CPAP Delivery via Next Generation Nasal Cannula and Prong Interfaces in an Infant Model

Abstract

Background:

Nasal CPAP is an established method to provide NIV support to spontaneously breathing infants. In infants, CPAP is commonly applied using bi-nasal short prongs. Recently, there has been increased interest in the use of next generation nasal cannulas, such as RAM cannula (Neotech), to delivery CPAP. However, due to inherent resistance concerns, some centers have reported the use Optiflow cannulas (Fisher & Paykel) as an alternative. The aim of this study was to quantify CPAP delivery through RAM and Optiflow cannulas and bi-nasal short prongs in a simulated infant lung model.

Methods:

An infant manikin (AirSim Baby X, TruCorp), with an anatomically correct airway of a 6-month-old, was connected to a breathing simulator (ASL 5000, Ingmar Medical) with parameters set to simulate a 6-month-old weighing approximately 7 kg (36 breaths/min, Ti of 0.45 s, R of 40 cm H₂O/L/s, C of 10 mL/cm H₂O, and V_T of 43 mL). CPAP of 5 was provided by a Servo-i ventilator (Maquet) in nCPAP mode and delivered through four cannulas; RAM (N4903 Orange, N4904 Yellow) & Optiflow (OJR418 Jr XL, OPT942 SML Adult), and one size Fisher & Paykel (5040) bi-nasal short prong. Sizes were chosen to represent approximately 80-90% nares occlusion. The Jr XL and RAM cannulas bifurcate into two small tubes that supply gas flow to nasal cannula prongs, while the SML Adult cannula has a single larger tube. Simulations were performed with mouth closed. Outcome measures were MAP compared to set CPAP and ΔP_aw (difference between mean expiratory and inspiratory pressure). Data was collected over 36 breaths. Descriptive statistics are presented as mean values only and one-way ANOVA with Holm-Sidak method used for multiple comparison.

Results:

The bi-nasal short prongs delivered 96% of set CPAP (4.8 cm H₂O), significantly more than all tested cannulas and produced the least amount of ΔP_aw (1.4 cm H₂O) (P < .05). At similar occlusions, the SML Adult Optiflow cannula delivered 91% of set CPAP (4.5 cm H₂O) vs 75% (3.8 cm H₂O) with the RAM Yellow and had less ΔP_aw (2.0 vs 2.4 cm H₂O) (P < .05). At 80% occlusion, the Optiflow Jr XL and RAM Orange delivered 36% and 18% of set CPAP respectively, and the RAM Orange failed to maintain positive pressure during inhalation (Table 1).

Conclusions:

The SML Adult Optiflow cannula and bi-nasal short prongs delivered > 90% of set CPAP level at similar nares occlusion. Cannula design and nares occlusion affect pressure transmission.