Anaesthesia and intensive care
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Anaesth Intensive Care · Jun 1995
Comparative StudyMaxima and Bain breathing systems compared in controlled ventilation.
The Maxima is a new universal breathing system, which, despite its being valveless, functions with near maximal efficiency in spontaneous and controlled ventilation. It was compared to the Bain system in controlled ventilation by adjusting fresh gas flows (VF) to achieve an end-tidal CO2 of 5% in 40 patients aged from one to seventy-six years. They received a combined regional and general anaesthetic technique. ⋯ The mean VF requirement for the Bain system was greater by 45%. Of these forty patients, the results from the twenty-four adult patients weighing 50 kg or more gave the respective VF requirements for the Maxima and Bain systems of 52 and 71 ml.min-1.kg-1. In a separate study using twenty-nine patients, the fractional utilization of fresh gas (FU) (or VAe/VF where VAe = effective alveolar ventilation) in the Maxima and Bain systems was shown to be 0.94 and 0.71 respectively.
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Anaesth Intensive Care · Jun 1995
Comparative StudyA comparative evaluation of pressure-triggering and flow-triggering in pressure support ventilation (PSV) for neonates using an animal model.
The triggering system in pressure support ventilation needs to respond rapidly, especially in neonates. The aim of this study was to compare the effects of flow-triggered and pressure-triggered pressure support ventilation on neonatal mechanical ventilation using an animal model. Respiratory flow, airway pressure, oesophageal pressure, and diaphragmatic electromyogram were measured during pressure support ventilation in five anaesthetized rabbits. ⋯ Shorter trigger delay and longer pressure support time were observed in flow-triggering. There was also less diaphragmatic activity in flow-triggering as evidenced by the amplitude of integrated diaphragmatic electromyogram and negative deflection of oesophageal pressure. The findings suggest that flow-triggering will prove superior to pressure-triggering in pressure support ventilation for neonates.