A late development model of the Tec 6 vaporizer for the administration of desflurane vapour has been evaluated. It is heated electrically and has both electronic monitors of vaporizer function and alarms. The new filling system is a significant improvement over previous Tec filling systems. The vaporizer requires a warm-up period before it may be used, but when activated it provides an output that is approximately linear between 1 and 18% vapour concentrations, at flow rates between 200 ml min-1 and 10 litre min-1.

SummaryThe output of 30 Tec 3 vaporizers (halothane, enfurane and isofurane) was studied, starting at the point where no liquid was visible in the content window. At 6I.min-' and 1% v/v initial output, consistent delivery was on average maintained for in excess of 90 (range 25120) min. Thereafter, output declined rapidly. At the flows and concentrations studied there is a significant reserve in the vaporizing chamber, but it is likely that when higherflows and concentrations are used this reserve may be substantially reduced. Key words Equipment; vaporizersThe performance of the Tec 3 vaporizer has been extensively described with regard to accuracy, reliability and leakage [l-31, and it is still in widespread use despite two more recent marks of Tec vaporizer. To our knowledge, and after discussion with the manufacturers Ohmeda, one aspect that has not been addressed is the reserve in an apparently empty vaporizer. This is of clinical significance, because although vaporizers are normally refilled before the empty marker is reached, it is quite possible for the anaesthetist's attention to be distracted away from this problem. The aim of this study was therefore to evaluate in a clinical context the output of Tec 3 vaporizers beyond the empty mark on the content window. MethodThirty Tec 3 vaporizers (1 1 delivering enflurane, 7 halothane, and 12 isoflurane), which had been serviced and calibrated within the last year, were evaluated. Each was mounted on the same anaesthetic machine, and filled with the appropriate anaesthetic until the fluid level was visible in the upper third of the content window. After at least 10min had been allowed for the wicks to saturate, the vaporizers were drained until the visible level decreased to within the lower hole communicating with the vaporizing chamber. Carrier gas flows of 6 1.min-' with a mixture of 67% nitrous oxide in oxygen were commenced and the concentration dial adjusted to provide a measured output of 1 % v/v at the common gas outlet of the anaesthetic machine and left at that setting for the remainder of the study. When the meniscus decreased to the lower border of the communicating hole, recording was started. Anaesthetic agent concentration was measured using a Datex Capnomac, which was calibrated prior to each vaporizer assessment. The measured concentration was obtained as an analogue signal from the RS232 interface on the Capnomac, and recorded on a chart recorder for later analysis. The endpoints were the duration of relatively stable output, and the time taken from that point for the output to decrease to 0.5% vlv. ResultsNo attempt to assess the accuracy of these vaporizers was made, as this has already been adequately evaluated. The recording trace obtained (Fig. 1) comprised two parts. The initial phase was relatively stable, but with a slight decrease in the measured output. The second phase was one of a rapid, approximately linear initial decline in the output, followed by a slower tailing off of this decline, until the vaporizer ran dry. In this latter...

An Obligation is an expression of non-functional or cross-cutting requirements, the scope of which transcends any specific service, but for which the service bears an enforcement responsibility. Example use cases include regulations imposed on handling of Electronic Health Records. We describe the concept of an Obligation, provide example use cases, and then define a general design pattern for when a REST developer should consider their use. We then describe a proof-of-concept implementation that extends the Spring Security framework to support the assertion of Obligations within a RESTful service deployment. This extension may be used to inject a range of Obligation behaviors into a REST service during the design, deployment, and post deployment phases. Our prototype is compatible with the XACML 3.0 core standard.

SummaryOne hundred patients scheduled for minor surgery were given either saline, metoclopramide 0.1 mg.kg-' or 0.2mg.kg-', or prochlorperazine 0.1 mg.kg-' or 0.2 mg.kg-' before induction of anaesthesia with a fixed rate infusion of propofol. Neither metoclopramide nor prochlorperazine reduced the induction dose of propofol. The possibility that these agents increased the induction dose could not be excluded.

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