Aspects of the chemistry of polysulphide impression material

The composition, structure and setting reactions of polysulphide impression materials are reviewed in order to correct errors of fact and misinterpretations. A model for molecular size distribution is used to clarify the composition of the prepolymer and the process of setting.     

Effect of humidity on calcium sulphate hemihydrate

The conversion of calcium sulphate hemihydrate powders to dihydrate by reaction with atmospheric water vapour has been re-examined gravimetrically. Storage is usually said to be safe at less than '70 per cent RH', but this is shown to be an inadequate criterion (water vapour pressure being more useful in the context) and based on an inappropriate experiment. At 23 degrees C, greater than about 2.3 kPa water vapour pressure caused rapid reaction, and this may be taken as a more reliable critical value.     

Bile exclusion from the duodenum

The effect of diverting bile from the duodenum in four dogs with cholecystojejunostomy was studied using a double-marker perfusion technique. After the diversion procedure, a liquid meal increased acid secretion from 0.8 mmol H⁺/min to 1.48 mmol H⁺/min (P<0.05, pairedt test); there was an associated rise in serum levels of gastrin 120 min after feeding (P<0.001, pairedt test). Pancreatic secretion of trypsin decreased from 3.91 IU/min to 2.66 IU/min after bile diversion (P<0.01, pairedt test), and the level of CCK was significantly lower 60 min after feeding (P<0.05, pairedt test). There was no significant change in the rate of gastric emptying after bile diversion, but the pH of duodenal contents was lower in the later stages of digestion. These changes may explain the reported increase of peptic ulcer after diverting bile from the duodenum, and the procedure should not be considered unless the consequences of acid hypersecretion and pancreatic inhibition have been anticipated.This work was supported by a grant from the Welsh Scheme for the Development of Health and Social Research.     

A clinical trial of a bead bed system for the prevention of pressure sores in elderly orthopaedic patients

This paper summarizes the results of the trial of the Beaufort Bead Bed system designed to reduce the incidence and severity of pressure sores. Elderly orthopaedic admissions were allocated alternately to the Beaufort system and to the usual trolley, table and bed surfaces, and followed from admission to hospital until separation. The incidence of pressure sores was 15-6% in the 32 'trial' patients, which was significantly less than the 48-8% in the 43 'control' patients, as was the mean maximum diameter of the pressure sores incurred: 6-4 mm for the 'trials' as against 29-5 mm for the 'controls'. In particular the trial group were free from pressure lesions to the heel, which affected 32-6% of the control group. The groups were well matched on a variety of criteria on admission, and we conclude that the Beaufort system successfully reduces the incidence and severity of pressure sores for elderly orthopaedic patients. The system – renamed recently the 'Neumark-Macclesfield Support System'– is now in regular and satisfactory use.     

Supporting structures for team situation awareness and decision making: insights from four delivery suites

Rationale, aims and objectives ‘Human factors’ (non‐technical skills such as communication and teamwork) have been strongly implicated in adverse events during labour and delivery. The importance of shared ‘situation awareness’ between team members is highlighted as a key factor in patient safety. Arising from an ethnographic study of safety culture in the delivery suites of four UK hospitals, the aim of this study is to describe the main mechanisms supporting team situation awareness (TSA) and examine contrasting configurations of supports. Methods Stage I: 177 hours of lightly structured non‐participant observation (sensitizing concepts: safety culture, non‐technical skills, teamwork and decision making) analysed to identify a core organizing concept, main supporting categories and preliminary conceptual models. Stage II: (approximately 11 months after first observations) 104 hours of observation to test and elaborate stage I analyses. Results Handover, whiteboard use and a coordinator role emerged as the key processes facilitating work and team coordination. The interplay between these supporting processes and the contextual features of each site promoted or inhibited TSA. Three configurations of supports for TSA were evident. These are described. Conclusions Context configurations of supporting mechanisms and artefacts influence TSA, with implications for the maintenance of patient safety on delivery suites. A balanced model of supports for TSA is commended. Examining contrasting configurations helps reveal how local mechanisms or organizational, environmental and temporal factors might be manipulated to improve TSA.     

Nurse manpower demand: a review of United Kingdom methodologies

Forecasting the demand for nurses is a complex and difficult problem However, in a climate of economic cutbacks and disadvantageous demographic trends, it is essential that adequate methods are developed to predict both the supply and demand for nurse manpower To this end a number of methods have been constructed, particularly in the last decade In this paper we survey the work that has been done to provide an effective way of forecasting nurse manpower demand The two most common approaches are from the 'top-down' or 'bottom-up' However, an evolutionary method which allows for modification and detailed refinement is more likely to provide a means of taking into account the complexities of the system Finally, we focus on the nursing hours per patient (NHPP) ratio as a possible tool for demand forecasting This index is easily calculated and is readily adaptable to the bottom-up approach