Articles: intubation.
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Pressure-flow relationships of an artificial airway-mechanical ventilator system were investigated. Endotracheal tubes varying from 7 to 9.5 mm. internal diameter and tracheostomy tubes from 7 to 10 mm. internal diameter were tested over flow-rates from 0.3 to 1.4 L. per second using a tidal volume of 500 ml. The effect of partial obstruction within these airways by suction catheters and the bronchofiberscope was examined. ⋯ H2O and reduced the flow rate to 50 per cent and the tidal volume to 80 per cent of its set value. Attention should be paid to duration of tracheobronchial suction while the patient is removed from the respirator since a high-grade resistance is created by passage of a suction catheter through an endotracheal tube. Bronchofiberscopy should be cautiously performed through cuffed artificial airways with at least 8 mm. internal diameter because the airway may be too comprised even if mechanical ventilatory assistance is employed.
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Comparative Study
A study of inflatable cuffs on endotracheal tubes. Pressures exerted on the trachea.
A simple method of measuring the pressure exerted by the cuff of an endotracheal tube on the trachea is described and has been used to measure the pressures exerted by 16 commercially available cuffs on the wall of a model trachea. The Shiley, Portex soft-seal, Kamen-Wilkinson (Bivona Fome) tubes had the lowest tracheal wall pressures. Using this method in vivo the changes in tracheal wall pressure exerted by a low-pressure cuff during percussion and vibration physiotherapy, and when the patient "fights the ventilator", were recorded.
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The authors present six cases of difficult intubation and review the literature on this subject; The circumstances during which difficult intubation may be feared are recalled; some are due to the morphology of the subject, the others to his previous pathology which may be rheumatological or dermatological. The authors then discuss the method of anaesthesia for this unusual intubation and the various technical means proposed to carry out safely the intubation itself.