Inspiratory work imposed by continuous positive airway pressure (CPAP) machines: the effect of CPAP level and endotracheal tube size.

Inspiratory work imposed by Continuous Positive Airway Pressure (CPAP) machines has been a matter of concern. The imposed inspiratory work of CPAP machine circuits (Wcir) and the effect of the total breathing apparatus with endotracheal tube (ETT) and connector included in the circuit (Wapp), were measured in three continuous flow (CF) and various configurations of three demand flow (DF) CPAP machines. The performance was assessed at 0, 5, 10 and 15 cmH2O CPAP using a Michigan Instruments Test Lung Model 1600, internal compliance set at 50 ml/cmH2O, driven at square wave inspiratory flows (VI) of 20, 40 and 60 l/min at a tidal volume of 500 ml. Work, expressed in mJ/l, was calculated from the area of pressure-volume loops. Inspiratory work, Wcir and Wapp, was dependent upon the particular CPAP machine, VI and ETT size, but not upon CPAP level, being maximum at VI 601/min and with ETT 7.0 mm i.d. Work values (Wcir) varied from 50 to 325 mJ/l with both CF and DF machines and up to 1100 mJ/l with ETT and connector (Wapp). No consistent advantage of CF over DF machines was demonstrated. There was little advantage of high gas flows (greater than 5 l/min) in various DF circuits. Within an individual machine maximum negative pressures generated during inspiration correlated with both Wcir and Wapp.

Hypocortisolaemia and adrenocortical responsiveness at onset of septic shock.

OBJECTIVE: To characterise the plasma cortisol profile and adreno-cortial responsiveness (short Synacthen test) of patients in septic shock. DESIGN: Retrospective assessment using case-notes and ICU charts. SETTING: University teaching hospital ICU. PATIENTS: 68 septic shock patients with plasma cortisol and/or short Synacthen test measured at ICU-admission or onset of shock post ICU-admission. Patients were identified from a total population of 155 patients who had PCL and/or SST measured over a 4.5 year period. INTERVENTION: None. MEASUREMENTS AND RESULTS: Patients with septic shock had a plasma cortisol ranging from 210-8900 nmol/l and mortality of 56%. There were 22 (32%) below (low) and 46 (68%) above (high) a 'critical' plasma cortisol of 500 nmol/l. Using stepwise logistic regression, mortality was adequately predicted by and increased with, increasing plasma cortisol and onset of shock remote from ICU-admission. Short Synacthen tests were available in 33 patients: 11 responders (cortisol increment > 200 nmol/l above baseline 30 min after 0.25 mg intravenous Synacthen) and 22 hypo-responders. Mortality in patients was adequately predicted by and increased with a decrease in cortisol increment post-Synacthen. Thirteen patients (plasma cortisol 606 +/- [SD] 297 nmol/l) had complete haemodynamic profiles before inotropic therapy; no relationship was demonstrated between plasma cortisol and circulatory variables. Follow-up revealed no cases of Addison's disease. CONCLUSIONS: In septic shock, 'hypocortisolaemia' is not uncommon and does not predict a high mortality; adrenocortical hypo-responsiveness may be associated with poor outcome.

Microvascular luminal volume changes in aged mouse periodontal ligament.

Data for the microvascular bed in the aged periodontal ligament have not been established. This investigation tested the hypothesis that the luminal microvascular volume decreased in the aged ligament. Mice 35 days old and one year old were vascular-perfused and the mandibular first molar periodontal ligament processed for electron microscopy. Tissue quadrats from each circumferential third ligament region were recorded at 150-microns intervals from the alveolar crest to the apex for randomized sampling of blood vessel lumina. The data were analyzed with a generalized linear model at the p < 0.01 level for the interaction of the aging effect with differences across regions. Stereological parameters were established for vessel lumen volume, and for surface and length densities. Mean ligament width decreased from 119.9 +/- 16.94 (micron +/- SE) in young mice to 60.0 +/- 10.58 (micron +/- SE) in aged mice. The luminal volume of 8.63 +/- 1.37 (% +/- SE) in young ligament increased to 9.83 +/- 2.14 (% +/- SE) in aged ligament. Collecting venules and the combined group of arterio-venous anastomoses with terminal arterioles showed a two-fold increase in luminal volume density (p < 0.01). In aged ligament, regional shifts affected the microvascular bed distribution, but these changes were not consistent across regions, or with depth. The average cross-sectional tissue area served per capillary decreased from 2117 microns 2 to 1451 microns 2 for young and old. Average ligament thickness served per capillary dropped from 52.5 microns to 27.5 microns. These reductions in average diffusion distances indicated a change in the quality of the diffusion barrier with age.

A review of the technical features of breast cancer screening illustrated by a specific model using South Australian cancer registry data.

This paper illustrates many of the concepts and issues relating to breast cancer screening by reference to a case study of screening in South Australia and by a survey of the mathematical screening models. This work is motivated by the observation that, for some women, the prospects for a breast cancer cure appear to be enhanced if the disease is detected early. We use data from the South Australian Cancer Registry to estimate some of the parameters which describe the pattern of this disease in the South Australian female population, and the underlying model is then used to estimate the impact of various screening designs on the efficacy of a variety of breast cancer screening programmes.

Survival predictions of amalgam restorations.

The purpose of this study was to evaluate survival predictions made for four different amalgam alloy restorations, using a mixture model involving the standard Weibull function. The amalgam alloys were placed by students and staff in patients attending a dental hospital, and 1680 restorations were examined over periods of up to 18 years. Based on maximum likelihood estimations of the parameters of the mixture model distribution, predictive survival distributions were generated and found to match closely the actuarial survival estimates established from the same data. The 13-year restoration survivals of one low-copper alloy could be predicted accurately from the 6-year survival results. However, another low-copper alloy and two high-copper alloys with much lower restoration failure rates required 18 years of data for accurate long-term survival predictions.

Survival predictions of four types of dental restorative materials.

The present study assessed the survival predictions made for four different types of dental restorative materials, using a mixture model involving the standard Weibull distribution function. A large number of amalgam, anterior resin, glass polyalkenoate (ionomer) cement, and pit and fissure sealant restorations were examined over varying periods of up to 18 years. The materials had been placed by numerous staff and students at a teaching hospital. Based on maximum likelihood estimations of the parameters of the mixture model distribution, survival curves were generated and found to agree closely with the actuarial survival curves estimated from the same data. As the years of data used to fit the mixture model curves decreased, then the fitted curves started to exhibit obvious divergences from the actuarial curves at 12-13 years for amalgams, 3-4 years for anterior resins and sealants, and 1-2 years for glass polyalkenoate (ionomer) cements. At least 5 per cent of restorations needed to have failed over any period to allow close agreement of the two curves, with the slower failing materials requiring longer observation periods.

Predictions of restoration deterioration.

This study evaluated the application of a mixture model involving a Weibull distribution function to predict the median times for restorations of three dental restorative materials to achieve unsatisfactory rating scores for six clinical factors. The accuracy of the method was assessed graphically against the known actuarial long-term deterioration observations of 1813 amalgam, 1774 anterior resin composite and 474 glass polyalkenoate (ionomer) cement restorations, assessed over periods of up to 20, 18 and 14 years, respectively. Of the six clinical factors investigated (which included marginal fracture), only four had sufficient long-term unsatisfactory rating score data to enable their median times to be predicted. These predicted times were: for amalgam restorations, surface roughness 32.5 years and surface tarnishing 16.0 years; for resin composites, marginal staining 25.4 years and colour mismatch 14.2 years; and for glass polyalkenoate (ionomer) cements, marginal staining 17.6 years and colour mismatch 3.6 years. The known and predictive unsatisfactory rating score results were generally in close agreement. However, it was not possible to predict median times for unsatisfactory rating scores associated with very slowly deteriorating restoration factors. The actual replacement rates of the amalgam restorations were too low to obtain their median survival time. However, for the faster failing resin composites this time was 7.9 +/- 0.5 years, and for the glass polyalkenoate (ionomer) cements 2.2 +/- 0.2 years. The relationship of restoration deterioration to restoration replacement and dental health requires further analysis.

Prediction of amalgam restoration longevity.

The purpose of the present study was to assess predictions of longevity for amalgam restorations using a fitted Weibull distribution against base estimates using actuarial methods. The 1345 restorations involved were from 100 members of the Royal Australian Air Force whose dental conditions had been monitored regularly over a minimum period of 10 years. Based on maximum likelihood estimates of the parameters of a Weibull distribution, Weibull curves could be determined and were found to be very close to actuarial survival curves established from the same data set. However, Weibull estimates based on survival experience of less than 5-6 years failed to predict long-term survival. Using the 6 year actuarial survival data, the predicted and observed survival curves disagreed by less than 10 per cent for every time period. Twenty-five per cent of restorations had failed for the 6 year data, compared to 22 per cent in these first 6 years for the full 17 year data set.

The costs of coronary artery surgery to the community.

The possible benefits obtained both for the community and patients following coronary artery bypass grafting (CABG) have been examined in 4001 patients (mean age 54 years, 14.8% female) who underwent CABG from 1971 to 1982 in the Cardiothoracic Surgical Unit of the Royal Adelaide Hospital. Assessment followed a fixed response format questionnaire sent to all patients with a total follow-up of 98.8%. The hospital mortality was 1.4% for the 10 year period with a fall from 4% in 1973 to 0.9% in 1981. Shifts in employment were assessed in survivors. At follow up, 548 patients who were previously employed had ceased full-time or part-time employment. This decrease in employment was attributed mainly to age. Analysis of retirement curves for the general male population and male patients showed a similar pattern but downward translation of 4% for the pre-operative group. A similar downward shift occurred following surgery. For female patients, performance of home duties improved from 159 patients on full home duties pre-operatively to 292 post-operatively. Visits to the doctor dropped in 50% of surviving patients. CABG has a low mortality. The community benefits by helping to maintain productivity and decreased cost for ongoing medical care.

A 4-year experience with the Björk-Shiley Monostrut valve.

We reviewed 314 consecutive patients in whom a Björk-Shiley Monostrut aortic valve prosthesis was inserted by our cardiothoracic surgical unit from June 1982 through June 1986. The group comprised 220 males (70%) and 94 females (30%), with a mean age of 60 years (range, 5 to 83 years). Two hundred ninety-six patients (94%) received an aortic prosthesis alone, and the other 18 (6%) received both an aortic Monostrut valve and a Starr-Edwards mitral valve prosthesis. In each case, preoperative data were collected prospectively, and a questionnaire was sent at the time of follow-up. The median follow-up period was 23 months (range, 0 to 46 months); 6 (2%) of the patients were lost to follow-up. In the remaining 308 cases, there were 20 deaths (6.5%), 8 of which occurred within approximately 1 month after operation. There were no known instances of valve failure. One death occurred in the group that underwent double-valve replacement. Valve endocarditis accounted for 2 late deaths. With respect to preoperative dyspnea, 59 (19%) of the patients were in New York Heart Association functional Class I, 74 (24%) were in Class II, 138 (45%) were in Class III, and 37 (12%) were in Class IV. Postoperatively, there were 247 patients (80%) in Class I, 43 (14%) in Class II, 15 (5%) in Class III, and 3 (1%) in Class IV (p < 0.0001). All of the patients received postoperative anticoagulant therapy; 3.4% per year were subsequently readmitted for bleeding problems. Thromboembolic events necessitating hospitalization occurred in 3.0% of the patients per year. On the basis of these results, our early experience with the Björk-Shiley Monostrut valve in the aortic position has been satisfactory, with an acceptable rate of complications and no documented valve failures.

Primitive neuroepithelial tumours of soft tissues and of bone: further ultrastructural and immunocytochemical clarification of 'Ewing's sarcoma', including freeze-fracture analysis.

The ultrastructural appearances of 7 primitive neuroepithelial tumours (PNETs) originating in soft tissues and bone are described. Three of the tumours represented primary soft tissue lesions, while locally recurrent tumour or pulmonary metastases were studied from the 4 skeletal tumours, all of which had been diagnosed previously as Ewing's sarcomas. Rosettes were present in one of the soft tissue lesions and although not seen in the primary skeletal neoplasms, they were identified by light microscopy (LM) in 2 of 3 pulmonary metastases, one of which had the morphology of a neuroepithelioma, with innumerable Homer Wright rosettes. Conventional TEM revealed cytoplasmic processes in all cases and rosettes in varying stages of development were also evident, but the appearances did not achieve the level of cellular organization seen in neuroblastoma: microtubules were few, while dense-core granules varied in number but were generally sparse and pleomorphic, resembling lysosomes. However, typical neurosecretory granules were found in one lung metastasis; the neoplastic cells comprising the same tumour also had epithelial markers in the form of well constructed desmosomes, while freeze-fracture analysis demonstrated elaborate tight junctions. In thin sections, junctions in the other tumours appeared rudimentary, but freeze-fracture of a further case revealed small collections of membrane particles suggesting extremely poorly developed desmosomes. Immunocytochemical study of 4 tumours (2 originating in soft tissue and 2 in bone) demonstrated weak to moderate immunostaining for neurone-specific enolase and with several monoclonal antibodies reactive with neuroblastomas, but there was no evidence of immunolabelling for tyrosine hydroxylase.(ABSTRACT TRUNCATED AT 400 WORDS)

Oral hygiene home care kits: effects on the dental behaviour of kindergarten children.

Oral hygiene kits issued directly to children of kindergarten age positively influenced their dental care behaviour. Significantly increased percentages of children changed to using the clinically proven fluoride toothpaste, an approved type of toothbrush, and disclosing tablets, the three oral hygiene aids included in the kit.

The dental care of handicapped children in South Australia.

Sixty-two per cent of handicapped children had a dentist willing to provide treatment; 55 per cent and 41 per cent were examined and were treated at least annually. Approximately 58 per cent were reported by their guardians to be manageable in general dental practice. Treatment was provided under general anaesthesia for 29 per cent of the children, although 39 per cent were considered by their guardians to require this procedure. Factors related to type and frequency of dental treatment are discussed.

Handicapped children: behavioural and co-ordination characteristics affecting the delivery of dental care.

Statistical analysis of data from a field survey of 132 handicapped children confirmed that a questionnaire approach is reliable in identifying children with potential behavioural and co-ordination problems within a dental environment. Assessment of the behaviour and co-ordination of 2,082 handicapped children aged 3-16 years, inclusive, suggested that approximately 53 per cent were manageable in a normal dental surgery and 79 per cent had the necessary co-ordination for routine dental care.

The handicapped child population in South Australia in 1975.

A survey of 2,212 handicapped children was conducted in South Australia to provide basic information so that a dental service could be planned. The prevalence of various specified conditions is presented for both single and combined disabilities. The distribution of the various conditions between the sexes has been analysed.

Is length of life predictable?

A random sample of death records of adult males from the period 1967 to 1970 was chosen from the South Australian Registry of Births, Deaths, and Marriages. The natural parents of these individuals were identified by cross-referencing to birth certificates, and an extensive search was made of the death records for these parents. In this manner random families were selected for which, where possible, the cause of death and length of life of each family member were determined. Here, we analyze the association between sons and their parents in length of life and report the statistically useful correlations that were found. These correlations enable the calculation of a life table for a male conditional on his current age and the lifetimes of his parents. Comparisons are made with the uninformed population life table based solely on sex and year of birth.