Anaesthesia and intensive care
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Recent modes of ventilatory support aim to facilitate weaning and minimise the physiological disadvantages of intermittent positive pressure ventilation (IPPV). Intermittent mandatory ventilation (IMV) allows the patient to breathe spontaneously in between ventilator breaths. ⋯ Other modes or refinements of IPPV include high frequency ventilation, expiratory retard, differential lung ventilation, inversed ratio ventilation, 'sighs', varied inspiratory flow waveforms and extracorporeal membrane oxygenation. While these techniques have useful applications in selective situations, IPPV remains the mainstay of managing respiratory failure for most patients.
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Over the last six years high-frequency ventilation has been extensively evaluated both in the clinical and laboratory settings. It is now no longer the great mystery it once was, and it is now no longer believed (as many had hoped), that it will solve all the problems associated with mechanical pulmonary ventilation. Although the technique is safe and appears to cause no harm even in the long term, it has not yet been shown to offer any major advantages over conventional mechanical ventilation.
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This paper reviews the state of the art in Australia of manually operated, self-inflating bag resuscitators, including the Laerdal, Air Viva and Ambu; manually operated bags dependent upon an oxygen supply, including Mapleson B, C, E and F, the CIG Medishield Oxy-Saver and modified Oxy-Viva Resuscitator 3, and the Komesaroff Oxy-Resuscitator RD85; oxygen-powered resuscitators, including the Oxy-Viva Resuscitator 3 with Demand and RM2 Valves, and the Oxylife FM85; and portable ventilators, including the Drager Oxylog, and Ohmeda Logic 07. Specific comment is made to the effect that the design of the resuscitator is often less important than the knowledge and ability of the operator in using the equipment to achieve adequate lung ventilation. ⋯ With special training, use of more complex equipment can be justified in some circumstances. The more complex the equipment, the greater the risk of inappropriate use, and the greater the risk of equipment malfunction unless a regular maintenance program is followed.