Comparison between a newly developed PC-based Doppler umbilical artery waveform analyser and a commercial unit.

OBJECTIVES: To determine the accuracy of the resistance index (RI) of flow velocity waveforms of the umbilical artery measured using a newly developed PC-based continuous wave Doppler device (Umbiflow) with regard to systematic and random variations when compared with a commercial standard (Vasoflow). DESIGN: A cohort study. SETTING: The fetal evaluation clinic (FEC) at Tygerberg Hospital. SUBJECTS: Patients referred to the FEC at Tygerberg Hospital with suspected chronic placental insufficiency. OUTCOME MEASURES: The correlation coefficients indicating the strength of the relationship between the two devices and their agreement using the method of Bland and Altman. RESULTS: A total of 248 patients were studied. The mean RIs of the first Doppler assessment were 0.69 (standard deviation (SD) 0.11) and 0.67 (SD 0.11) using the Vasoflow and Umbiflow respectively. The Pearson's correlation coefficient comparing the RI of the first test was 0.85. The degree of agreement between the two methods was excellent, the mean differences being very small (< 0.024) with tight confidence intervals. One hundred and ninety-four patients (78.2%) of patients remained in the same percentile category with both the Vasoflow and Umbiflow. CONCLUSIONS: The accuracy of the Umbiflow has been proved. A non-significant trend towards slightly lower values needs to be considered. This could be addressed by changing the percentile cut-off to slightly lower values.

Falciparum malaria in malaria-naive travellers and African visitors.

BACKGROUND: Patients from malaria-endemic areas who present in non-endemic countries with Plasmodium falciparum malaria are often assumed to have some degree of immunity. If this were reliably true, it would simplify their management. AIM: To determine whether being born and resident in a malaria-endemic country is a predictor of clinical course in UK admissions for malaria. DESIGN: Prospective observational study. METHODS: We compared clinical and laboratory parameters between two groups of adult patients with acute P. falciparum malaria, admitted to the Hospital for Tropical Diseases in London: one born and resident in non-endemic countries (n=167); the other born and resident in malaria-endemic countries of Africa (n=93). Patients were excluded if they had taken prophylaxis or prior treatment. RESULTS: There were no differences between these two groups in terms of peak parasitaemia or time to parasite clearance. There was a significantly higher risk of malaria-naive patients having peak parasitaemia >5% (OR 4.5, 95%CI 1.5-13.2). Of those usually resident in Africa, 31% required parenteral treatment compared to 41% of the malaria-naive group. Of the visitors from Africa, 4.3% needed admission to the Intensive Therapy Unit (ITU), although there was a tendency for more malaria-naive patients to require ITU care (OR 2.69, 95%CI 0.9-8.1). DISCUSSION: While there are differences in presentation between those who are malaria-naive and those who live in malaria-endemic African countries, making assumptions about the immunity or clinical course of an individual patient with malaria presenting in the UK on the basis of presumed history of exposure is unwise.

Polymorph count for predicting non-gonococcal urethral infection: a model using Chlamydia trachomatis diagnosed by ligase chain reaction.

BACKGROUND/OBJECTIVES: The criteria for the diagnosis of non-gonococcal urethritis (NGU) on a Gram stained urethral smear are derived from previous studies which used culture as a diagnostic test for Chlamydia trachomatis. Our objectives were (1). to re-assess the relation between urethral polymorph count and C trachomatis infection, using ligase chain reaction (LCR) as the diagnostic test; and (2). to assess other possible predictors of C trachomatis infection such as symptoms, signs, demographic and behavioural variables. METHODS: We collected data from 363 men consecutively attending a genitourinary medicine clinic (excluding those with gonorrhoea and follow up visits) who had a urethral smear and a urethral LCR test for C trachomatis. The sensitivity and specificity of a discrete cut off in urethral polymorphonuclear leucocyte (PMNL) count as a diagnostic test for chlamydia urethritis were calculated. The associations between other variables, such as age and symptoms, and this infection were also estimated. RESULTS: 8% of men had C trachomatis infection and 26% of men had a PMNL count of 5 or more. Of those men with chlamydia 37% did not have NGU; 20% of men with NGU had chlamydia. Adjusted odds ratios for risk of chlamydial infection were significant for age less than 30 relative to 40 years and over (adj OR 13.6; 95% confidence interval 1.69 to 110), a PMNL count of 20 or more (6.56; 2.15 to 20.0), a PMNL count of 5-19 (3.59; 1.41 to 9.15), and the symptom of dysuria (3.27; 1.32 to 8.08). However a PMNL count of 5 or more was only 63% sensitive and 77% specific for C trachomatis infection. No association between sexual behaviour and chlamydial infection was found in this setting. CONCLUSIONS: The PMNL count is associated with presence of chlamydial infection but a large proportion of men with chlamydia have PMNL counts below the recommended cut off for a diagnosis of NSU. Lower age and the presence of symptoms may be as predictive as the urethral polymorph count for chlamydial urethritis and possibly for other urethral infections.

Childhood adversity, parental vulnerability and disorder: examining inter-generational transmission of risk.

BACKGROUND: An investigation of intergenerational factors associated with psychiatric disorder in late adolescence/early adulthood was undertaken to differentiate influences from maternal disorder, maternal poor psychosocial functioning and poor parenting, on offspring. METHOD: The sample comprised an intensively studied series of 276 mother-offspring pairs in a relatively deprived inner-city London area with high rates of lone parenthood and socio-economic disadvantage. The paired sample was collected over two time periods: first a consecutively screened series of mothers and offspring in 1985-90 (n = 172 pairs) and second a 'vulnerable' series of mothers and offspring in 1995-99 (n = 104 pairs). The vulnerable mothers were selected for poor interpersonal functioning and/or low self-esteem and the consecutive series were used for comparison. Rates of childhood adversity and disorder in the offspring were examined in the two groups. Maternal characteristics including psychosocial vulnerability and depression were then examined in relation to risk transmission. RESULTS: Offspring of vulnerable mothers had a fourfold higher rate of yearly disorder than those in the comparison series (43% vs. 11%, p < .001). They were twice as likely as those in the comparison series to have experienced childhood adversity comprising either severe neglect, physical or sexual abuse before age 17. Physical abuse, in particular, perpetrated either by mother or father/surrogate father was significantly raised in the vulnerable group. Analysis of the combined series showed that maternal vulnerability and neglect/abuse of offspring provided the best model for offspring disorder. Maternal history of depression had no direct effect on offspring disorder; its effects were entirely mediated by offspring neglect/abuse. Maternal childhood adversity also had no direct effect. CONCLUSIONS: Results are discussed in relation to psychosocial models of risk transmission for disorder. Maternal poor psychosocial functioning needs to be identified as a factor requiring intervention in order to stem escalation of risk across generations.

Technology in health care--blessing or curse?

This paper looks at technology and health care in terms of processes (here defined as goal-related, autonomous and self-regulated arrangement of actions) and their interactions. Using this approach, technology is considered to be the quality of the processes we are trying to achieve. However, health care and the life around it is a complex network of closely interacting processes, and through their interactions, processes can influence each other in various ways. In many cases such interactions can result in unwanted, inappropriate interference and the implementation of unsatisfactory health care technologies.

Randomised evaluation of a prototype suction fetal scalp electrode.

OBJECTIVE: To compare the performance and acceptability of a prototype suction fetal scalp electrode with that of a double helix spiral electrode. SETTING: An urban academic hospital in Johannesburg, South Africa. DESIGN: Randomised, by means of sealed opaque envelopes opened consecutively. PARTICIPANTS: One hundred women in active labour with an indication for direct fetal heart rate monitoring. INTERVENTION: Application of a fetal scalp electrode to the presenting part. OUTCOME MEASURES: Performance of the electrodes with respect to application success, detachment, quality of the tracings, scalp trauma and women's preferences. RESULTS: Application of the suction electrode was unsuccessful in 15/50 (30%) compared to 1/50 (2%) with the spiral electrode. Detachment rates were similar. There were more tracings of average quality with the suction electrode (nine versus four). There were three instances of scalp bleeding at delivery with the spiral electrode. The suction electrode was preferred by more women and its application caused somewhat less discomfort. CONCLUSIONS: The lower rate of successful application with the suction electrode needs to be weighed against the advantage of avoiding fetal scalp penetration. In particular, women's concerns about pain or harm to the baby from needle electrodes, the theoretical risk of viral transmission, and the risk of serious scalp infection must be considered. These factors favour the use of a suction electrode when direct fetal heart rate monitoring is required. Needle electrodes should be considered when suction electrode application is unsuccessful. Correction of practical problems experienced with the prototype suction electrodes used in this study may result in improved success rates.

Transport behavior of groundwater protozoa and protozoan-sized microspheres in sandy aquifer sediments.

Transport behaviors of unidentified flagellated protozoa (flagellates) and flagellate-sized carboxylated microspheres in sandy, organically contaminated aquifer sediments were investigated in a small-scale (1 to 4-m travel distance) natural-gradient tracer test on Cape Cod and in flow-through columns packed with sieved (0.5-to 1.0-mm grain size) aquifer sediments. The minute (average in situ cell size, 2 to 3 (mu)m) flagellates, which are relatively abundant in the Cape Cod aquifer, were isolated from core samples, grown in a grass extract medium, labeled with hydroethidine (a vital eukaryotic stain), and coinjected into aquifer sediments along with bromide, a conservative tracer. The 2-(mu)m flagellates appeared to be near the optimal size for transport, judging from flowthrough column experiments involving a polydispersed (0.7 to 6.2 (mu)m in diameter) suspension of carboxylated microspheres. However, immobilization within the aquifer sediments accounted for a log unit reduction over the first meter of travel compared with a log unit reduction over the first 10 m of travel for indigenous, free-living groundwater bacteria in earlier tests. High rates of flagellate immobilization in the presence of aquifer sediments also was observed in the laboratory. However, immobilization rates for the laboratory-grown flagellates (initially 4 to 5 (mu)m) injected into the aquifer were not constant and decreased noticeably with increasing time and distance of travel. The decrease in propensity for grain surfaces was accompanied by a decrease in cell size, as the flagellates presumably readapted to aquifer conditions. Retardation and apparent dispersion were generally at least twofold greater than those observed earlier for indigenous groundwater bacteria but were much closer to those observed for highly surface active carboxylated latex microspheres. Field and laboratory results suggest that 2-(mu)m carboxylated microspheres may be useful as analogs in investigating several abiotic aspects of flagellate transport behavior in groundwater.

A nonpenetrating fetal scalp electrode.

OBJECTIVE: To develop a nonpenetrating scalp electrode for intrapartum fetal monitoring. DESIGN: Preliminary observational evaluation of the device. SETTING: An urban academic hospital in Johannesburg, South Africa. SUBJECTS: Fifteen women in labour. INTERVENTION: Application of the electrode for intrapartum monitoring. OUTCOME MEASURES: Quality of tracings, duration of application, disconnection of the electrode, marking of the scalp. RESULTS: Application was successful in 13 of 15 women, and high quality tracings obtained in 12. CONCLUSIONS: The design of scalp electrode tested is effective and produces high quality tracings in most cases.

PIP: The fetal scalp electrodes currently used to obtain fetal heart rate (FHR) recordings during labor employ single or double curved needles which penetrates the fetal skin to obtain a purchase and electrical contact. A nonpenetrating scalp electrode was designed whose application to the fetal scalp is maintained by means of suction. The nickel fetal plate of the electrode measures 16 mm in diameter and has multiple perforations to distribute the effect of the suction and maintain optimal electrical contact over its whole surface. The electrode has an overall diameter of 20 mm and can be applied to the presenting part from 2-3 cm cervical dilatation. Application of the electrode was attempted in 15 consecutive pregnancies. Of the 15 consecutive attempts, 13 were successful. Unsuccessful attempts were caused by a blocked suction tube following repeated resterilization and reuse of the electrode in one instance and failure to position the electrode correctly in an excessively anxious woman in another. The quality of FHR tracing in 12 was considered good, providing continuous recording with minimal interference, while, in 1 woman, the tracing was poor. Good quality tracings were obtained even when the electrode was applied over thick hair, in the presence of vernix caseosa, and, in 1 application, to the buttocks. In 9 applications, the tracing started immediately after application, and, in the rest, there was a lag period of 2-20 minutes before the tracing commenced. A subsequent modification to a more finely apertured stainless steel mesh electrode plate eliminated the problem of a lag phase. In 1 instance, the electrode was disconnected during examination; in 2 cases, it was detached 10 minutes and 1 minute before delivery, respectively; and, in 10 cases, it remained in place until delivery. Transient redness of the fetal scalp was noted in 6 babies, and, in 2 babies, fine vesicles were noticed which disappeared within 2-3 days. This problem may be avoidable by using less suction pressure.

Assessing malnutrition in gastric carcinoma: bioelectrical impedance or clinical impression?

The value of bioelectrical impedance (BI) as an index of body composition was assessed in 32 patients with gastric carcinoma, 20 with advanced disease. Bioelectrical impedance was compared with standard nutritional parameters: weight, body mass index (BMI), albumin, transferrin and triceps skinfold thickness. There was no correlation between BI and these parameters with the exception of weight and BMI in the male patients. Clinical assessment of nutrition on the other hand correlated well with the standard parameters. Although BI may be a useful adjunct to the routine assessment of nutritional status in normal subjects, its use in clinical patients should be treated with caution, particularly in those with advanced gastrointestinal malignancy.

The estimation of tube wall compliance using acoustic input impedance.

An acoustic-electric analog and transmission line theory have been used to examine acoustic wave propagation in a tube with a compliant wall. The input impedance (i.e., input pressure-flow) has been simulated using a distributed element model. A relative minimum and maximum, denoted by fr and f2, respectively, that are independent of tube length have been identified theoretically and confirmed experimentally from input impedance measurements on a compliant tube. A method has been devised which uses measured values of fr and f2 to deduce the tube wall properties from the theoretical model. This method has been validated on a tube with known wall properties determined using standard methods. In practice, the input impedance is measured through a short section of rigid connecting pipe. In this case fr remains constant while f2 is reduced. This reduction can be accounted for by the volume compliance of the gas within the lumen of the rigid pipe. The theory could have useful applications such as estimating the wall properties of the airways from noninvasive measurements made through the mouth.

Cross-section study of pulmonary function in patients with insulin-dependent diabetes mellitus.

In this study, we attempted to establish the prevalence and nature of pulmonary dysfunction in a cross section of a diabetic population and the relationship of pulmonary dysfunction to diabetic factors and complications. Forty insulin-dependent diabetic patients, 15 to 60 yr of age, and 40 healthy reference subjects, matched for age, sex, and race, were studied. All subjects were lifelong nonsmokers and had no clinical evidence of past or present respiratory disease. Lung function was assessed from the flow-volume curve, single-breath nitrogen washout, static lung elastic recoil, and pulmonary diffusing capacity (DLCO/VA) and its components: membrane diffusing capacity (Dm/VA) and pulmonary capillary blood volume (Qc/VA). The diabetic patients had an increased value for Kst(L) and in Kst(L), the exponential shape constant of the pressure-volume curve compared with that of the reference subjects (Kst(L), 0.184 +/- 0.011 versus 0.135 +/- 0.005; p less than 0.005, mean +/- SEM). The DL/VA was lower in the diabetic subjects (4.62 = 0.12 versus 5.31 +/- 0.10 ml/min/mm Hg/L; p less than 0.001), and this was due to a lower Qc/VA (9.45 +/- 0.43 versus 11.75 +/- 0.35 ml/min; p less than 0.001). The Kst(L) and Qc/VA were correlated with the duration of diabetes. The In Kst(L) was negatively correlated with both DL/VA (r = -0.32, p less than 0.05) and Qc/VA (r = -0.36, p less than 0.05). There was no association between abnormal pulmonary function and the presence of other diabetic complications. It is concluded that there are mild, duration-related abnormalities of lung elastic recoil and pulmonary diffusing capacity and a reduction in pulmonary capillary blood volume in insulin-dependent diabetes mellitus.

Pulmonary function in young insulin-dependent diabetic subjects.

To clarify the issue of pulmonary dysfunction in diabetes mellitus, lung mechanics and CO transfer were investigated in 22 young (mean age 19.5 +/- 5 years) non-smoking, insulin-dependent diabetic patients and an equal number of matched healthy subjects. Mean closing capacity/total lung capacity (CC/TLC) was significantly greater in the diabetic than in the control group (31.4 +/- 6.8 vs 27.2 +/- 2.9 percent, p less than 0.01), as was the mean value of the volume independent index of lung elasticity (exponent constant, Kst(L)) (0.148 +/- 0.045 vs 0.118 +/- 0.030, p less than 0.05). The transfer factor expressed per unit alveolar volume (TL/VA) was also significantly lower in the diabetic than in the control group (5.25 +/- 0.68 vs 5.61 +/- 0.57 ml/min/mm Hg/L, p less than 0.05) and this could be ascribed to a lower pulmonary capillary blood volume. There was evidence of mildly abnormal lung mechanics and/or a decreased pulmonary capillary blood volume in 16 (73 percent) of the diabetic group. Since pulmonary dysfunction was either an isolated non-endocrine finding or was associated with only early systemic complications in these young patients, our findings suggest that pulmonary dysfunction is an early measurable complication in insulin-dependent diabetes mellitus.

Interaction of verapamil hydrochloride and atropine sulphate on histamine-induced bronchoconstriction.

Submaximal histamine dose-response curves were obtained on 34 dogs divided into six groups. These groups were: A (n = 6) untreated; B (n = 6) after atropine (1 mg/kg); C (n = 5) after verapamil inhalation (10 mg total dose); D (n = 5) after verapamil inhalation (100 mg total dose); E and F (n = 6) as for C and D but pre-treated with atropine (1 mg/kg). Total lung resistance (R1) was measured in each case at increasing delivered concentrations of inhaled histamine and expressed as a ratio of baseline valve. For each group a composite mean curve was obtained and the maximal recorded responses (mean maximal resistance ratios) for the various groups were compared. It appears that the combination of verapamil inhalation (low dose) and atropine reduced the anticholinergic effect of atropine causing marked bronchoconstriction. This unexpected result depends on the verapamil dose since it was not present at the higher dose (group F).

A mechanism for stimulated acoustic emissions in the cochlea.

Stimulated acoustic emissions in the cochlea are explained in terms of its hydraulic properties. The mathematical model predicts that these 'echoes' are caused by reflections which result from a discontinuity in the resistive and reactive components of the impedance which occurs at resonance. This discontinuity is a direct result of the wavelength-dependent nature of the fluid inertance and occurs without the consideration of non-linearities. Calculations of the time delay of tone bursts to and from the places of reflection by determination of the group velocity agree with observations of the response latencies for the frequencies concerned.

Different, dose-dependent effects of verapamil inhalation on histamine-induced bronchoconstriction in anaesthetized dogs.

Different, dose-dependent effects of verapamil inhalation on histamine-induced bronchoconstriction in anaesthetized dogs are reported. Cumulative histamine dose-response curves were obtained on three groups each consisting of six dogs. These groups were: A - after atropine sulphate (1 mg/kg); B - after atropine sulphate and verapamil (approximately 0.5 mg/kg); C - after atropine sulphate and verapamil (approximately 5.0 mg/kg). Total lung resistance (R1) was measured as the indicator of bronchoconstriction. The mean maximal response of R1 in B was significant greater (p less than 0.01) than in A and C, while no significant difference was observed between A and C. A possible mechanism is postulated.