Anaesthesia
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This study was undertaken to investigate and calibrate the isoflurane output of an Oxford Miniature Vaporiser (OMV) draw-over vaporiser with reversed gas flows. Plenum or Boyles type machines have gas flowing left to right through the apparatus. Draw over anaesthesia systems, in contrast, traditionally have the carrier gas, air plus oxygen, flowing right to left through the vaporiser. ⋯ The predictable output of the OMV vaporiser assumes the correct direction of gas flows for the device. There are many second hand right to left OMV vaporisers for sale to developing countries where the nuances of vaporiser orientation add unnecessarily to the desired simplicity of anaesthesia. A simple calibration scale for reversed gas flows through the OMV vaporiser would be useful.
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Haemodynamic instability is a recognised phenomenon in critically ill patients undergoing hyperbaric therapy. Instability may result from the effects of ambient pressure on the cardiovascular system, devices involved in infusion of drugs and fluids, or a combination of the two. The effect of hyperbaric pressure on air-containing spaces in syringes has not been previously measured. ⋯ There was compression of air spaces within the syringe causing retrograde flow of fluid within the low volume extension set. The mean (95% CI) change in volume was 154 (141-168) microl at 2.4 ATA, and 197 (183-212) microl at 2.8 ATA (both p < 0.0001). We conclude that hyperbaric exposure may cause clinically significant changes in syringe function at infusion rates < 100 ml. h(-1).