Bench Evaluation of the Impact of Heliox on High Frequency Jet Ventilation and Conventional Ventilation Measured Parameters Using a Test Lung Model

Abstract

Background: Heliox is a low density gas that enhances aerosol drug delivery, increases laminar flow, and improves carbon dioxide diffusion. High frequency jet ventilation (HFJV) is a time-cycled pressure limited ventilator that delivers less than dead space tidal volumes with transitional gas flows at high celerity. The purpose of this study was to evaluate whether heliox at any admixture affected MAP and Servo pressure on the HFJV.

Methods: The QuickLung Breather (IngMar Medical, Pittsburgh, PA) test lung model was used to simulate spontaneous respirations while connected to a LifePulse HFJV (Salt Lake City, UT) and a Servo-U conventional ventilator (CV) (Getinge, Wayne, NJ). The test lung was attached to a 2.5 mm ETT set to a resistance of 50 cm H₂0 /L/S, frequency 42 breaths/min, 25% inspiratory time (0.36 s), with measured exhaled tidal volumes of 9-10 mL while using CPAP +8 on CV. A LifePort ETT connected the HFJV and CV circuit to the ETT and lung model. A jet rate of 300 breaths/min and I-time 0.02 s, and CPAP +8 (CV) were constant throughout the study. HFJV was powered by wall sourced, 50 PSI oxygen and then added a heliox blender (Precision Medical (Northampton, PA.) for the test separately. Peak inspiratory pressure (PIP) on HFJV was increased to 20, 30, and 40 cm H₂O on room air, and 80/20, heliox gas admixture upon achieving a 5-min steady state for changes in PIP and heliox concentration exhaled tidal volumes (CV) and Servo pressure, MAP (HFJV) was recorded. Mean and standard deviations of combined HFJV + CV on room air vs 80/20 heliox powered to the CV and the HFJV were calculated and compared using a t-test with a statistical significance level set at P < .05.

Results: There was a statistically significant difference in MAP (P = .035) with changes in heliox compared to room air. In the presence of heliox, neither Servo pressure nor MAP were different.

Conclusions: Tidal volume increases as a heliox gas admixture is added to HFJV. Future applications and testing with different Heliox concentrations needs to be studied further.