A Bench Evaluation of CO2 Retention With Intrapulmonary Percussive Ventilation in a Neonatal Circuit and Neonatal Lung Model

Abstract

Background:

For years there has been a belief that the Percussionaire Turbohub delivers rebreathed CO₂ to patients. Primary Children’s Hospital uses the VDR with Turbohub in our NICU and PICU, so we wondered just how much CO₂ was being rebreathed and if there was a way to eliminate it.

Methods:

The Percussionaire VDR with Turbohub was set up with an F&P Evaqua 2 infant ventilator circuit and attached to a 0.59 cc/cm H₂O compliant ridged test lung. CO₂ analyzers from the Drager Evita XL were attached at the test lung to read exhaled CO₂, and at the inspiratory side of the Turbohub to measure the amount of CO₂ being rebreathed. CO₂ was injected into the test lung via blended air/CO₂ mixture at 0.3 L/min to achieve an ETCO2 of approximately 35 torr. O₂ tubing for external flow was attached to the inspiratory relief valve on the Turbohub and to a flow meter. External flows up to 6 L/min were used during testing. The VDR was set at a working pressure of 40 psi, 1 second convective rate I time and high frequency I:E ratio at 1:1. Various peak pressures, peeps as well as some different convective rates and percussive rates were used to see how much CO₂ was rebreathed at each setting and if it changed using different settings. CO₂ measurements were obtained after settings had 5 minutes to stabilize. External flow ranging from 1 to 6 L/min was added at each setting after initial measurements were taken, and CO₂ was measured again.

Results:

Thru all ranges of settings rebreathed CO₂ was 3 to 6t orr without added external flow. Upon adding external flow to the Turbohub the CO₂ gradually decreased until it reached 0 at 6 L/min of flow in all test settings.

Conclusions:

According to the data collected, it appears that patients do in fact rebreathe CO₂ on the VDR with Turbohub. Adding 6 L/min of flow to the inspiratory side of the Turbohub would likely be beneficial to eliminating CO₂. We also found that adding the additional flow required us to decrease the pulsatile flow and oscillatory CPAP/PEEP to maintain the PIP and PEEP test setting. Further testing may be indicated to change clinical practice.