Anaesthesia and intensive care
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Breathing through an endotracheal tube, connector, and ventilator demand valve imposes an added load on the respiratory muscles. As respiratory muscle fatigue is thought to be a frequent cause of ventilator dependence, we sought to examine the efficacy of five different ventilators in reducing this imposed work through the application of pressure support ventilation. Using a model of spontaneous breathing, we examined the apparatus work imposed by the Servo 900-C, Puritan Bennett 7200a, Engstrom Erica, Drager EV-A or Hamilton Veolar ventilators, a size 7.0 and 8.0 mm endotracheal tube, and inspiratory flow rates of 40 and 60 l/min. ⋯ However, the maximum negative pressure was greater for the Servo 900-C. The added work of breathing through endotracheal tubes and ventilator demand valves may be compensated for by the application of pressure support. The level of pressure support required depends on inspiratory flow rate, endotracheal tube size, and type of ventilator.
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Anaesth Intensive Care · Feb 1993
Insertion of the laryngeal mask airway--a prospective study of four techniques.
The standard insertion technique (ST 0) for laryngeal mask airway insertion was compared to three alternative techniques in 120 patients. The alternative techniques included insertion using the standard approach, but with the cuff either semi-inflated (ST 0.5) or fully inflated (ST 1.0), and a non-standard approach using a back-to-front technique (like a Guedel airway) and with the cuff fully deflated (T 180). ⋯ Insertion with the LMA back-to-front with the cuff deflated produced similar fibreoptic and functional results to the standard technique. In 23%, however, there was some residual rotation of 25-90% to the coronal plane.