Sevoflurane for analgesia-testing a modified vaporiser for delivery

The Diamedica Sevoflurane Inhaler (Diamedica UK Ltd, Bratton Fleming, UK) (DSI) is a breathing system which includes a modification of an existing vaporiser (Diamedica Draw-over Vaporiser, Diamedica UK Ltd, Bratton Fleming, UK), to enable the delivery of 0.8% sevoflurane. Previous studies have suggested that self-administered sevoflurane at sub-anaesthetic concentration can provide useful pain relief during the first stage of labour and that it may be more effective than Entonox. Further research and potential clinical use have been impeded by the lack of a practical delivery system. In this study, the performance of two versions of the DSI (DSI-1 and DSI-2) was investigated. DSI-1 was tested over a range of minute volumes (1 to 30 l/min) and ambient temperatures (10°C to 40°C). The sevoflurane output increased unacceptably with rising ambient temperature, therefore the design was modified to create the DSI-2. The results from testing this revised version are also described. Mean sevoflurane output from the DSI-2 was found to be within a clinically acceptable range at the minute volumes tested (0.78% to 0.88%) and ambient temperatures tested (0.69% to 0.9%). Based upon these results, the authors propose to undertake further studies of sevoflurane analgesia using the DSI-2.

Evaluation of oxygen concentrators for use in countries with limited resources

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.

Modification of a draw-over vaporizer for use with sevoflurane

BACKGROUND

Draw-over anaesthesia is widely used throughout the developing world, in disaster areas and in military anaesthesia when the supply of pressurized oxygen is unreliable. To date, no draw-over vaporizer has been able to deliver sufficient concentrations of sevoflurane for use in inhalation induction of anaesthesia. A laboratory study to assess the performance of a new vaporizer (DDV2) to deliver sevoflurane in a wide range of situations is described.

METHODS

In this study, the concentration of sevoflurane delivered at different dial settings (1-4%) and at different temperatures (20-40°C) in a draw-over mode was measured. The concentration of sevoflurane delivered at different dial settings with continuous flow (6 and 8 litre min(-1)) at 20°C was measured. The maximum possible concentration of sevoflurane that can be delivered by the DDV2 was measured at a continuous flow rate of 8 litre min(-1) at 20, 30, and 40°C.

RESULTS

Concentrations of sevoflurane delivered in the draw-over mode were within 0.5% of dialled setting up to 30°C. Above this temperature, higher levels of vapour were delivered. With continuous flow, concentrations of sevoflurane at 20°C were within 0.5% of dialled setting and were stable throughout the duration of the experiment. On the 'induction' setting, concentrations of sevoflurane of between 6.4% and 10.1% could be delivered with continuous flow.

CONCLUSIONS

The modifications to the DDV2 allow stable concentrations of sevoflurane to be delivered in draw-over and continuous flow modes over a range of temperatures. With continuous flow, concentrations of sevoflurane sufficient for induction of anaesthesia can be achieved.

Achieving acceptable reliability in oral examinations: an analysis of the Royal College of General Practitioners membership examination's oral component

BACKGROUND

The membership examination of the Royal College of General Practitioners (RCGP) uses structured oral examinations to assess candidates' decision making skills and professional values.

AIM

To estimate three indices of reliability for these oral examinations.

METHODS

In summer 1998, a revised system was introduced for the oral examinations. Candidates took two 20-minute (five topic) oral examinations with two examiner pairs. Areas for oral topics had been identified. Examiners set their own topics in three competency areas (communication, professional values and personal development) and four contexts (patient, teamwork, personal, society). They worked in two pairs (a quartet) to preplan questions on 10 topics. The results were analysed in detail. Generalisability theory was used to estimate three indices of reliability: (A) intercase (B) pass/fail decision and (C) standard error of measurement (SEM). For each index, a benchmark requirement was preset at (A) 0.8 (B) 0.9 and (C) 0.5.

RESULTS

There were 896 candidates in total. Of these, 87 candidates (9.7%) failed. Total score variance was attributed to: 41% candidates, 32% oral content, 27% examiners and general error. Reliability coefficients were: (A) intercase 0.65; (B) pass/fail 0.85. The SEM was 0.52 (i.e. precise enough to distinguish within one unit on the rating scale). Extending testing time to four 20-minute oral examinations, each with two examiners, or five orals, each with one examiner, would improve intercase and pass/fail reliabilities to 0.78 and 0.94, respectively.

CONCLUSION

Structured oral examinations can achieve reliabilities appropriate to high stakes examinations if sufficient resources are available.

Assessing validity in written tests of general practice - exploration by factor analysis of candidate response patterns to paper 1 of the MRCGP examination

OBJECTIVE

To investigate the content validity of Paper 1 of the MRCGP examination.

METHOD

Exploratory factor analysis was carried out on candidate responses to Paper 1 of the May and October MRCGP examination in 1998. Contribution of each test question across factors was assessed using a pattern matrix of the oblique rotation. Common dimensions and variations between factor sets were identified. Key testing areas were then matched against the 'domains of competence' intended to be assessed by Paper 1 (as defined within the examination blueprint matrix).

RESULTS

Whilst critical appraisal, disease prevention/evidence-based medicine and clinical management emerged as areas tested consistently, content variation was observed between factor sets extracted from both sittings. In addition, some overlap, in terms of domains tested, was seen among other assessment instruments used within the examination.

CONCLUSION

Paper 1 conforms to the majority of its stated intentions. However, further development of techniques for investigating validity will be required in order to minimize content variation between both sittings of the examination as well as to help more closely define areas of competence to be tested by Paper 1 of the MRCGP examination.

Assessing physicians' interpersonal skills via videotaped encounters: a new approach for the Royal College of General Practitioners Membership examination

The Royal College of General Practitioners' Membership examination, the only postgraduate qualification in family medicine in the United Kingdom, has developed a direct assessment of candidates' interpersonal skills performance using videotaped consultations of the actual doctor-patient encounters. At present about 1,200 doctors are examined each year. The methodology has been developed and piloted over a period of eight years. The central tenet of the methodology is a clear definition, which is known both to the candidate and to the examiner, of the clinical and consulting competencies that are required to be demonstrated in order to pass the examination. The candidate is required to provide evidence of his or her competence usually by selecting appropriate patient encounters that demonstrate the fulfillment of the required performance criteria, effectively producing a portfolio of his or her communicative competence. The methodology is intended to encourage the learning and teaching of communication skills by making it part of an important examination and clearly defining the competencies required to pass. Reliability has been demonstrated to be satisfactory and refinement of the marking processes is likely to improve this further.

Family therapy by family doctors

The experiences of a group of general practitioners learning and attempting family therapy are described. Three principles for working with whole families - facilitation, formulation and focussing - are illustrated by case histories. Family therapy in general practice can be effective for patients and worthwhile for family doctors.

Antenatal memories and psychopathology

A case is described of suicidal impulses apparently stemming from the patient's experience before and during his birth. By using a technique of ;rebirthing', antenatal memories were relived and their traumatic effects resolved. Theoretical and practical accounts of rebirthing are given, and its significance for general practitioners is discussed.