Biomedical subjects
B G Dodgson
Publications and source records attributed to B G Dodgson.
Inappropriate use of the oxygen flush to check an anaesthetic machine.
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Chemical regulation of ventilation during isoflurane sedation and anaesthesia in humans.
To assess the effects of isoflurane on chemical regulation of ventilation, we studied the ventilatory responses to (1) hyperoxic hypercarbia, (2) isocapnic hypoxaemia, and (3) a single half vital capacity breath of carbon dioxide 20 per cent in oxygen in 12 human subjects, awake and sedated or anaesthetized with isoflurane, 0.1 or 1.1 MAC. Sedation did not alter ventilation nor the ventilatory response to hypercarbia but reduced the responses to hypoxaemia and to the half vital capacity breath of CO2. Anaesthesia reduced ventilation and the response to hypercarbia and nearly abolished the responses to hypoxaemia and to the breath of CO2. The results indicate that isoflurane reduces ventilatory responses to several chemical drives and that it selectively impairs those responses mediated by peripheral chemoreceptors. In these respects, isoflurane is similar to halothane and enflurane.
Assessment of two noninvasive monitors of arterial oxygenation in anesthetized man.
The Hewlett-Packard 47201A ear oximeter and the Radiometer TCM1 transcutaneous oxygen monitor were evaluated for use as noninvasive monitors of arterial oxygenation during inhalational anesthesia in man. Thirty-four healthy adult volunteers were anesthetized to steady states with halothane, enflurane, or isoflurane, and were studied either before or during surgery. Oxygen levels were varied over ranges that included hypoxemia, by manipulating FIO2. Oximeter estimates of SaO2 values and transcutaneous estimates of PaO2 values were compared with conventional measurements of each. Oximeter readings responded rapidly to changes of inspired oxygen concentration and were acceptably accurate estimates of SaO2, except at lower SaO2 levels (less than 80%) during anesthesia without surgery. Transcutaneous oxygen tension readings responded relatively slowly to changes of FIO2 and were frequently inaccurate reflections of PaO2 values. We consider this oximeter suitable as a monitor of arterial oxygenation during anesthesia, but find the transcutaneous electrode unsatisfactory.