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.

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.

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.

A comprehensive on-line computerised lung function screening test.

An on-line computerised lung function screening test is described which prints out 22 lung function parameters and a functional diagnosis. The complete test with print-out data takes less than 8 min per patient which implies that more than 60 out-patients can be 'screened' per day. Furthermore, for patients about to undergo major surgery a lung function operative risk grading is also available. The developed computer system is comparatively inexpensive, simple to operate and can be immediately on-lined to most apparatus without special interfacing. The total screening system can be operated by a single technologist and the required respiratory manoeuvres can be performed by almost all patients irrespective of the degree of lung function impairment. Although comprehensive in itself the screening test has been invaluable in deciding upon which patients require more intensive and time-consuming lung function investigations.

A new lung function index: the area under the maximum expiratory flow-volume curve.

A new lung function index, the area under the maximum expiratory flow-volume curve (AFVx) is described. A predicted AFVx based on age, sex and height is determined, and the measured to predicted AFVx ratio is assessed by comparison with other established lung function parameters. This ratio appears to be a very sensitive indicator of the degree of lung function impariment.