A data-based method for bivariate outlier detection: application to automatic blood pressure recording devices

Measuring arterial blood pressure in humans: Auscultatory and automatic measurement techniques for human biological field studies

Human biologists have been examining arterial blood pressure since they began studying the effects of the environment and culture on the health of diverse populations. The Korotkoff auscultatory technique with a trained observer and aneroid sphygmomanometer is the method of choice for blood pressure measurement in many bioanthropological field contexts. Korotkoff sounds (the first and fifth phases) are the preferred determinants of systolic and diastolic pressure, even in infants, children, pregnant women, and the elderly. Training of observers, positioning of individuals, and selection of cuff size are all essential for obtaining standardized measurements. Automatic electronic devices are increasingly being used for blood pressure measurement in human biological studies. The automatic monitors often use the oscillometric method for measuring pressure, but must be validated before use. The emergence of automatic ambulatory blood pressure monitors has opened another avenue of research on blood pressure in human biology, where allostasis and circadian responses to environmental change and real life behavioral challenges can be defined and evaluated, largely because there is now the ability to make multiple measurements over time and in varying contexts. Stand-alone automatic monitors can also be substituted for manual auscultated readings in field contexts, although in studies where participants measure their own pressure, education about how the devices work and protocol specifics are necessary. Finally, computer-driven plethysmographic devices that measure pressure in the finger are available to evaluate short-term reactivity to specific challenges.

Blood Pressure in Middle-Aged Women: A Comparison Between Office-, Self-, and Ambulatory Recordings

A blood pressure screening was carried out in women aged 40-64 years in a geographically defined area in southern Sweden; the attendance was 72%. Middle-aged women classified as normotensives by standard criteria were found to differ from hypertensives also when blood pressure was recorded with non-invasive ambulatory technique; this was so when calculated for day, night, and 24 hours. The frequency of ambulatory blood pressure values > or = 140/90 mmHg was also significantly lower in normotensives than in hypertensives. The established way of diagnosing hypertension and normotension thus correlated well with the results of ambulatory monitoring in women. Furthermore, women had their highest blood pressure in the late afternoon and not in the mornings, as previously shown in men. This was so in all three groups of women (normotensives, borderline hypertensives, and hypertensives). This difference leaves room for speculation about different types of stress load during the day in men and women.

Goal activation, expectations, and the placebo effect

Motivational factors receive little attention in current theories of the placebo effect. Reasons for this position are reviewed, and an argument is made for reconsidering the influence of motivation on the placebo effect. The authors hypothesize that nonconscious goals alter reactions to a placebo expectation. Specifically, the authors predict that the placebo effect is most likely to occur when individuals have a goal that can be fulfilled by confirmation of the placebo expectation. The authors tested this notion in 5 experiments. The results demonstrate the role of motivation in the placebo effect across a variety of symptom domains and via 4 different goal activation techniques. Moreover, this moderating effect occurred for both positive and negative placebo expectations, across different placebo effect measures, and in brief laboratory experiments as well as in lengthier studies. It is argued that theories regarding the placebo effect should incorporate motivational factors.

The joint effect of informational mood impact and performance-contingent consequences on effort-related cardiovascular response

Drawing on the mood-behavior model (G. H. E. Gendolla, 2000) and J. W. Brehm and E. A. Self's (1989) theory of effort mobilization, 2 experiments investigated the joint effect of mood, task difficulty, and performance-contingent consequences on effort-related cardiovascular response. Informational mood impact on demand appraisals and performance-contingent consequences had a joint effect on effort mobilization. When consequences were noncontingent on performance, mood interacted with task difficulty to determine cardiovascular reactivity in the shape of a cross-over interaction pattern. Yet when positive consequences were performance contingent, cardiovascular reactivity strongly increased only in the negative-mood/difficult-task condition--the subjectively appraised high necessary effort was now justified. Implications for the role of mood in motivation are discussed.

Reliability of ambulatory blood pressure monitoring

OBJECTIVE

To focus on the reliability of ambulatory blood pressure monitoring and on its limitations in clinical practice, and to construct adequate strategies to improve ambulatory monitoring performance.

METHODS

The literature was reviewed, and personal data were used.

DISCUSSION

Since the beginning of non-invasive ambulatory blood pressure monitoring, it appeared that some subjects had a high proportion of outlying readings that were unlikely to be accurate. Although ambulatory blood pressure is more reproducible than clinic blood pressure, large day-to-day differences have also been reported in reproducibility studies for average 24 h blood pressure. It has been shown that, for day-to-day 24 h blood pressure differences greater than 4/3 mmHg, ambulatory blood pressure is poorly predictive of the degree of target organ damage. The variability of average 24 h blood pressure may arise from several causes, including true biological variability, a lack of standardization of activities and measurement errors. Artefactual readings can easily occur if patients are not properly instructed. Although editing procedures can eliminate outliers, it is often impossible to identify inaccurate readings included within the patient's trend. To optimize ambulatory blood pressure monitoring, health-care providers should be instructed adequately on how to perform this technique. Appropriate patient selection, a proper application of instrumentation and the checking of its performance, careful instructions to patients, the immediate evaluation of the patient's diary and 24 h tracing after completion of the recording should improve the results of ambulatory monitoring.

CONCLUSIONS

A checklist of criteria that should be used for optimizing ambulatory monitoring in clinical practice should be proposed by the Consensus Conference on ambulatory blood pressure monitoring. To improve doctors' proficiency, strategies including educational protocols and training programmes should be implemented.

Blood pressure publication guidelines. Society for Psychophysical Research

Blood pressure is one of the most commonly recorded functions in physiology and medicine, and it has become a major variable in recent psychophysiological and behavioral medicine research. Many methods have been developed for the measurement of blood pressure in clinical, laboratory, and natural settings. The broad objectives of this report are to summarize the most critical methodological issues in the measurement of blood pressure and to present principles and recommendations for the evaluation of blood pressure methods and findings in published studies.

Evaluation of thermal biofeedback treatment of hypertension using 24-hr ambulatory blood pressure monitoring

Ten male hypertensives, whose BPs were controlled on a combination of sympatholytic and diuretic medications, were given 16 sessions of thermal biofeedback prior to attempting withdrawal from the sympatholytic drug. Results were evaluated using 24-hr ambulatory BP monitoring (ABPM) as well as clinic and home BPs, both in multi-baseline-across-subject designs and as a single group. Results showed significant treatment effects on 24-hr ABPM data, both at the individual level (SBPs only) and in the aggregate analyses (SBP and DBP). BPs assessed in the clinic by random zero sphygmomanometer and patient-assessed home BPs were also reduced.

The statistical analysis of treatment effects in 24-hour ambulatory blood pressure recordings

This paper presents a statistical analysis of treatment effects in 24-hour ambulatory blood pressure recordings. The statistical models account for circadian rhythms, subject effects, and the effects of treatment with drugs or relaxation therapy. In view of the heterogeneity of the subjects, we fit a separate linear model to the data of each subject, use robust statistical procedures to estimate the parameters of the linear models, and trim the data on a subject by subject basis. We use a meta-analytical method to combine the results of all subjects in the study.

A quantitative analysis of the effects of activity and time of day on the diurnal variations of blood pressure

The effects of activity and time of day on blood pressure (BP) were analyzed in 461 patients with untreated hypertension who wore a noninvasive portable BP recorder which took readings every 15 minutes for 24 hours. Patients recorded activity and location in a diary. The data were analyzed separately for two groups of patients: the 190 who stayed at home and the 271 who went to work. The effects of 16 different activities on BP were estimated by relating the BP to the associated activity and to the individual's clinic BP. Blood pressure was higher at work than at home, but the increment of BP for individual activities was similar in the two locations. The overall effect of activities on BP variability was computed using a one-way analysis of covariance model. For the patients who went to work this model accounted for 40% of the observed variation (R2) for systolic and 39% for diastolic BP. A similar model using time of day instead of activity accounted for 33% of variability in both systolic and diastolic BP. Combining activity and time of day was little better than activity alone (41% for both). After allowing for the effects of activity on BP, where sleep is one of the activities, there was no significant diurnal variation of BP. We conclude that there is no important circadian rhythm of BP which is independent of activity.