Examining the Effects of Heliox to Drive Gas During High Frequency Jet Ventilation and Conventional Ventilation Tandem Use on a Test Lung Model

Abstract

Background:

Conventional ventilators (CV) can be powered by heliox (HeO₂) gas admixtures to provide clinicians with the ability to deliver mechanical breaths at reduced airway resistance, improved carbon dioxide diffusion, and decreased turbulent flows. High frequency jet ventilation (HFJV) is a time cycled pressure-limited ventilator used to provide less than dead space tidal volumes with transitional gas flows at high rapidity. The aim of this bench study was to discover what effects HeO₂ had on measured Servo pressure and tidal volume when used as a driving gas for HFJV and CV.

Methods:

A 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 MV (Getinge, Wayne, NJ). The test lung was attached to a 2.5 mm ETT, set to a resistance of 50 cm H₂O/L/s, rate of 42 breaths/min, 25% inspiratory time (0.36 s) with measured exhaled tidal volumes (Vte) of 9-10 mL while using CPAP +8 on MV. A LifePort ETT connected 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 were constant throughout the study. HFJV was powered by 50 PSI oxygen and a HeO₂ blender (Precision Medical, Northampton, PA) for the bench studies. A HeO₂ compensated Servo U was powered by 50 PSI air/O₂ gas supply and an H cylinder of HeO₂. Peak inspiratory pressure (PIP) on HFJV was increased to 20, 30, and 40 cm H₂O on room air, 80/20, 70/30, and 60/40 gas admixtures with HFJV alone, with CV alone, and simultaneously driven HeO₂. Dynamic compliance (Cdyn) and Vte were measured with the CV and Servo pressure was recorded on HFJV after achieving a 5-min steady state for changes to HFJV PIP and HeO₂ gas admixtures. Graphical representations of the data gathered were compiled to show the effects of HeO₂ on each device separately, combined, while using room air, and for the various HFJV PIP settings and HeO₂ gas admixtures.

Results:

HFJV driven HeO₂ had higher measured Vte and Cdyn when compared to CV driven HeO₂ on a lung model. The combination of HFJV and CV driven HeO₂ resulted in the highest measured Vte and Cdyn during the experiment.

Conclusions:

Data gathered during this experiment suggests that HFJV driven HeO₂ outperforms CV driven HeO₂. The direct impact of HeO₂ driven HFJV needs further study to decide the implications of its clinical or investigational research usage.

Measured Exhaled Tidal Volume

Dynamic Compliance