On the distance to the North Polar Spur and the local CO-H2 factor

AIMS

Most models identify the X-ray bright North Polar Spur (NPS) with a hot interstellar (IS) bubble in the Sco-Cen star-forming region at ≃130 pc. An opposite view considers the NPS as a distant structure associated with Galactic nuclear outflows. Constraints on the NPS distance can be obtained by comparing the foreground IS gas column inferred from X-ray absorption to the distribution of gas and dust along the line of sight. Absorbing columns towards shadowing molecular clouds simultaneously constrain the CO-H₂ conversion factor.

METHODS

We derived the columns of X-ray absorbing matter N _Habs from spectral fitting of dedicated XMM-Newton observations towards the NPS southern terminus (l ^II ≃ 29°, b ^II ≃ +5 to +11°). The distribution of the IS matter was obtained from absorption lines in stellar spectra, 3D dust maps and emission data, including high spatial resolution CO measurements recorded for this purpose.

RESULTS

N _Habs varies from ≃ 4.3 to ≃ 1.3 × 10²¹ cm^-2 along the 19 fields. Relationships between X-ray brightness, absorbing column and hardness ratio demonstrate a brightness decrease with latitude governed by increasing absorption. The comparison with absorption data, local and large-scale dust maps rules out a NPS near side closer than 300 pc. The correlation between N _Habs and the reddening increases with the sightline length from 300 pc to 4 kpc and is the tightest with Planck τ _353GHz -based reddening, suggesting a much larger distance. N(H)/E(B-V) _τ ≃ 4.1 × 10²¹ cm^-2 mag^-1, close to Fermi-Planck determinations. N _Habs absolute values are compatible with HI-CO clouds at -5 ≤ V _LSR ≤ +25 to +45 km s^-1 and a NPS potentially far beyond the Local Arm. A shadow cast by a b=+9° molecular cloud constrains X _CO in that direction to ≤ 1.0 × 10²⁰ cm^-2 K^-1 km^-1 s. The average X _CO over the fields is ≤ 0.75 × 10²⁰ cm^-2 K^-1 km^-1 s.

A mathematical model of CO2 variation in the ventilated neonate

A mathematical model of the variation of partial pressure of carbon dioxide in the arterial blood of a ventilated neonate is developed. The model comprises alveolar, arterial, pulmonary, venous and tissue compartments, with gas exchange in the lung determined by inspiration and expiration terms. Gas exchange is modelled through diffusion and convective transfer. Carbon dioxide is produced in the tissue by a metabolic term. Shunting is modelled by allowing blood flow to bypass the pulmonary compartment in which diffusion takes place. The model predicts changes in the carbon dioxide partial pressures that occur following abrupt changes in the ventilation settings, and show broad agreement with actual data obtained from novel sensing technology.

Friction burns within the tibia during reaming

We have carried out a prospective, randomised trial to measure the rise of temperature during reaming of the tibia before intramedullary nailing. We studied 34 patients with a mean age of 35.1 years (18 to 63) and mean injury severity score of 10 (9 to 13). The patients were randomised into two groups: group 1 included 18 patients whose procedure was undertaken without a tourniquet and group 2, 16 patients in whom a tourniquet was used. The temperature in the bone was measured directly by two thermocouples inserted into the cortical bone near the isthmus of the tibial diaphysis. Reaming was carried out to at least 1.5 mm above the required diameter of the nail. Blood loss was assessed by recording the preoperative and postoperative haemoglobin (Hb) level.

The minimum clinical follow-up was six months. In group 1 (no tourniquet), the mean Hb dropped 2.8 g/dl from 14.3 ± 1.02 g/dl to 11.5 ± 1.04 g/dl (p = 0.0001), whereas with the tourniquet, the mean decrease was 1.3 g/dl from 14 ± 1 g/dl to 12.7 ± 1.3 g/dl (p = 0.007). This difference was not statistically significant. The mean initial tibial temperature was 35.6°C (sd 0.6) and rose with reaming to levels between 36.3°C and 51.6°C. The highest temperatures were obtained with the largest reamers (11 and 12 mm, p = 0.0001) and the most rapid rise with the smallest diameters of medullary canal (8 or 9 mm). The rise of temperature was transient (20s).

We were unable to identify any effect of the use of a tourniquet on the temperature achieved. Reamed intramedullary tibial nailing induces a transient elevation of temperature which is directly related to the amount of reaming.

Friction burns within the tibia during reaming. Are they affected by the use of a tourniquet?

We have carried out a prospective, randomised trial to measure the rise of temperature during reaming of the tibia before intramedullary nailing. We studied 34 patients with a mean age of 35.1 years (18 to 63) and mean injury severity score of 10 (9 to 13). The patients were randomised into two groups: group 1 included 18 patients whose procedure was undertaken without a tourniquet and group 2, 16 patients in whom a tourniquet was used. The temperature in the bone was measured directly by two thermocouples inserted into the cortical bone near the isthmus of the tibial diaphysis. Reaming was carried out to at least 1.5 mm above the required diameter of the nail. Blood loss was assessed by recording the preoperative and postoperative haemoglobin (Hb) level. The minimum clinical follow-up was six months. In group 1 (no tourniquet), the mean Hb dropped 2.8 g/dl from 14.3 +/- 1.02 g/dl to 11.5 +/- 1.04 g/dl (p = 0.0001), whereas with the tourniquet, the mean decrease was 1.3 g/dl from 14 +/- 1 g/dl to 12.7 +/- 1.3 g/dl (p = 0.007). This difference was not statistically significant. The mean initial tibial temperature was 35.6 degrees C (SD 0.6) and rose with reaming to levels between 36.3 degrees C and 51.6 degrees C. The highest temperatures were obtained with the largest reamers (11 and 12 mm, p = 0.0001) and the most rapid rise with the smallest diameters of medullary canal (8 or 9 mm). The rise of temperature was transient (20 s). We were unable to identify any effect of the use of a tourniquet on the temperature achieved. Reamed intramedullary tibial nailing induces a transient elevation of temperature which is directly related to the amount of reaming.

Temperature rise during reamed tibial nailing

The current study determined the temperature rise during reamed tibial intramedullary nailing in vivo. Eighteen adult patients were studied. The tibial medullary canal diameter ranged from 8 to 11 mm and was reamed to at least 1.5 mm above the required nail diameter with AO reamers. Reaming of the medullary cavity ranged from 9 to 12 mm before nail insertion. Intraoperative monitoring of the heat produced during reaming of the medullary cavity was done by inserting two platinum resistance thermometer probes into the cortical bone at the short isthmic segment of the tibial shaft. The probes were connected to a data logger, and temperature readings were taken every 5 seconds during each reaming procedure. The mean tibial temperature before initiation of reaming was 35.6 degrees C (standard deviation, +/- 0.5 degrees), and peak temperatures recorded were from 36.1 degrees C to 51.6 degrees C. A direct correlation was observed between temperature elevation and amount of reaming. With reaming above 10 mm, tibias with a canal diameter of 8 mm showed a statistically higher temperature rise compared with tibias with a canal diameter of 9, 10, or 11 mm. No patients had intraoperative or postoperative complications related to skin or bone thermal necrosis, and bony healing progressed uneventfully. The small amount of reaming required to insert a nail into a normal 9-, 10-, or 11- mm tibial canal does not seem to produce a clinical problem. Reaming smaller canals (8 mm) to a larger size may induce a significant heating effect.

European randomised trial of dual versus triple tacrolimus-based regimens for control of acute rejection in renal allograft recipients

Two large multicentre studies have shown superiority of tacrolimus-based immunosuppressive regimens compared with standard cyclosporine-based therapy in renal transplantation. In these studies, tacrolimus was used in a triple drug regimen of tacrolimus, corticosteroids, and azathioprine. The present study aimed to determine whether a tacrolimus-based dual regimen achieves a similar efficacy and safety profile compared with conventional triple therapy. In this prospective, open, multicentre trial, 249 patients were randomised to receive either dual therapy (n = 125) of oral tacrolimus (initial daily dose of 0.2 mg/kg) and oral prednisone or additionally, as a triple therapy (n = 124), oral azathioprine. The primary endpoint was the incidence of acute rejection at month 3. In addition, all patients were included into a follow-up evaluation at 1 year after transplantation. Both treatment groups had similar baseline characteristics. At month 3, patient survival was 97.6 % (dual) and 96.7 % (triple); graft survival was 92.7 % (dual) and 91.7 % (triple). The incidence of treated acute rejection confirmed by biopsy was 27.4 % (dual) and 24.8 % (triple); difference 2.6 %, 95 % CI [-9.4 %-12.9 %], P = 0.755. The incidence of corticosteroid-resistant rejection (biopsy-confirmed) was 9.7 % (dual) and 10.7 % (triple). The overall adverse events profile was similar; leukopenia (1.6 % vs 11.6 %, P = 0.002) was more frequent with triple therapy. Between months 4 and 12, six (dual) and eight (triple) patients had a rejection. At month 12, patient survival was 95.6 % (dual) and 93.6 % (triple); graft survival was 91.8 % (dual) and 90.7 % (triple). Tacrolimus proved to be efficacious and safe with both dual and triple low-dose regimens. The addition of azathioprine to a tacrolimus/corticosteroid-based therapy did not result in an increased efficacy.

A digital system for recording the electrical activity of the uterus

The ability to identify true pre-term labour would be of considerable clinical benefit as electrical signals from the uterus, recorded using surface electrodes, may discriminate between labouring and non-labouring states in human pregnancy. A digital recording system for recording the electrical activity of the uterus has been developed and is described in this paper. A pilot study in which entire recordings in 21 women were subjected to power spectral analysis suggests that the relative power in two frequency bands (0.2-0.45 Hz and 0.8-3 Hz) changes as pregnancy progresses into early labour.

General practitioner participants in a telemedicine trial: comparisons with their peers

A study was conducted to determine whether general practitioners (GPs) participating in a telemedicine trial were self-selected enthusiasts for information technology compared with GPs in general. We compared two experimental groups of GPs in London and Wales (n = 126) who had volunteered to participate in a telemedicine trial and two randomly selected groups of GPs from the same areas (total n = 300) who acted as controls. A postal questionnaire was used and achieved a 79% response rate. There were no significant differences in the demographic characteristics of the experimental and control groups in London and Wales, except that the London telemedicine GPs (mean age 41.9 years) were significantly younger than the London controls (mean age 46.6 years). The control GPs were similar to the telemedicine GPs in terms of frequency of computer use and their responses to statements about their attitudes to computers. In the combined telemedicine and control groups, 85% and 77% respectively said that they enjoyed using computers. Telemedicine GPs used computers more frequently for administrative purposes but they shared the same attitudes towards information technology as GPs in general. In all situations where GPs could exercise personal choice, the control and experimental groups were similar.

Ruptured abdominal aortic aneurysm: a novel method of outcome prediction using neural network technology

BACKGROUND

reported survival following emergency surgery for ruptured abdominal aortic aneurysm (RAAA) varies widely between institutions. This is largely attributable to differences in case mix. The aim of this study was to identify and evaluate a set of prognostic variables that would accurately predict outcome for individual patients from perioperative indices.

METHODS

perioperative factors associated with subsequent mortality at our institution were identified by retrospective review of 102 consecutive operations for RAAA over a 7-year period (January 1990 to January 1997). Logistic regression analysis was used to select the most significant variables associated with subsequent mortality. These were used to construct, train, and validate a neural network designed to predict survival from surgery in individual cases on a prospective basis.

RESULTS

the 30-day mortality rate was 53%. Multivariate analysis identified four highly significant independent predictors of mortality; preoperative hypotension, intraperitoneal rupture, preoperative coagulopathy, and preoperative cardiac arrest. Using these inputs, the neural network correctly predicted outcome in 82.5% of individual cases.

CONCLUSION

a neural network based on just four perioperative variables can accurately predict outcome of RAAA. Prognostic variables should be reported in studies as a measure of the effect of case mix on survival data. Neural networks have potential to aid decision-making relating to outcome for individual cases.

Neural networks in the diagnosis of malignant ovarian tumours

OBJECTIVE

To assess the role of neural networks in predicting the likelihood of malignancy in women presenting with ovarian tumours.

DESIGN

Retrospective case study.

SETTING

University Department of Obstetrics and Gynaecology, St James's Hospital, Leeds.

METHODS

Information from 217 cases with histologically proven benign, borderline or malignant tumours was extracted for study. Four variables (age, ultrasound findings with and without colour Doppler imaging and CA125) were entered in the neural network classifier. The neural network results were compared with logistic regression analysis.

RESULTS

When used in the neural network the variables of age, CA125 and ultrasound score produced the best result with a sensitivity of 95% and a corresponding specificity of 78% in predicting malignancy. Logistic regression gave a sensitivity or 82% for a specificity of 51%.

CONCLUSION

The neural network is a good method of combining diagnostic variables and may be a useful predictor of malignancy in women presenting with ovarian tumours. A comparison of the performance of the neural network with conventional diagnostic methods would be warranted prior to use in clinical practice.

The application of neural networks in predicting the outcome of in-vitro fertilization

Infertility affects one in six couples at some time in their lives, with 48% of these couples requiring assisted conception techniques in order to achieve a pregnancy. Whilst the overall clinical pregnancy rate per embryo transfer is 23%, this varies widely between clinics. The Human Fertilisation and Embryology Authority has attempted to analyse the results of all units, with weighting of different factors affecting assisted conception, and the published data have invariably led to comparisons between units. However, statistical models need to be developed to eliminate bias for valid comparisons. Neural networks offer a novel approach to pattern recognition. In some instances neural networks can identify a wider range of associations than other statistical techniques due in part to their ability to recognize highly non-linear associations. It was hoped that a neural network approach may be able to predict success for individual couples about to undergo in-vitro fertilization (IVF) treatment. A neural network was constructed using the variables of age, number of eggs recovered, number of embryos transferred and whether there was embryo freezing. Overall the network managed to achieve an accuracy of 59%.

An expert system to assist neonatal intensive care

An expert system for neonatal intensive care (ESNIC) for the management of mechanically ventilated neonates on intermittent positive pressure ventilation (IPPV) has been developed. The system uses the rule based expert system shell XiPlus (Inference Inc.) and runs on an IBM-compatible PC. The rules have been derived from the knowledge of two consultant paediatricians. The inputs to the system are the current ventilator settings, blood gas tensions and pH. The output of the system is a set of suggested new ventilator settings. The aim of the system is to provide ventilator settings which will maintain the arterial blood gas tensions within an acceptable range, reducing pressures whenever feasible and increasing pressures only as a last resort. In addition, ESNIC provides data archiving, graphical displays of all parameters, ventilation and discharge summaries. With the 63 patients in the study ESNIC was consulted for 76% of all ventilator adjustments and the advice given was accepted on 83% of these occasions.

5-year follow-up of patients successfully transplanted after immunoadsorption to remove anti-HLA antibodies

The function of renal allografts in patients who had received pretransplant immunoadsorption in order to remove cytotoxic anti-HLA antibodies was studied. We reviewed 6 patients who received a graft which functioned beyond 3 months; the mean follow-up period was 76 (range 62-89) months. Two grafts have been lost from chronic rejection, at 12 and 62 months, respectively. The mean plasma creatinine levels at 1 and 5 years were 169 (range 143-211) mumol/l and 155 (range 92-235) mumol/l, respectively (1.91, range 1.62-2.39, mg/dl and 1.75, range 1.04-2.66 mg/dl, respectively). The major source of morbidity during long-term follow-up has been the occurrence of renal artery stenosis in 5 patient and renal vein stenosis in 1. In conclusion, the 5-year graft survival and function was good in patients who received immunoadsorption and whose grafts survived beyond the first 3 months after transplantation.

Reduction of gangrene and amputations in diabetic renal transplant patients: the role of a special foot clinic

This 4-year prospective study investigated the reasons for high levels of gangrene and major amputation in diabetic renal transplant patients and whether regular multidisciplinary foot care could reduce morbidity. All foot lesions were documented and investigated in 50 diabetic patients, mean age 49.2 +/- 11.0 (SD) years, duration of diabetes 25.3 +/- 9.0 years, time since renal transplantation 60.2 +/- 35.1 months, who attended a special foot clinic monthly for education, vascular and neurological assessment, podiatry and footwear. Foot lesions included: neuropathic ulcers, ischaemic ulcers, traumatic lesions, Charcot's arthropathy, pathological fracture. Treatment included antibiotics, podiatry, footwear, and angioplasty or distal bypass where appropriate. Only 13 patients were deemed ischaemic but peripheral neuropathy was a very common finding (mean VPT 24.8 +/- 12.9 V). Gangrene and major amputations showed a decrease on previous years and healing times for lesions were similar to those previously reported in diabetic patients without renal transplants. The majority of foot lesions, both in soft tissue and bone, were related to neuropathy and trauma and responded well to optimal foot care within the renal unit. Gangrene and major amputations were usually preventable.

To PEEP or not to PEEP?

It is well recognised that reducing positive end expiratory pressure (PEEP) leads to an increase in the tidal volume and minute volume in ventilated neonates. The magnitude of this effect is perhaps not commonly appreciated, however. Effectively, PEEP is four times as potent as peak inflation pressure (PIP) in bringing about changes in tidal volume. The influence of changes in PEEP and PIP on tidal volume and the relative magnitude of each are considered. Twenty one preterm infants were studied on 38 separate occasions. All were sedated, paralysed, and ventilated, 19 for hyaline membrane disease. A 1 cm H2O reduction in PEEP was twice as potent as a 2 cm H2O increase in PIP in achieving an increase in tidal volume (14 v 7%). Similarly, increasing PEEP by 1 cm H2O was twice as effective as a 2 cm H2O decrease in PIP in reducing tidal volume (13 v 6%). Small (0.5-1 cm H2O) changes in PEEP can often be used to improve ventilation and carbon dioxide elimination. Levels of PEEP of 4-5 cm H2O may, at times, impair gas exchange and contribute to overdistension.

An advisory system for artificial ventilation of the newborn utilizing a neural network

A neural network has been developed to manage ventilated neonates. The network inputs are the current ventilator settings (inspiratory and expiratory times, peak inspiratory and positive end-expiratory pressures and inspired oxygen concentration), partial pressures of arterial blood gases and pH. Two hidden layers comprising 50 nodes each are employed in the network, which utilizes a standard back-propagation algorithm. The network provides the new ventilator settings as five outputs that represent the most appropriate ventilator settings projected to maintain blood gases within an acceptable range. The network has been trained using a data set derived from a rule-based expert system developed for the same purpose. Performances of both systems have been compared. The neural network is capable of learning and adapting to the individual patient's response, which in principle offers significant advantages over the rule-based system.

Renal replacement for diabetic patients: experience at King's College Hospital 1980-1989

Renal failure is an important cause of morbidity and mortality in diabetic patients, who account for up to 25 per cent of new patients entering renal replacement therapy. Between 1980 and 1989, 651 patients with renal failure were treated at King's College Hospital, of whom 177 (27 per cent) had diabetes. Of these 177 patients 148 had diabetic nephropathy (65 non-insulin-dependent), while the rest had other renal diseases. Of the non-insulin-dependent diabetics, 45 per cent (29 of 65) were Asian or Afro-Caribbean compared to only 12 per cent (10/83) of the insulin-dependent diabetics. Ninety-two patients (62 per cent) have received a renal transplant with actuarial patient survival of 82 per cent at 1 year and 61 per cent at 4 years. Both patient and graft survival have been improved by the introduction of cyclosporin A. Continuous ambulatory peritoneal dialysis is the main form of dialysis and has allowed increasing numbers of patients to be dialysed, especially older individuals with non-insulin-dependent diabetes. Rehabilitation is best in those with functioning transplants: 21 patients (19 with functioning grafts) have survived for longer than 5 years. Diabetic complications before and after renal replacement therapy are described. Cardiovascular disease is especially common and may limit the success of renal replacement therapy.

Non-insulin-dependent diabetes and renal replacement therapy

Reports of renal replacement therapy in diabetes usually refer to patients with insulin-dependent diabetes mellitus (IDDM) only, and little is known about renal failure in non-insulin-dependent diabetics (NIDDM). A high proportion, 46/141 (32%), of the diabetics treated at our unit since 1974 had NIDDM. They were older at treatment (56 +/- 9 years, mean +/- SD) compared to the IDDM patients (39 +/- 10 years, p less than 0.001), and had a shorter duration of diabetes (13 +/- 8 years versus 23 +/- 8 years, p less than 0.001). Asians and Afro-Caribbeans accounted for 48% of the NIDDM patients (22/46) compared to only 7% of those having IDDM (6/95, p less than 0.0001). Non-diabetic renal disease accounted for the renal failure in 32% (15/46) of the NIDDM patients but only in 10.5% (10/95) of the IDDMs (p less than 0.001). Despite these differences the prevalence of other diabetic complications (retinopathy, neuropathy, and cardiovascular disease) was similar. Patient survival after transplantation was poorer in NIDDM than IDDM (23% and 57%, respectively, at 2 years). Survival on dialysis was equally poor in NIDDM and IDDM. Thus, NIDDM patients treated for renal failure are more commonly non-European and more often have non-diabetic renal disease. Yet other diabetic complications occur to the same extent in both IDDM and NIDDM patients with diabetic nephropathy.

Diabetic pregnancy following renal transplantation

Renal transplantation for diabetic nephropathy prolongs survival and the return of fertility makes pregnancy possible. We describe a successful pregnancy in a 38-year-old diabetic renal transplant recipient despite blindness, gangrenous toes, cardiac impairment, and both sensory and autonomic neuropathy. Renal function remained stable throughout the pregnancy which was complicated by supine hypertension, postural hypotension and increasing proteinuria. Fetal distress and increasing proteinuria precipitated delivery by Caesarean section at 29 weeks of a female infant weighting 1.1 kg. Following delivery, hypertension improved, gangrene resolved, proteinuria decreased, and renal function remained stable. Pregnancy in long-standing diabetic patients with renal transplants, although hazardous, may be successful yet the maternal morbidity and mortality makes them inadvisable.

Isolation of Clostridium botulinum from Honey

Methods for the isolation of Clostridium botulinum from honey samples are described. A total of 9 of 90 honey samples were positive for C. botulinum; 6 of the positive samples had been fed to babies who developed infant botulism.

Changes in lung capillary permeability in renal failure

Excess fluid in the lung can be quantified in chronic dialysis patients by using the double indicator dilution technique. The lung capillaries show an increased permeability to sodium when these patents develop pulmonary oedema.