Research

High flow biphasic positive airway pressure by helmet – effects on pressurization, tidal volume, carbon dioxide accumulation and noise exposure

Onnen Moerer¹ , Peter Herrmann¹ , José Hinz¹ , Paolo Severgnini² , Edoardo Calderini³ , Michael Quintel¹ and Paolo Pelosi²

¹Department of Anaesthesiology, Emergency and Critical Care Medicine, University of Göttingen, Robert-Koch-Strasse 40, 37075 Göttingen, Germany

²Dipartimento di Anestesia, Rianimazione e Terapia del Dolore, Fondazione Ospedale Maggiore Policlinico, Mangiagalli e Regina Elena, IRCCS, via Francesco Sforza 28, 20122 Milano, Italy

³Department of Ambient, Health and Safety, c/o Villa Toeplitz Via G.B. Vico, 46, 21100 Varese, Italy

author email corresponding author email

Critical Care 2009, 13:R85doi:10.1186/cc7907

Published:	5 June 2009

Abstract

Introduction

Non-invasive ventilation (NIV) with a helmet device is often associated with poor patient-ventilator synchrony and impaired carbon dioxide (CO₂) removal, which might lead to failure. A possible solution is to use a high free flow system in combination with a time-cycled pressure valve placed into the expiratory circuit (HF-BiPAP). This system would be independent from triggering while providing a high flow to eliminate CO₂.

Methods

Conventional pressure support ventilation (PSV) and time-cycled biphasic pressure controlled ventilation (BiVent) delivered by an Intensive Care Unit ventilator were compared to HF-BiPAP in an in vitro lung model study. Variables included delta pressures of 5 and 15 cmH2O, respiratory rates of 15 and 30 breaths/min, inspiratory efforts (respiratory drive) of 2.5 and 10 cmH2O) and different lung characteristics. Additionally, CO₂ removal and noise exposure were measured.

Results

Pressurization during inspiration was more effective with pressure controlled modes compared to PSV (P < 0.001) at similar tidal volumes. During the expiratory phase, BiVent and HF-BiPAP led to an increase in pressure burden compared to PSV. This was especially true at higher upper pressures (P < 0.001). At high level of asynchrony both HF-BiPAP and BiVent were less effective. Only HF-BiPAP ventilation effectively removed CO2 (P < 0.001) during all settings. Noise exposure was higher during HF-BiPAP (P < 0.001).

Conclusions

This study demonstrates that in a lung model, the efficiency of NIV by helmet can be improved by using HF-BiPAP. However, it imposes a higher pressure during the expiratory phase. CO2 was almost completely removed with HF-BiPAP during all settings.