Anaesthesia
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Comparative Study
A nasal CPAP system. Description and comparison with facemask CPAP.
Nasopharyngeal pressures were compared in eight subjects breathing through either a nasal CPAP system or facemask CPAP system at a fresh gas flow of 50, 75 and 100 l.min-1. During nose breathing there was no significant difference in nasopharyngeal pressure between the two systems. ⋯ During nose breathing at 75 l.min-1 the mean inspiratory and expiratory pressures in cmH2O (SD) were 3.4 (0.68) and 5.9 (0.55) for nasal CPAP and 3.3 (0.71) and 6.3 (0.73) for facemask CPAP. The respective pressures during mouth breathing were 0.3 (0.73) and 2.9 (1.74) for nasal CPAP and 3.9 (0.73) and 5.8 (0.82) for facemask CPAP.
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Comparative Study
Cardiovascular responses to insertion of the laryngeal mask.
We have compared, in 40 healthy patients, the cardiovascular responses induced by laryngoscopy and intubation with those produced by insertion of a laryngeal mask. Anaesthesia was induced with thiopentone and maintained with enflurane and nitrous oxide in oxygen; vecuronium was used for muscle relaxation. ⋯ Increases in maximum heart rate were similar, (26.6% v 25.7%) although heart rate remained elevated for longer after tracheal intubation. We conclude that insertion of the laryngeal mask airway is accompanied by smaller cardiovascular responses than those after laryngoscopy and intubation and that its use may be indicated in those patients in whom a marked pressor response would be deleterious.
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Comparative Study
Resistance and additional inspiratory work imposed by the laryngeal mask airway. A comparison with tracheal tubes.
Laryngeal mask airways and tracheal tubes were studied to determine both their resistance to constant gas flows and additional inspiratory work during simulated inspiration. Laryngeal mask airways imposed less resistance and required lower additional inspiratory work compared with the corresponding sized tracheal tubes. If inspiratory loading during anaesthesia is an important consideration, then the laryngeal mask airway may be preferable to a tracheal tube.