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Biomedical subjects

J S Curnow

Publications and source records attributed to J S Curnow.

9 recordsLinked to original sources
PubMed1995

Four channel foetal ECG data collection system.

Recently there has been an increased interest in the development of improved techniques for the diagnosis of foetal distress during labour. Many of the techniques have been based on extracting extra information from the foetal ECG obtained from a scalp electrode. To fully develop and test the prototypes of these systems requires recorded data from patients. However due to the poor level of prediction of these cases at present, it is very difficult to collect the data using simple single channel data collection systems. The system described here will automatically collect and document data from up to four deliveries at the same time and does not add to the work load of the clinical staff.

Biomedical Engineering↗
PubMed1992

Randomised trial of cardiotocography alone or with ST waveform analysis for intrapartum monitoring.

It is possible to record the fetal electrocardiographic waveform (ECG) from the scalp electrode used in labour for detection of fetal heart rate. Animal and observational studies of changes in the ST waveform of the ECG during hypoxia suggest that a combination of heart rate and ST waveform analysis might improve the predictive value of intrapartum monitoring. In a randomised trial, we have studied intervention rates and neonatal outcome for high-risk labours monitored either by conventional cardiotocography (CTG) or by ST waveform analysis plus CTG. 1200 women with pregnancy of at least 34 weeks' gestation were assigned to the groups when the decision to apply a fetal scalp electrode was made. Neonatal outcome was assessed by umbilical-cord blood gas analysis, Apgar scores, resuscitation needed, and postnatal course. All recordings were retrospectively viewed by an observer unaware of clinical details to check adherence to the trial protocol. The addition of ST waveform monitoring to CTG substantially reduced the proportion of deliveries for fetal distress (ST + CTG 27/615 vs CTG 58/606; p less than 0.001). The groups did not differ in rate of operative delivery for other reasons, incidence of asphyxia at birth, or neonatal outcome. Metabolic acidosis and low 5 min Apgar scores were less common in the ST + CTG than the CTG group, but not significantly so. The only case of birth asphyxia in the ST + CTG group was identified by both heart rate and ST changes. The review of recordings showed that the reduction in intervention rate was among cases with CTG patterns classified as normal or intermediate, whereas there was no difference in intervention rates among cases with abnormal recordings. Our findings confirm that ST waveform analysis discriminates CTG changes in labour and that our protocol for interpretation is safe. Further randomised studies are warranted.

Adult↗
PubMed1990

Suitability of fetal scalp electrodes for monitoring the fetal electrocardiogram during labour.

As the limitations of heart-rate based intrapartum monitoring have become apparent, there is renewed interest in analysis of the fetal electrocardiographic waveform as obtained from a fetal scalp electrode. A high quality ECG signal is necessary for waveform analysis. This study examined the suitability of five commonly available scalp electrodes for collecting this signal by examining their physical and electrical characteristics, together with a randomised clinical trial in which the ECG trace quality was assessed in 50 patients. The frequency response of Copeland electrodes was such that they attenuate the ECG signal more than the baseline noise. Difficulties were experienced in obtaining optimum attachment and the long, semi-rigid design increased movement artefact resulting in significantly poorer quality ECG signals. Whilst the Hewlett-Packard double spiral electrode had a near ideal frequency response, certain design features made it difficult to apply and remain secure so the clinical signals were of intermediate quality. The Corometrics and Cetro single spirals had the most stable attachment to the scalp and a near ideal frequency response, so produced significantly better signal quality in the clinical trial. Currently, single spiral electrodes are the most suitable for electrocardiographic data collection.

Electrocardiography↗
PubMed1985

The ventilatory response to carbon dioxide. An analysis of data obtained by the rebreathing method.

The ventilatory response to carbon dioxide using the rebreathing method was studied repeatedly in four healthy volunteers. The data were collected and processed in different ways using a microcomputer. Least squares linear regression analysis described the responses almost as accurately as a non-linear second-order polynomial regression. Linear regression analysis was undertaken on VI/PE'CO2 points, first breath-by-breath and then on three different groupings of breaths. The gradients and intercepts obtained by grouping agreed with those from breath-by-breath analysis both for a single response and for the mean result of a number of responses. Grouping tended to increase the correlation coefficient of a response, but widened the statistical confidence limits of the calculated gradient. The performance variability between repeated responses, the same no matter which data points were used, produced a range of gradients for each subject which was larger than the confidence limits on the gradient of a single response.

Adult↗
PubMed1984

Effect of rebreathing on psychomotor skills when wearing integral crash helmets.

Nine volunteer subjects underwent psychomotor testing when wearing an integral crash helmet in a variety of conditions which lead to rebreathing. There was a wide individual variation in the extent of rebreathing. In the worst conditions the minimum inspired carbon dioxide tension (PICO2) increased to 2.6 kPa. The psychomotor test was a tracking test based on a microcomputer. There was a significant deterioration in the ability to perform the test when the helmet was worn with the visor down and restricted airflow into the helmet (P = less than 0.05). In those tests when the minimum PICO2 exceeded 0.5 kPa the decrease in performance was more highly statistically significant (p = less than 0.005). Rebreathing wearing integral crash helmets results in a variable impairment in the subjects' ability to perform a tracking test. We recommend that the maximum level of CO2 retention inside integral crash helmets should not exceed 0.5 kPa minimum PICO2.

Carbon Dioxide↗
PubMed1981

Infusions of minaxolone to supplement nitrous oxide-oxygen anaesthesia. A comparison with althesin.

In 19 patients, minaxolone citrate, a water-soluble steroid anaesthetic agent, has been used as a continuous infusion to supplement nitrous oxide anaesthesia. The minimum infusion rate (MIR) was found to be 11.3 micrograms kg-1 min-1 for patients premedicated with morphine 10 mg i.m. and breathing spontaneously 66% nitrous oxide in oxygen. The cardiovascular and respiratory effects were similar to those described in a previous study for Althesin administered under comparable conditions. Recovery from minaxolone was prolonged compared with Althesin, and this may be related both to the water-solubility of the drug, and to its greater apparent volume of distribution.

Adult↗