Abstract
IntroductionNon-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.MethodsConventional 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.ResultsPressurization 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).ConclusionsThis 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.
Highlights
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
biphasic pressure ventilation (BiVent) and HF-BiPAP led to an increase in pressure burden compared to pressure ventilation (PSV)
There was no significant difference between the tested modes regarding the mean Δ pressure at low (PSV: 5.3 ± 0.4 cmH2O, BiVent: 5.4 ± 0.6 cmH2O, HF-BiPAP: 5.3 ± 0.9 cmH2O; P = 0.119) and high upper pressure (PSV: 15.2 ± 0.7 cmH2O, BiVent: 15 ± 1 cmH2O, HF-BiPAP; 15.1 ± 2.4 cmH2O; P = 0.308)
Summary
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). Problems with the commonly used interfaces of the NIV application include air leakage [8,9], patient discomfort [10], and pressure-related ulcerations of the nose [11] All of these problems can limit the duration of NIV and account for failures [12]. Due to the large collapsible and compliant chamber that encompasses the patient's head, the ANOVA: analysis of variance; BiVent: time-cycled pressure controlled switching between two continuous positive airway pressure levels; CO2: carbon dioxide; CPAP: continuous positive airway pressure; HF-BiPAP: high flow biphasic positive airway pressure; NIV: non-invasive ventilation; PEEP: positive end-expiratory pressure; PSV: pressure support ventilation; PTP: pressure time product
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