Abstract
Background:
Heated high-flow nasal cannula (HHFNC) systems are used to treat children with hypoxemia and respiratory distress. These devices allow modification of flow and FIO2. We evaluated the effect of different FIO2 settings and the relationship between inspiratory and cannula flows on tracheal FIO2.
Methods:
An anatomically correct orotracheal model of a 5 y old child was connected to a breathing simulator (frequency = 20 breaths/minute, tidal 180 mL, TI 0.9 s, inspiratory flow 12 L/min), and an oxygen analyzer was interposed. A Fisher Paykel (FP) Optiflow Junior 2 XL cannula was used with the Fisher Paykel HHFNC system with a blender and the AIRVO 2 device with cannula flows of 6, and 12 L/min. Another oxygen analyzer was placed in-line with the circuit at the cannula connection. FIO2 was set at 0.95, 0.70, 0.50 and 0.35. Circuit and tracheal FIO2 was measured. Absolute difference between device and tracheal FIO2 (Delta FIO2) at different FIO2 s, and Delta FIO2 at 6 and 12 L/min were analyzed. Measurements were done in quadruplicate after 7 minutes of continuous operation.
Results:
See table.
Conclusions:
Delta FIO2 was greater at higher FIO2 settings. The effect of air entrainment was more evident at higher FIO2 settings. The AIRVO 2 device was more effective than the FP device when cannula flow matched inspiratory flow.
*6 is > 12 L/min. # AIRVO < FP. View all access options for this article.Delta FIO2 expressed in absolute % points, X ± SD
Flow
6 L/min
12 L/min
FI02
FP
AIRVO 2
FP
AIRVO 2
0.95
-36 ± 6*
-30 ± 1*
-12 ± 4
-3 ± 3#
0.70
-14 ± 4
-17 ± 5*
-9 ± 1
4 ± 1#
0.50
-9 ± 2
-9 ± 2*
-6 ± 0
2 ± 0#
0.35
-3 ± 2
-3 ± 1
-2 ± 4
-3 ± 3
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