higher flows (15 and 20 L/min).
aExperiments were repeated and gave similar values View all access options for this article.Results
Flow (L/min)
5
10
15
20
Small circuit
12.1±1
7.5±0.1
4.8±0.3
2.8±0.5
Large circuit
10.1±1.8
8.2±0.4
11.7±1.1a
6.7±1
p value small vs. large
0.09
0.72
0.0006
0.001
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