Anaesthesia
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Historical Article
The development of apparatus for intermittent negative pressure respiration. (2) 1919-1976, with special reference to the development and uses of cuirass respirators.
This paper and the one that preceded it1 have traced the development of the design and use of negative pressure ventilators from their origins in the early nineteenth century to the present day. Their maximum use was in the nineteen-forties and the early fifties after which they were quite rapidly replaced in the treatment of acute respiratory disease by intermittent positive pressure ventilators-the turning point being the severe poliomyelitis epidemic in Copenhagen in 1952. Negative pressure ventilators, particularly cuirass ventilators, still have a place in the treatment of chronic respiratory disease.
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Intracranial pressure changes were observed in 10 children with hydrocephalus after ketamine administration. Three patients showed an elevation of pressure and a fall was observed in 7 patients. Two more patients who were given ketamine while under general anaesthesia and IPPV also showed a fall in pressure. No explanation is forthcoming at present for such an unusual response, but an altered cerebral vascular response in the presence of promethazine and general anaesthesia has been postulated.
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Comparative Study
Venous air embolism during neurosurgery. A comparison of various methods of detection in man.
A comparison of the various methods available for the detection of air embolus has been carried out in patients undergoing posterior fossa exploration in the sitting position. A group of 17 patients (Group A) was comprehensively monitored by a central venous catheter, an infra-red carbon dioxide analyser and a Doppler ultrasonic flow transducer in addition to more traditional clinical methods. Group B (19 patients) was monitored by commonly used clinical methods consisting of continuous palpation of the radial pulse, intermittent blood pressure measurement, the use of an oesophageal stethoscope and the electrocardiograph. ⋯ In Group B air embolus was diagnosed in 10% of patients. One patient in each group died from air embolus; one patient had a paradoxical embolus to the coronary arteries. It is concluded that comprehensive monitoring for air embolus, including the use of Doppler ultrasound, is an essential part of the management of these patients, for both diagnosis and treatment.