Abstract
Background: Noninvasive ventilation (NIV) is a commonly used mode of ventilation to provide respiratory support after planned extubation of the neonate. Further investigation of the various interfaces and ventilators utilized to administer NIV is needed in order to optimize the support delivered to the infant. Some centers use the NeoTech RAM Cannula as the interface for delivery of NIV in conjunction with several different ventilators. This ex vivo experimental design evaluated the PIP, PEEP, and MAP delivered during NIV with the Vyasis Avea (Avea) ventilator in conjunction with three sizes of RAM Cannula using the IngMar Medical ASL 5000 electronic lung simulator (ASL 5000). Methods: The simulator was programmed to model a neonate (1-3kg body weight) with normal to moderately affected lungs. ASL 5000 settings: Cst 1.5 mL/cm H2O, Raw 70 cm H2O/L/s, Pmus Maximum, f zero (passive model). A 3D printed interface was created for each size RAM cannula (outer prong sizes: 3.5, 3.0 and 3.0 mm) with openings approximately 20% larger than the outer dimensions of the RAM prongs; the interface connected directly to the neonatal adapter on the ASL 5000. Simulated nares sizes were: Micro Preemie 3.6 cm, Preemie 3.6 cm, Neonate 4.2 cm. The EST was completed on the Avea, and the interface calibration was completed for each size RAM prior to testing. Each size cannula was then evaluated in Nasal CPAP/IMV mode at the following settings: 1) rate 20 breaths/min, 2) inspiratory time 0.25, 0.30 and 0.35 seconds, 3) PIP 10, 20 and 30 cm H2O, 4) rise of 9, 5) PEEP 5, 8 and 10 cm H2O, 6) FIO2 at 0.21. The ASL 5000 recorded data, including the delivered PIP, PEEP and MAP, for one minute at each combination of settings, and each size RAM Cannula. Results: The delivered PIP, as measured by the ASL 5000, approximated the set value on the ventilator only when the set PIP was 10 cm H2O. The data show that the PEEP recorded from the ASL 5000 was consistently lower than the PEEP level set on the Avea. With an increase in inspiratory time, there was a slight increase in both delivered PIP and PEEP. The delivered PIP and PEEP decreased as the RAM Cannula was sized down. Conclusions: When properly sized to the nasal diameter, the NeoTech RAM Cannula interface results in the delivery of lower pressures than set on the Avea. Based on the results of this bench study, pressure attenuation to lower than set pressure is likely when utilizing the RAM Cannula for NIV with the Avea.
Footnotes
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