Anaesthesia and intensive care
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Anaesth Intensive Care · Jun 1995
Detection of cerebral venous desaturation by continuous jugular bulb oximetry following acute neurotrauma.
A prospective observational study was performed to assess the reliability of fibreoptic oximetric catheters and to identify the incidence and causes of jugular bulb oxygen desaturation in patients with acute closed head injury. There were twenty-five patients (30 +/- 16 years) with GCS < or = 8 in this study. Jugular bulb oximetry, mean arterial pressure, intracranial pressure, end-tidal CO2 and pulse oximetry were monitored continuously. ⋯ Validation with a laboratory oximeter is essential prior to continuous jugular bulb oximetry. Sustained episodes of cerebral venous desaturation are frequent within the first 48 hours following acute head injury. Factors such as hypocapnia and cerebral hypoperfusion that primarily reduce cerebral blood flow are predominant.
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Anaesth Intensive Care · Jun 1995
Comparative StudyComparison in spontaneous ventilation of the Maxima with the Humphrey ADE breathing system and between four methods for detecting rebreathing.
An enclosed efferent, afferent reservoir breathing system (Maxima, Life Air Pty Ltd), being valveless, was compared to a simple afferent reservoir system (Humphrey ADE, A mode), having a valve, by assessing fresh gas flow (VF) requirements, with respect to ventilation (VE), that prevents rebreathing in volunteers, awake and breathing spontaneously. The results are recorded in terms of the quotient VF/VE associated with the onset of rebreathing. ⋯ Our findings showed that the method of sampling carbon dioxide (CO2) at the outflow of the efferent limb of the patient connector (eliminated CO2 method) in both afferent reservoir systems provided the highest flow rate and most reliable indication for detecting potential or actual rebreathing, when attempting to minimize VF. It provides no additional deadspace or resistance to gas flow, and has the advantage of being the only qualitative method that is reliable for the purpose of detecting the onset of rebreathing.
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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.