Articles: closed-circuit-anesthesia.
-
Clinical Trial Controlled Clinical Trial
Controlled ventilation using isoflurane with an in-circle vaporiser.
We studied 19 patients anaesthetised for routine surgery using isoflurane delivered from a Komesaroff vaporiser mounted within a circle system. Their lungs were ventilated using a Penlon Nuffield ventilator attached to the circle system by a trunk of tubing. Fresh gas flow rates of 1, 2 or 31.min-1 were used. The inspired agent concentration was measured using a Datex Ultima multigas analyser and was found to be stable and easily controlled.
-
We studied a group of spontaneously breathing patients anaesthetised for routine orthopaedic surgery using a circle system and isoflurane in a Komesaroff vaporiser within the circle. We observed and recorded: (1) the change in inspired isoflurane concentration caused by changing the fresh gas flow, (2) the increased respiration produced by surgical stimulus and the resulting increase in isoflurane concentration, (3) the respiratory depression produced by opioids and the consequent decrease in isoflurane concentration. We consider this regulation of anaesthetic uptake by the patient to be beneficial.
-
In a series of studies designed to investigate the need for a temperature-compensated vaporiser for use in a circle system, we first studied temperature changes within and isoflurane concentration delivered by a Komesaroff vaporiser during bench tests using different gas flows. Agent temperature and vapour concentration decreased as predicted by the Antoine equation. Using the vaporiser within a circle system during clinical anaesthesia, we then studied 20 patients breathing spontaneously and a further 10 patients receiving controlled ventilation, measuring the temperature of the agent within the vaporiser and the concentration of agent inspired by a the patient. In clincial use with the frest gas flows of 1-3.min-1, the inspired agent concentration did not decrease despite the decrease in temperature of the liquid isoflurane in the vaporiser.
-
The performance of the Intersurgical disposable soda lime canister was compared to British Pharmacopoeia standards for carbon dioxide absorption and to other carbon dioxide absorber systems. This canister system more than adequately fulfilled the equivalent of the British Pharmacopoeia standard for CO2 absorption. ⋯ Heat was generated by the reaction between soda lime and CO2 and the maximum temperature recorded in the system was 42.1 degrees C. Under clinical conditions this should pose no threat of thermal injury to the patient.