Abstract
Background:
Flexi trunk and RAM Cannula are common interfaces used with Bubble CPAP to provide positive airway pressure (PAP) respiratory support in the neonatal intensive care unit. Local neonatal providers anecdotally noted that subjects treated with flexi trunk have demonstrated consistent goal of PAP therapy vs the use of RAM Cannula. This study looked at potential differences in delivered pressure and flow from the sized-paired devices.
Methods:
This bench study measured pressure and flow using the RAM Cannula (Neotech) and Flexi Trunk (Fisher & Paykel) delivered to a simulated infant head (Michigan Instruments). Both interfaces were connected to a Bubble CPAP System (Fisher & Paykel) with pressure set at 5 and 8 cm H2O and continuous flow set at 10 L/min. The Mallinckrodt Puritan-Bennett PTS 2000 Ventilator Tester was used to measure the pressure and flow, once stabilized, via ports downstream from the simulated nares of the infant model head. Three sizes of Neotech RAM Cannula were used (3mm, 3.5 mm, and 4mm). Three Infant Nasal Prongs BC3020-10, BC3520-10, and BC4030-10 (Fisher & Paykel) were connected to Different sizes Flexi Trunk Midline Interfaces 50mm, 70 mm, and 100mm. Reported Flexi Trunk data is average of all readings for respective prong size. All interfaces were attached to the model head in fashion like patient care. All other openings, within simulated head, were occluded to prevent leak during measurements. IBM SPSS software was used for t-test analysis and significance is set at P <.05.
Results:
The chart below describes the flow and pressure measured with the size-paired interfaces. In many cases, Flexi trunk device delivered more pressure and, in every test, delivered flow was higher than the similar sized RAM cannula.
Conclusions:
In this study with a single simulated head, there were significant differences in delivered pressure and flow between the sized-paired RAM Cannula and Flexi Trunk interfaces. This study cannot infer that one interface is more effective than another device in neonatal subjects. Further research should include in vivo study to compare the interfaces’ performance.
RAM Cannula Versus Flexi Trunk
pressure setting 10L/min set
Prong size
RAM Cannula mean (cmH2O)
Flexi Trunk mean (cmh2O)
p value
5 CPAP
3 mm
2.6
2.03
0.0002*
5 CPAP
3.5 mm
5.4
5.8
0.2021
5 CPAP
4 mm
5.5
6.13
0.0009*
8 CPAP
3 mm
3.56
3.01
0.001*
8 CPAP
3.5 mm
7.7
8.33
0.002*
8 CPAP
4 mm
8
8.33
0.1756
Flow setting 10 L/min
Prong size
RAM Cannula mean (L/min)
Flexi Trunk mean (L/min)
p value
5 CPAP
3 mm
4.14
4.59
0.001*
5 CPAP
3.5 mm
4.87
7.29
0.0003*
5 CPAP
4 mm
5.56
9.83
0.001*
8 CPAP
3 mm
5.2
5.61
0.0011*
8 CPAP
3.5 mm
6.4
9.64
0.001*
8 CPAP
4 mm
7.4
9.86
0.001*
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