Heliox delivery with noninvasive positive pressure ventilation: a laboratory study.

Area of Science:

• Respiratory therapy
• Biomedical engineering
• Gas dynamics

Background:

• Clinical interest exists in using heliox (helium-oxygen mixture) with noninvasive positive pressure ventilation (NPPV).
• Previous reports on delivering heliox with NPPV ventilators are lacking.
• This study evaluates helium concentration ([He]) using heliox with five different NPPV ventilators.

Purpose of the Study:

• To determine the factors affecting helium concentration ([He]) when using heliox with NPPV ventilators.
• To assess the performance and potential malfunctions of NPPV ventilators when delivering heliox.
• To investigate the impact of heliox on positive airway pressure during NPPV.

Main Methods:

• Five NPPV ventilators were tested using a simulated lung model with a standard leak.
• Heliox and oxygen flows were titrated at proximal and distal positions.
• The BiPAP Vision ventilator was also tested using a blender method.
• Ventilators operated in spontaneous/timed mode across various pressure settings.

Main Results:

• Heliox flow, NPPV settings, infusion site, and ventilator type significantly impacted [He].
• Heliox concentrations exceeding 60% were achieved with 18 L/min heliox flow under specific conditions.
• Some ventilators (BiPAP S/T-D30, Quantum, BiPAP Vision) exhibited erratic function.
• Positive airway pressure remained largely unaffected when ventilators functioned correctly.

Conclusions:

• Heliox flow rate is the primary determinant of [He] during NPPV.
• Potential for ventilator malfunction exists when using heliox with NPPV.
• Clinical implications of these findings require further investigation.