Summary Surcej.s conducted in the United

A theoretical analysis has been performed to show the interrelationships between alveolar carbon dioxide concentration, carbon dioxide output, alveolar ventilation and fresh gas flow during controlled ventilation with the Mapleson D system. The model and forms of equation used have been substantiated by experiments in which dogs were ventilated through a coaxial version of the Mapleson D system at varying levels of fresh gas flow and alveolar ventilation. By assuming that man ventilated with this system behaves as does the dog, a nomogram has been produced to predict alveolar carbon dioxide concentrations at any levels of fresh gas flow and minute volume.

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SummaryThe accuracy of the Nellcor N-101 pulse oximeter has been evaluated in adult patients receiving general anaesthesia or intensive care. Readings obtained noninvasively with this instrument were compared with measurements made on arterial blood using a Radiometer OSM2 oximeter. The pulse oximeter was easy to use and within the range tested (70-100percent saturation of haemoglobin with oxygen) the readings were uithin I digit of the values obtained by in vitro measurement.

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