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Biomedical subjects

N Atkins

Publications and source records attributed to N Atkins.

17 recordsLinked to original sources
PubMed1992

The increase in blood pressure with age and body mass index is overestimated by conventional sphygmomanometry.

This cross-sectional study investigated whether the technique of blood pressure measurement used (conventional sphygmomanometry vs. ambulatory monitoring) affects the relation between blood pressure and both age and body mass index. Two independent data sets were analyzed. The first comprised 328 subjects (48% men) drawn from the population of a small Belgian town, and the second comprised 776 Irish bank employees (51% men). Age ranged from 17 years to 81 years, and body mass index (weight (kg)/height (m)2) ranged from 16.6 to 40.2. Twenty-four-hour ambulatory blood pressure was lower than blood pressure measured by a nurse in both the Belgian population sample (118/71 mmHg vs. 122/73 mmHg) and the Irish employees (118/72 mmHg vs. 119/76 mmHg). When blood pressure was measured by an observer, the well-established relations between systolic and diastolic blood pressure and both age and body mass index were evident. When the analyses were repeated using 24-hour measurements, the increment (cross-sectionally assessed) in blood pressure with age was weaker, especially in young and middle-aged subjects (20-60 years), while the increase in blood pressure with body mass index was also reduced. The within-subject differences between the conventional and ambulatory blood pressure measurements increased with older age and greater body mass index. Several other relations with blood pressure as the response variable may require revision in light of the present findings.

Adult↗
PubMed1992

Cumulative sums in quantifying circadian blood pressure patterns.

The plotting of cumulative sums (cusums), a technique of proven value in the detection of trends in data collected at intervals of time, may be modified to analyze circadian blood pressure patterns quantitatively. Mean 24-hour ambulatory blood pressure is taken as the reference value and is subtracted from each pressure value. The products of the remainders and the corresponding time intervals are summed in sequence and are plotted against time to form a modified cusum plot. The slope of the plot over any given time period equals the difference between mean blood pressure during that period and mean 24-hour blood pressure. Crest and trough blood pressures (the mean blood pressures of the 6-hour periods of highest and lowest pressures) may be identified as the 6-hour periods where plot slopes are most steeply ascending and descending, respectively. The magnitude of the circadian blood pressure change, defined as the difference between crest and trough blood pressure, is calculated from the difference between crest and trough plot slopes. The height of the cusum plot, which reflects pressure alteration extent and duration, may also be used as a measure of circadian pattern. The modified cusums technique and cusum-derived statistics are illustrated using ambulatory blood pressure profiles of hypothetical and actual hypertensive subjects. Independence from fixed time periods improves precision and reproducibility. Cusum-derived statistics are simply calculated from raw ambulatory data and should prove useful in the quantitative analysis of circadian blood pressure profiles.

Adult↗
PubMed1991

Twenty-four-hour ambulatory blood pressure in men and women aged 17 to 80 years: the Allied Irish Bank Study.

In order to determine reference values for ambulatory blood pressure, a sample of 815 healthy bank employees (399 men and 416 women), aged 17-79 years, were investigated. Ambulatory blood pressure was recorded over 24 h, taking measurements at 30-min intervals. Blood pressure was also measured by trained observers in the clinic. Ambulatory blood pressure in the 815 subjects averaged 118/72 mmHg over 24 h, 124/78 mmHg during the day (1000-2259 h) and 106/61 mmHg at night (0100-0659 h). Office blood pressure, measured by an observer, was 4/2 mmHg lower (p less than 0.0001) than daytime ambulatory pressure. The 95th centiles for the daytime ambulatory pressure in men were: 114/88 mmHg for the age group 17-29 years (n = 107); 143/91 mmHg from 30-39 years (n = 123); 150/98 mmHg from 40-49 years (n = 109); and 155/103 mmHg in 50-79 year old men (n = 60); for the corresponding age groups in women, the 95th centiles of the daytime pressure were: 131/83 mmHg (n = 174); 132/85 mmHg (n = 149); 150/94 mmHg (n = 55); and 177/97 mmHg (n = 38).

Adult↗
PubMed1991

Ambulatory blood pressure measurement in the diagnosis and management of hypertension.

Before the diagnostic potential of 24-hour non-invasive BP measurement can be assessed, the accuracy of ambulatory recorders must be established, and normal reference values determined. The accuracy criteria of four ambulatory BP measuring systems (the SpaceLabs 90207, the Novecor DIASYS 200, the Takeda TM-2420 and the Del Mar Avionics Pressurometer IV) have been assessed according to the British Hypertension Society (BHS) protocol, and the Medilog, Suntech Accutracker II and the SpaceLabs 90202 according to the standard of the Association for the Advancement of Medical Instrumentation (AAMI). The SpaceLabs 90202 and 90207, the DIASYS 200 and the Medilog fulfilled the AAMI criteria. The best devices with the BHS grading system are the SpaceLabs 90207 and the DIASYS 200. Normal reference values for daytime, night-time and 24-hour ambulatory BP have been provided by the Allied Irish Bank study of 815 healthy individuals, which showed clear age and sex differences. The mean 24-hour ambulatory pressure for the entire group was 118/72 mm Hg. 24-hour ambulatory BP measurement possesses clear advantages over conventional clinic measurement in evaluating drug efficacy, as it provides many more readings, allowing for the possibility of reducing the number of patients in antihypertensive drug studies and eliminating the need for a placebo-controlled crossover design. It allows assessment of night-time BP, which is important in view of the fact that excessive BP reduction may put patients at risk of myocardial infarction.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1991

Validation requirements for ambulatory blood pressure measuring systems.

The increasing application of ambulatory blood pressure measurement in clinical practice has stimulated the manufacture of a large number of ambulatory systems which must be independently validated. The British Hypertension Society protocol for the evaluation of blood pressure measuring devices has now been used to evaluate eight ambulatory systems. Based on this experience recommendations are made for improving validation techniques for the evaluation of ambulatory devices.

Blood Pressure Monitors↗
PubMed1991

Evaluation of the SpaceLabs 90202 non-invasive ambulatory recorder according to the AAMI Standard and BHS criteria.

The SpaceLabs 90202, a non-invasive ambulatory blood pressure recorder for the measurement of 24 hr blood pressure, was assessed according to the standard of the Association for the Advancement of Medical Instrumentation (AAMI) and the grading criteria of the British Hypertension Society (BHS) protocol were applied to the results. Two observers measured BP simultaneously in the same arm with the SpaceLabs 90202 and a standard mercury sphygmomanometer at 4 mmHg deflation steps in 85 subjects [age range 22-79 years, BP range 96-212 mmHg (systolic) and 52-134 mmHg (diastolic)]. The mean difference was -2 +/- 5 mmHg (systolic) and -2 +/- 5 mmHg (diastolic). The mean difference (+/- SD) between observers was 1 +/- 3 (systolic) and -2 +/- 3 (diastolic). The SpaceLabs 90202 fulfills the criteria of the AAMI standard (5 +/- 8 mmHg) and a B grading for both systolic and diastolic pressure is achieved with the BHS criteria.

Adult↗
PubMed1990

Inaccuracy of the Hawksley random zero sphygmomanometer.

To examine the accuracy of the Hawksley random zero sphygmomanometer two studies were done with subjects with a wide range of blood pressure. When readings made by one observer on the UK model of the Hawksley sphygmomanometer were compared with readings by two independent observers on separate mercury sphygmomanometers, the Hawksley device underestimated systolic readings by a mean (SD) of 2.0 (2.4) and 0.5 (3.6) mm Hg and diastolic readings by a mean of 3.7 (2.7) and 2.8 (2.9) mm Hg. When readings made on the UK and US models of the Hawksley sphygmomanometer were compared with those made on mercury sphygmomanometers, with observers exchanging devices half way during the experiment, the UK Hawksley device underestimated systolic pressure by a mean of 3.8 (SD 3.5) mm Hg and diastolic blood pressure by 7.5 (3.8) mm Hg; and the US model by 2.6 (3.4) mm Hg for systolic pressure and 6.2 (3.7) mm Hg for diastolic pressure. There was better agreement between two observers using standard sphygmomanometers than between an observer using the Hawksley random zero sphygmomanometer and an observer using a standard sphygmomanometer. Thus, the quantitative aspects of blood pressure in epidemiological and intervention studies in which the Hawksley random zero sphygmomanometer was used need re-evaluation. Moreover, the Hawksley random zero sphygmomanometer, in its present design, should not be used in hypertension research.

Adolescent↗
PubMed1975

Diffusing capacity, membrane diffusing capacity, capillary blood volume, pulmonary tissue volume, and cardiac output measured by a rebreathing technique.

A rebreathing method for estimating diffusing capacity, membrane diffusing capacity, pulmonary capillary blood volume, pulmonary capillary blood flow, and pulmonary tissue volume consists of rebreathing into a bag for 15 sec while acetylene, (18O)-carbon monoxide, oxygen, and helium are continuously sampled by a mass spectrometer. Because the masses of carbon monoxide and nitrogen are nearly identical at 28, it was necessary to use a stable isotope, C18O, to distinguish this gas with the mass spectrometer. Comparison of the pulmonary capillary blood flow by the rebreathing technique with the simultaneously obtained indicator dilution measurement in anesthetized dogs revealed good agreement. Estimations of pulmonary tissue volume appeared to be quite reproducible and consistent; the values tended to be somewhat smaller and less variable among normal subjects than reported by other investigators. After subtraction of capillary blood volume, tissue volume was 311 plus or minus 73 ml at rest and increased significantly to 352 plus or minus 61 ml at 75 watts of exercise. Pulmonary tissue volume in dogs using the rebreathing method averaged 9.2 ml per kg of body weight, a mean comparable to previously reported estimates using the ether plethysmographic method. The slope of pulmonary capillary blood flow (cardiac output in normal subjects) as a function of oxygen consumption during exercise in normal subjects of 0.0060 times oxygen consumption in milliliter per min was identical to published values. The rebreathing technique provides a rapid, reliable, noninvasive method for estimating pulmonary hemodynamic parameters.

Acetylene↗
PubMedDate not supplied

The quest for better validation: a critical comparison of the AAMI and BHS validation protocols for ambulatory blood pressure measurement systems.

Two validation procedures are currently available for the evaluation of ambulatory blood pressure measurement systems--the standard of the Association for the Advancement of Medical Instrumentation (AAMI) and the protocol of the British Hypertension Society (BHS). Both are in the process of revision. Four systems for measuring 24-hour ambulatory blood pressure--SpaceLabs 90207, Novacor DIASYS 200, Del Mar Avionics Pressurometer IV, and Takeda TM-2420--were evaluated according to the BHS protocol, which incorporates many of the features of the AAMI standard, under similar conditions by the same personnel and in the same subjects, so as to examine the relative merits of the two evaluation procedures. Three recorders of each model were subjected to a before-use inter-device variability test, followed by an in-use phase and an after-use inter-device variability test. The main validation test was carried out in 86 subjects with a wide range of pressures, the results being analyzed according to the BHS grading system and the AAMI validation criteria. The SpaceLabs 90207 and the DIASYS 200 achieved B and C grades, respectively, according to the BHS protocol and also satisfied the AAMI criteria for accuracy. The Pressurometer IV achieved a Grade C rating for systolic pressure and a Grade D rating for diastolic pressure and the Takeda TM-2420 achieved Grade D ratings for both systolic pressure and diastolic pressure. Both these devices failed to fulfil the AAMI criteria for accuracy and both failed to function in the main validation test and had to be replaced.(ABSTRACT TRUNCATED AT 250 WORDS)

Ambulatory Care↗