Seven different models of oxygen concentrators were purchased. The manufacturer's data were evaluated by a ranking method for operation at high temperature and high relative humidity, power consumption, warranty and cost. Measurements were then made of the oxygen concentration produced at maximum operating temperature. All the concentrators were CE marked and claimed compliance with the relevant Standard ISO 8359:1996. Only two models complied with their specification. On examination of the concentrators and the accompanying documents we found that compliance with 61 points listed in ISO 8359 ranged from 85% to 98%. Oxygen concentration was measured with the machines running simultaneously under both high temperature and high humidity. All models delivered low oxygen concentrations at 40 °C and 95% relative humidity. Only two models delivered >82% at 35 °C and 50% relative humidity. Concentrators intended for use in countries with limited resources should be evaluated before they are purchased, by independent experts, using the methods described herein.
Summary
The design of anaesthesia equipment for use in hospitals in the developing world must take into account the local conditions, particularly whether reliable supplies of compressed oxygen and electricity are available. Designs should ensure that maintenance is feasible locally. International standards should encourage the design of suitable equipment to ensure safe anaesthesia for patients worldwide.
Summary
Sixty patients scheduled for day case surgery were allocated into two groups in a double
Key words.Anaesthesia; outpatient.
Hypnotics; benzodiazepines, temazepamExtensive clinical and laboratory studies have shown temazepam (3 -hydroxydiazepam) to be an effective hypnotic'-3. The pharmacokinetic and metabolic studies of temazepam indicate that the recently introduced soft gelatin capsule preparation4x5 (Normison, Wyeth) might be suitable for oral premedication in day case surgery because of the rapid rise in plasma levels, the short half-life and the lack of active metabolites (in clinically significant amounts).A double-blind trial was therefore undertaken to evaluate the potential of temazepam as a prernedicant in day case surgery.
MethodSixty patients admitted for elective minor surgery as day cases were studied. The age range was 18-70 years, weight 42-85 kg, ASA I or I1 with no recent history of psychotropic drug therapy. The patients, who gave informed consent, were randomly allocated into two groups to be given either temazepam or the placebo on a doubleblind basis. Temazepam 10 mg capsules and placebo capsules of identical appearance were used; patients who weighed less than 60 kg received 20 mg and those who weighed more than 60 kg took 30 mg.Subjective assessments of sedation and anxiety, using 100 mm visual linear analogues, were performed by the patients immediately before premedication and before the induction of anaesthesia 1 hour later. The extremes of the scale recording sedation were marked 'I feel wide ~
SummaryThe Diamedica Draw-Over Vaporizer (DDV) has been developed as an alternative to the Oxford Miniature Vaporizer (OMV). Both can function as draw-over or plenum vaporizers. The performances of these two vaporizers were compared under conditions simulating intermittent positive pressure ventilation (IPPV) and continuous flow (CF). Series 1 experiments were conducted with the vaporizers in water baths at 20, 25 and 30°C. Vaporizers were tested at dial settings of 1-4% over a range of minute volumes (1.75-6 l.min )1 ) and flow rates (3-8 l.min). Series 2 experiments compared output of the vaporizers over time at ambient temperatures of 20, 25 and 30°C. A minute volume of 6 l.min )1 (IPPV) and a gas flow of 8 l.min )1 (CF) were used with a vaporizer setting of 2%. Vapour concentrations were recorded at 5-min intervals. In series 1 IPPV experiments, the DDV vaporizer was more accurate, producing significantly fewer vapour concentrations 0.5% more than or less than setting (p = 0.013). The OMV tended to produce more favourable results under continuous flow (p = 0.42). In series 2 experiments, the accuracy of both vaporizers was similar but consistency of output over time was better for the DDV and consistency of output according to differences in ambient temperature was better for the DDV. The OMV produced more vapour concentrations that were markedly higher than dial setting, particularly at high ambient temperatures. The DDV is a suitable alternative to the OMV with some distinct advantages. These include a larger reservoir, tendency towards greater accuracy during IPPV and improved consistency of output.
SummaryThe Oxyvent is an anaesthetic machine designed specifically for use in the developing world and difficult situations. It is made up of four components, each of which has, in its own right, already proved to be of great value in difficult situations. These are the drawover system, the Penlon Manley Multivent Ventilator, the DeVilbiss Oxygen Concentrator and the air compressor. The four components are mounted on a simple trolley carrying two oxygen cylinders. The Oxyvent can be used to provide anaesthesia in the absence of electricity or oxygen or both. It is simple, robust and easily serviceable. It is versatile and can be used both as an anaesthetic machine in the operating theatre and as a ventilator in an intensive care unit.
Summary
Fifty patients undergoing microsurgery of the ear were anaesthetised using thiopentone, nitrous oxide, oxygen and either halothane or isoflurane, via a low flow circle system with carbon dioxide absorption. Systolic blood pressure was reduced to approximately 70 mmHg by the additional use of increments of labetalol; the patients breathed spontaneously. The degree of haemostasis was assessed by the surgeon who was unaware which volatile agent was being used to supplement anaesthesia. Isoflurane, although it is a potent vasodilator produced operating conditions which were indistinguishable from halothane. Isoflurane is thus a safe and reliable alternative to halothane as a volatile agent used to supplement anaesthesia when using induced hypotension for middle ear surgery.
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