The repeatability of cerebral autoregulation assessment using sinusoidal lower body negative pressure.

A forced periodic variation in blood pressure produces a similar variation in cerebral blood velocity. The amplitudes and phases of the pressure and velocity waveforms are indicative of the dynamic response of the cerebral autoregulation. The phase of the velocity leads the pressure; the greater the phase difference the faster the autoregulation response. Various techniques have been employed to oscillate arterial blood pressure but measurement reproducibility has been poor. The purpose of this study was to assess the reproducibility of phase measurements when sinusoidal lower body negative pressure is used to vary blood pressure. Five healthy volunteers were assessed at two vacuum levels on each of eight visits. For each measurement a 12 s sinusoidal cycle was maintained for 5 min. The Fourier components of blood pressure and the middle cerebral artery velocity were determined at the oscillation frequency. The phase of velocity consistently led the pressure. The mean phase difference was 42+/-13 degrees for the stronger vacuum and 36+/-42 degrees for the weaker vacuum. The variation given is the within-subjects standard deviation estimated from a one-way analysis of variance. Sinusoidal lower body negative pressure is a useful stimulus for investigating autoregulation; it has advantages over other methods. High vacuums show good reproducibility but are too uncomfortable for patient use.

An investigation of the diagnostic value of bilateral femoral neck bone mineral density measurements.

This paper describes a study to assess the clinical value of bilateral femoral neck bone mineral density (BMD) measurements. Although a range of factors will determine clinical decisions, the classification of the site with the lowest T-score is likely to have significant bearing on the management of a patient. While it is common practice to measure BMD at the lumbar spine and a single neck of femur, knowledge of the BMD of the second femur may also be of diagnostic value. Using dual-energy X-ray absorptiometry, BMD of the lumbar spine and right and left femoral neck was measured in a group of 2372 white, Caucasian women (mean age +/- SD, 56.6 +/- 13.9 years) routinely referred for bone densitometry. Analysis of the measurements showed a significant (p = 0.02) but small difference between the mean BMD of the right (0.840 +/- 0.152 g/cm2) and left (0.837 +/- 0.150 g/cm2) femoral neck. Further investigation of femur scans revealed 79 (3.3%) patients in whom one side was osteoporotic while the other side and spine were normal or osteopenic using the World Health Organization diagnostic criteria in combination with manufacturer's reference data. Patients in whom the femoral neck BMD measurements differed by less than the precision error of the system were then excluded. This left only 51 (2.2%) patients, that is 29 (1.2%) for right femur and spine scan and 22 (0.9%) for left femur and spine scan, in whom knowledge of both femoral neck BMD measurements could have altered the classification of the lowest site assessed to osteoporotic. These data suggest that there is only a small benefit from performing bilateral femoral neck BMD measurements. Since BMD measurements are only one of a range of factors considered as part of a patient's management, it is suggested that the extra time, cost and radiation dose associated with measurement of the second femur may not be justified.

Effect of inhaled corticosteroids on bone mineral density in childhood asthma: comparison of fluticasone propionate with beclomethasone dipropionate.

There is a dearth of data on long-term effects of inhaled corticosteroids (ICS) on bone architecture in childhood asthma. This study was designed to assess the possible effects of two different inhaled steroids on bone mineral density (BMD) in steroid-naïve, prepubertal children. Twenty-three children were randomized to receive equipotent doses of either fluticasone propionate (100 micrograms twice daily) or beclomethasone dipropionate (200 micrograms twice daily). They were followed up over a period of 20 months with regular dual-energy X-ray absorptiometry scans for BMD. Densitometry of lumbar spine and total body showed a significant increase over time, which followed the normal patterns for growth. No difference was observed between the two subgroups. There was no change in fat distribution over time and no increase in percentage total body fat. As expected, girls had significantly higher total body fat. This absence of deleterious effects suggests that in the standard doses used neither beclomethasone nor fluticasone has any significant effect on bone density over a moderate period of time. Further studies should continue monitoring BMD through the critical years of bone mass accumulation during adolescence.

Reference ranges of bone mineral density for women in southern England: the impact of local data on the diagnosis of osteoporosis.

The construction of reference ranges that accurately represent the population at large is essential for the correct identification of osteoporosis from bone mineral density (BMD) measurements. In this study, reference data supplied by the manufacturer of the Lunar DPX+ bone densitometer were compared with data obtained locally. Lumbar spine, proximal femur and total body BMD measurements were made in an age-stratified random sample of 702 Southampton women aged 20 to 89 years. Relevant demographic and medical data were recorded for each subject using a questionnaire. Reference curves of BMD (mean +/- SD) were plotted against age for each measurement site and were found to be higher than the manufacturer's reference values at all ages and sites. Exclusion of women with factors known to affect bone mass only served to increase this discrepancy. According to World Health Organisation definitions, osteoporosis may be identified from BMD values alone. Based upon neck of femur BMD values, 100 (14.8%) of the women in this study group were categorized as osteoporotic using local young normal reference data, compared with only 39 (5.8%) using the manufacturer's data. By normalizing for age distribution, these findings were extrapolated to the local population where it was predicted that 26.0% and 10.1% of females over 50 years of age would be classified as osteoporotic using the respective reference ranges. This study clearly illustrates how the numbers of women diagnosed as osteoporotic vary with the use of different reference populations.

Screening for fetal distress in labour using the umbilical artery blood velocity waveform.

OBJECTIVE: To investigate the potential value of umbilical artery blood velocity wave-form measurement as a screening test for intrapartum fetal distress on admission to the labour ward. DESIGN: Prospective study drawn from the local population of pregnant women. SETTING: The labour ward of the Princess Anne Hospital, Southampton, UK. SUBJECTS: 334 women with singleton pregnancies of at least 37 weeks gestation. MAIN OUTCOME MEASURE: Emergency caesarean section for fetal distress. RESULTS: There was a twelve-fold increase in the rate of emergency caesarean section for fetal distress (95% Confidence Interval (CI), 4.9-29) among women with a systolic/diastolic (S/D) ratio > or = 3.0, when compared to those with an S/D ratio of < 3.0 (P < 0.00001). Measurement of the umbilical artery blood velocity waveform compared favourably with admission cardiotocography. CONCLUSIONS: Umbilical artery blood velocity waveform analysis may be used to screen for fetal distress in labour and appears to be particularly sensitive to problems of placental origin. However, it is not likely to confer benefit in labour wards whose fetal heart rate monitoring policy is determined by pregnancy risk factors and admission cardiotocography.

Influence of Doppler ultrasound on fetal activity.

A randomised and double blind study of 100 subjects and 50 controls was performed to confirm or refute a report from Cardiff in 1975 that continuous Doppler ultrasound, as used in fetal heart rate monitoring, increases fetal movement by over 90%. The results showed such an effect to be most unlikely (power greater than 0.99). A total of 150 pregnant mothers recorded fetal movements for 30 minutes while connected to a specially modified cardiotocograph, the ultrasound being switched on at random for either the first or second 15 minutes in 100 of the patients. The mean difference in 15 minute movement count, with and without ultrasound, among the 100 patients was 0.2 of a movement (SD 12.7; p greater than 0.6 by two tailed Wilcoxon matched pairs signed ranks test). The control group showed a mean difference of 2.6 movements (SD 12.1; p greater than 0.2). Results of a pilot study suggested that the observations in the earlier report may have been influenced by mechanisms unrelated to ultrasound.

Changes in the fetal heart rate associated with fetal breathing and fetal movement.

Thirty-eight recordings of fetal heart rate and fetal activity were made from 21 normal patients between 36 and 41 weeks gestation. Each recording lasted for an average of 39 minutes. The heart rate was measured from beat to beat using the R-wave of the fetal electrocardiogram as the indicator of each heart-beat. Fetal breathing movements and fetal body movements were detected using either A-mode or B-mode ultrasound systems. The relation of fetal breathing and fetal movement to the fetal heart rate was studied both by cardiotachography and computer analysis of the R--R intervals. Fetal body movements (kicking and rolling) were usually associated with a brief tachycardia, the latter typically occurring every two to three minutes. In 14 recordings, the periods of fetal activity were interrupted by periods of fetal rest with an average duration of 12.5 minutes. Fetal breathing was seen in 26 of the 34 recordings analysed and occurred principally during the periods of fetal activity. Fetal breathing was associated with a significant increase in heart rate variation measured as the standard deviation of the R--R intervals and the mean absolute R--R interval difference. Sometimes a pattern of respiratory sinus arrhythmia was seen.

Actual practice of ECT in a health region of Britain.

A field study of 14 treatment centres found broad agreement between clinical practice and the Royal College of Psychiatrists' Memorandum on the use of ECT. Differences in electrode placement and anaesthetic agents and a poor standard of safety and reliability in the electrical equipment was noted.

Relation between volume swallowed and velocity of the bolus ejected from the pharynx into the esophagus.

The velocity of the front face of a liquid saline bolus ejected from the pharynx into the esophagus was measured by recording changes of luminal electrical impedance with three sets of electrodes in 9 subjects. At a site 26 cm from the incisors, the mean velocity of the front face of the bolus increased from 10 to 70 cm sec-1 as the volume swallowed was raised from 5 to 30 ml. The velocity of the front face of the bolus was greater 26 cm from the incisors than it was 32 cm from the incisors.