Comparison of Noninvasive Ventilation Delivered by Nasal Prongs in a High Fidelity Mannikin

Abstract

Background:

RAM cannula proper fit is 60-80% occlusion of the nares. Our goal was to see how different size RAM cannulas and nasal prongs compare on a high fidelity mannikin, utilizing simulated lung pressure monitoring. If the leak around the prongs or cannula is too large, there would be ineffective transfer of pressure from the ventilator to the simulation lungs. Therefore, the ventilator could possibly deliver enough flow to create back pressure at the interface to achieve its desired pressure.

Methods:

A Servo-i Ventilator was used in non-invasive PCV mode thru multiple interfaces on Gaumard's Super Tory model S2220 mannikin. The setting used was NIV PCV with a set RR 24, PIP 17cm H₂O, PEEP of +5 cm H₂O and Ti 0.5 s. The mannikin was intubated with a 3.0 cuffed endotracheal tube to get baseline data. After gathering the data, the mannikin was extubated. The mouth was then closed using a chin strap. The anterior portion of the nares measured at 4.2 mm in diameter. Data was collected from Servo-i's measured values as well as Super Tory's lung pressure using Fisher & Paykel prong sizes 3520 (outer diameter 3.5 mm) and 4030 (outer diameter 4.0 mm). The same was done using the RAM cannula sizes: micro preemie (outer diameter 3.0 mm), preemie (outer diameter 3.0 mm) and newborn (outer diameter 3.5 mm).

Results:

The cuffed endotracheal tube showed translation of pressure from the Servo-i to the Super Tory's lungs. The 4030 prongs, occluding 95% of the nares, maintained the desired PIP and PEEP, with a ventilator-detected leak of 29%. The 3520 prongs, which occluded 83% of the mannikin's nares, delivered pressures close to the set PIP (94% of desired) and PEEP (80% of desired) with a ventilator leak of 64%. The RAM cannula newborn size, which occluded 83% of the nares, delivered 88% of set PIP and 80% of set PEEP with a ventilator leak of 61%. The preemie size, which occluded 71% of the nares, delivered set PIP (between 23-70% of desired) and PEEP (0% of desired), with ventilator leak of 78%. The micro preemie size occluded 71% of the nares, but had a shorter nasal-septal distance and poor fit, therefore unable to deliver any detectable PIP or PEEP to the simulation lungs.

Conclusions:

The Servo-i did not see a drop in measured PIP, PEEP or volumes delivered that would alert caregivers of ineffective support with any interface used.60-80% occlusion of nares with RAM cannula in simulation mannikin did not translate adequate pressure to lungs.

Interface used	Vent PIP	Vent PEEP	Vti	Vte	Servo-i leak%	Vent MV	Tory	Tory	Chest rise
3.0 ET tube cuffed	17cm H2O	5cm H2O	21ml	21ml	1%	0.6L/M	18cm H2O	5cm H2O	yes
4030 F&P prongs	17cm H2O	5cm H2O	26ml	25ml	29%	0.6L/M	18cm H2O	5cm H2O	yes
3520 F&P prongs	17cm H2O	5cm H2O	27ml	25ml	64%	0.6L/M	16cm H2O	4cm H2O	minimal rise
RAM Newborn	17cm H2O	5cm H2O	26ml	23ml	61%	0.6L/M	15cm H2O	4cm H2O	minimal rise
RAM Premie	16cm H2O	5cm H2O	23ml	20ml	78%	0.5M/L	4-12cm H2O	0cm H2O	none
RAM Micro Premie	16cm H2O	5cm H2O	17.9ml	16.5ml	89%	0.36L/M	0cm H2O	0cm H2O	none