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Biomedical subjects

C M Conway

Publications and source records attributed to C M Conway.

At least 37 records · Page 2Linked to original sources
PubMed1976

A theoretical study of gaseous homeostasis in the Magill circuit.

Equations have been derived to determine the alveolar gas concentrations which occur when the Magill (Mapleson A) circuit is used with a low fresh gas flow. Alveolar oxygen and carbon dioxide concentrations are determined by the fresh gas flow and composition, carbon dioxide output and oxygen uptake. Gas mixing within the circuit and alterations in the inspired gas concentrations do not affect the final equilibrium. If oxygen uptake and carbon dioxide output are constant, the alveolar gas concentrations are unaffected by alterations in ventilation.

Anesthesia, Inhalation↗
PubMed1976

An experimental study of gaseous homeostasis and the Magill circuit using low fresh gas flows.

Gas concentrations and ventilation levels have been measured within a conventional Magill circuit when conscious volunteers breathed a non-narcotic gas mixture at varying fresh gas flows. When evidence of rebreathing of alveolar gas was detected, the fresh gas flow was kept constant until a steady state developed. All subjects showed evidence of rebreathing when the fresh gas flow approached the predicted alveolar ventilation levels. A variety of subject-circuit interactions was seen and shown to be precipitated by naturally occurring breath-to-breath variations in ventilation. A single large breath could perturb the system. This could have a temporary effect, when the fresh gas flow was sufficient to wash the increased aliquot of expired carbon dioxide from the circuit. At other times a progressive response occurred as ventilatory stimulation as a result of the increased inspired carbon dioxide concentrations caused alveolar gas to reach the reservoir bag and converted the system behaviour from that of a simple added deadspace to that of a total mixing device. Whilst marked changes occurred commonly in both ventilation and inspired gas concentrations, only slight changes in end-tidal gas concentrations occurred.

Anesthesia, Inhalation↗
PubMed1976

The Lack anaesthetic system. An assessment during spontaneous ventilation.

The Lack anaesthetic system is a coaxial modification of the Magill circuit. The resistance of the system was found to be unacceptably high. When air was administered through the system to spontaneously breathing trained volunteers, marked evidence of rebreathing was present when fresh gas flow equalled minute volume. It is suggested that a fresh gas glow equal to one and a half-times minute volume would be required to prevent rebreathing of alveolar gas.

Anesthesia, Inhalation↗