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Biomedical subjects

N Atkins

Publications and source records attributed to N Atkins.

At least 19 recordsLinked to original sources
PubMed2004

Determinants of white-coat hypertension.

BACKGROUND: The prevalence of white-coat hypertension (WCH) is considerable in patients referred with elevated office blood pressure. Failure to recognise this phenomenon can lead to the inappropriate use of antihypertensive medications. We undertook this study to determine the profile of patients with WCH. METHODS: Baseline clinic and daytime ambulatory blood pressures were available from 5716 patients referred over a 22-year period. Individuals were considered to have WCH if they had an elevated clinic blood pressure measurement greater than 140/90 mmHg and normal daytime mean ambulatory blood pressure. Mean age was 53.6 years and 53.2% were female. RESULTS: The overall prevalence of white-coat hypertension was 15.4%. A higher prevalence was seen amongst older adults, females, and non-smokers. CONCLUSION: Multivariate logistic regression analysis confirmed these characteristics as independent predictors of WCH.

Blood Pressure Determination↗
PubMed2000

Emx1-specific expression of foreign genes using "knock-in" approach.

Emx1 is a mouse homologue of the Drosophila homeobox gene empty spiracles. Its expression is limited to the neurons in developing and adult cerebral cortex and hippocampus. Because of the highly restricted expression pattern of the Emx1 gene, it would be quite desirable to characterize the promoter of the Emx1 for directing foreign gene expression in the transgenic mouse. We report here that we have achieved the Emx1-specific expression in transgenic mice by inserting the lacZ reporter and cre genes directly into the exon 1 of the Emx1 gene using embryonic stem (ES) cell technology. The distribution of the beta-galactosidase activity in the transgenic mice was consistent with the published results obtained using in situ hybridization and immunohistochemistry. Furthermore, we have demonstrated that Cre protein was present in the cerebral cortex of the transgenic mice and was able to mediate loxP-specific recombination in vitro. The creation of this line of cre transgenic mice, and the demonstration that the insertion site located in the exon 1 of the Emx1 gene could render foreign genes a specific expression pattern restricted to the developing and adult cerebral cortex and hippocampus, should be conducive to further studies of the effect of a gene mutation or overexpression upon the development and plasticity of cerebral cortex and hippocampus.

Animals↗
PubMed1999

Evaluation of the Schiller BR-102 ambulatory blood pressure system according to the protocols of the British Hypertension Society and the Association for the Advancement of Medical Instrumentation.

OBJECTIVE: To evaluate the Schiller BR-102 monitor for ambulatory blood pressure measurement according to the protocols of the British Hypertension Society (BHS) and the Association for the Advancement of Medical Instrumentation (AAMI). DESIGN: The BHS protocol is divided into two parts. Part I, which is the part applicable to this study, comprises the main validation procedure and has five phases: before-use device calibration; in-use (field) phase; after-use device calibration; static device validation; and report of evaluation. METHOD: Three Schiller BR-102 recorders passed the before-use device calibration test, after which they entered the in-use (field) assessment phase during which the three recorders were each worn by 10 subjects for 24 h, after which calibration was again assessed. Because there was no difference in results of calibration testing among the three devices, one was selected randomly and the main validation test was carried out on 85 subjects with a wide range of blood pressures both for the auscultatory mode and for the oscillometric mode using the Sphygmocorder. The results were analysed according to the BHS grading system from A to D. The data were also analysed according to the standard of the Association for the Advancement of Medical Instrumentation (AAMI), which stipulates that the mean difference between the test device and the standard shall be </= 5 mmHg with a standard deviation of </= 8 mmHg. RESULTS: The Schiller BR-102 achieved a BHS grade B rating for systolic and diastolic blood pressures in the auscultatory mode and satisfied the criteria for accuracy of the AAMI protocol for systolic and diastolic blood pressures. In the oscillometric mode, the Schiller BR-102 achieved grade D for systolic blood pressure and grade B for diastolic blood pressure according to the BHS protocol and satisfied the AAMI criteria for diastolic but not systolic blood pressure. Applying the BHS and AAMI criteria to tertiles of blood pressure (low-pressure range < 130/80 mmHg, medium-pressure range 130-160/80-100 mmHg, high-pressure range > 160/100 mmHg) the Schiller BR-102 was less accurate in the high pressure range for diastolic blood pressure but more accurate for systolic blood pressure, achieving A/C grading, while satisfying the AAMI criteria both for systolic and for diastolic blood pressure in the auscultatory mode. In the oscillometric mode the device performed less accurately in the high-pressure range, achieving grade D/C, while failing to satisfy the AAMI criteria both for systolic and for diastolic blood pressure. The means+/-SD of the first mercury sphygmomanometer measurements were 143+/-32 mmHg for systolic blood pressure and 88+/-21 mmHg for diastolic blood pressure. Acceptability to subjects was good and the manufacturer's manual was satisfactory. CONCLUSION: On the basis of these results, the Schiller BR-102 can be recommended for ambulatory blood pressure measurement in clinical practice using the auscultatory mode, but the oscillometric mode, which operates only if the device fails in the auscultatory mode, does not provide accurate measurements.

Blood Pressure↗
PubMed1999

Diagnosis of white coat hypertension by ambulatory blood pressure monitoring.

White coat hypertension (WCH) is common in referred hypertensive patients. Ambulatory blood pressure monitoring (ABPM) is not free from the white coat syndrome. We examined the use of the elevation of the first and last measurements of ABPM for diagnosis of WCH in a hypertensive population that had been referred to a hospital-based hypertension unit. Data were obtained on 1350 patients for clinic and ABPM parameters. WCH, as diagnosed by conventional clinic blood pressure (BP) measurement, was compared with a variety of alternative methods determined from ABPM. In all cases, mean daytime pressure was <135 mm Hg/85 mm Hg with an elevation of clinic BP >/=140 mm Hg systolic or 90 mm Hg diastolic. The definitions tested for this elevation were first hour mean pressure, first reading, maximum reading in first hour, last hour mean pressure, last reading, maximum reading in the last hour and maximum reading in first or last hour. Elevation of the maximum pressure in the first hour or last hour above 140 mm Hg systolic or 90 mm Hg diastolic showed a high level of agreement (kappa=0.91) with classical WCH for diagnosis of the white coat syndrome. Termed ambulatory white coat hypertension, patients with this finding were older than classic white coat patients and had higher daytime (127+/-6/78+/-5 mm Hg versus 121+/-5.5/74+/-6 mm Hg, P<0.005 for systolic and diastolic) and nighttime (114+/-11/67+/-8 mm Hg versus 106+/-9/61+/-6 mm Hg, P<0.005 for systolic and diastolic) pressures. They also had a significantly greater Sokolow-Lyon index (leads V(1)+V(5), 21+/-7 mV versus 18+/-6 mV). Elevation of BP above 140 mm Hg systolic or 90 mm Hg diastolic in the first or last hour of monitoring diagnoses patients with a white coat response in whom there is a higher BP profile than in patients with classic white coat response alone. We suggest, therefore, that this is a better measure of the white coat phenomenon.

Adult↗
PubMed1998

Sensitization to human leukocyte antigen before and after the introduction of erythropoietin.

INTRODUCTION: Antibodies directed against human leukocyte antigens (HLAs) impact adversely on renal transplantation. Measures aimed at preventing such antibody formation are thus important. The introduction of recombinant human erythropoietin (rHuEpo) has permitted the reduction of blood transfusion in patients with chronic renal failure. The impact of rHuEpo on the incidence of sensitization in patients awaiting transplantation was therefore studied. METHODS: A retrospective analysis of the patients awaiting transplantation before (group A) and 4 years after (group B) the introduction of rHuEpo was performed in order to ascertain changing patterns in the use of blood transfusion and causes of sensitization. RESULTS: The total number of transfusions administered to haemodialysis patients decreased by 34% during the study period. This was accompanied by a significant reduction in the ratio of blood transfusion to haemodialysis treatment episodes (0.095 in group A to 0.06 in group B, P = 0.001). The number of patients sensitized as a consequence of blood transfusion decreased from 63% in group A to 28% in group B (P = 0.0004). The overall incidence of sensitization decreased from 50% in group A to 36.5% in group B (P = 0.008). This decrement was associated with a significant reduction in the mean waiting time for transplantation (42.1 +/- 1.1 vs 15.4 +/- 2.4 months, P < 0.0001). The incidence of sensitization due to previous transplantation increased during the study period from 41% in group A to 77% in group B, (P = 0.0004). There was no change in the number of patients sensitized due to pregnancy. CONCLUSION: The introduction of rHuEpo has resulted in a significant decrease in the requirements for blood transfusion among patients awaiting transplantation and is associated with a significant reduction in transfusion-related sensitization and mean waiting time for transplantation.

Blood Transfusion↗
PubMed1998

Evaluation of the Profilomat II ambulatory blood pressure system according to the protocols of the British Hypertension Society and the Association for the Advancement of Medical Instrumentation.

OBJECTIVE: To evaluate the Profilomat II monitor for ambulatory blood pressure measurement according to the protocols of the British Hypertension Society (BHS) and the Association for the Advancement of Medical Instrumentation (AAMI). DESIGN: The BHS protocol is divided into two parts. Part I, which is the part applicable to this study, comprises the main validation procedure and has five phases: before-use device calibration; static device validation; and report of evaluation. METHOD: Three Profilomat II recorders passed the before-use device calibration test. They then entered the in-use (field) assessment phase during which the three recorders were each worn by ten subjects for 24-h, after which the calibration was again assessed. Since no difference in calibration testing was observed between the three devices, one was selected randomly and the main validation test was carried out in 85 subjects, who had a wide range of blood pressures, using the sphygmocorder. The results were analysed according to the BHS grading system from A to D. The data was also analysed according to the standard of the Association for the Advancement of Medical Instrumentation (AAMI) which stipulates that the mean difference between the test device and the standard shall be </= 5 mmHg with a standard deviation of </= 8 mmHg. RESULTS: The Profilomat II achieved a BHS grade C rating for systolic blood pressure and grade B for diastolic blood pressure; it satisfied the criteria for accuracy of the AAMI for diastolic but not systolic blood pressure. When the BHS and AAMI criteria were applied to tertiles of pressure (low pressure range < 130/80 mmHg, medium pressure range 130-160/80-100 mmHg, high pressure range > 160/100 mmHg), the Profilomat II was less accurate in the high pressure range, achieving a D/C grading, and failed the AAMI criteria for systolic and diastolic blood pressures. The mean and standard deviation of the first mercury sphygmomanometer measurements were 145+/-34/87+/- 20 mmHg. Subject acceptability was good and the manufacturers manual was satisfactory. CONCLUSION: On the basis of these results, the Profilomat II cannot be recommended for ambulatory blood pressure measurement in clinical practice where accurate measurements are required.

Adolescent↗
PubMed1997

Accuracy of the Dinamap Portable Monitor, model 8100: a review of the evidence for accuracy.

Conventional measurement of blood pressure is fraught with many potential errors '1'. Automated blood pressure measuring devices remove observer bias and permit repeated blood pressure measurements at predetermined intervals, features which have obvious attractions in clinical practice and in hypertension and epidemiological research. However, such devices, which can be expensive, must be shown to be as accurate as the conventional technique which they are designed to replace '2'. A number of Dinamap models are available '3', the Dinamap Portable Monitor, Model 8100 (Critikon, Tampa, Flirida, USA) being one of the most popular automated devices used in clinical practice and in hypertension research, despite reports demonstrating that it is inaccurate in certain clinical circumstances. We therefore decided to review the literature on the Dinamap 8100. Ten papers '4-13' concerned specifically with the accuracy of this model were identified; they all acknowledged its inaccuracy but not all reached the same conclusions regarding the influence of such inaccuracy in practice.

Journal Article↗
PubMed1997

Increasing observer objectivity with audio-visual technology: the Sphygmocorder.

The most fallible component of blood pressure measurement is the human observer. The traditional technique of measuring blood pressure does not allow the result of the measurement to be checked by independent observers, thereby leaving the method open to bias. In the Sphygmocorder, several components used to measure blood pressure have been combined innovatively with audio-visual recording technology to produce a system consisting of a mercury sphygmomanometer, an occluding cuff, an automatic inflation-deflation source, a stethoscope, a microphone capable of detecting Korotkoff sounds, a camcorder and a display screen. The accuracy of the Sphygmocorder against the trained human observer has been confirmed previously using the protocol of the British Hypertension Society and in this article the updated system incorporating a number of innovations is described.

Journal Article↗
PubMed1996

Evaluation of three devices for self-measurement of blood pressure according to the revised British Hypertension Society Protocol: the Omron HEM-705CP, Philips HP5332, and Nissei DS-175.

OBJECTIVE: We evaluated three devices for self-measurement of blood pressure - the Omron HEM-705CP, the Philips HP5332 and the Nissei DS-175 - according to the revised protocol of the British Hypertension Society (BHS). The results were also analysed according to the criteria for accuracy of the revised standard of the Association for the Advancement of Medical Instrumentation (AAMI). DESIGN: The revised BHS protocol is divided into two parts. Part I, the part applicable to this study, comprises the main validation procedure and has five phases: Before-use device calibration; in-use (field) phase; after-use device calibration; static device validation; report of evaluation. METHODS: Three models of each device passed the before-use device calibration test, after which they entered the in-use phase, which involved use of the three recorders for a month; inter-device calibration was assessed again at the end of the month. There was no difference in calibration testing between the three models of each device, and therefore one of each was selected randomly; the main validation test was carried out in 85 subjects with a wide range of pressures, and the results were analysed according to the BHS grading system from A to D. RESULTS: The Omron HEM-705CP achieved an overall B/A grading and fulfilled the AAMI accuracy criteria; the Philips HP5332 achieved an overall C/A grading and failed the AAMI accuracy criteria for measuring systolic pressure; the Nissei DS-175 achieved an overall D/A grading and failed the AAMI accuracy criteria for measuring systolic pressure. When the BHS and AAMI criteria were applied to tertiles of pressure (low-pressure range < 130/80 mmHg; medium-pressure range 130-160/80-100 mmHg; high-pressure range > 160/100 mmHg) all three devices were less accurate in the high-pressure range: the Omron HEM-705CP achieved C/B grading while continuing to fulfil the AAMI criteria; the Philips HP5332 dropped to D grading for systolic pressure and the Nissei DS-175 achieved a lower D grading for systolic pressure. The mean and standard deviation of the first mercury sphygmomanometer measurements were 148+/-35/88+/-22 mmHg. Acceptability by the users was good and the manufacturer's manual was satisfactory for all three devices. CONCLUSIONS: On the basis of these results, the Omron HEM-705CP was the most accurate of the three devices tested, achieving Grade B for systolic and Grade A for diastolic pressure, as well as fulfilling the AAMI criteria for accuracy for both systolic and diastolic pressure. It can therefore be recommended for the clinical measurement of blood pressure and is the first inexpensive device to satisfy the accuracy criteria of these protocols.

Journal Article↗
PubMed1995

The ambulatory blood pressure in normotensive and hypertensive subjects: results from an international database.

OBJECTIVE: To delineate more precisely an operational threshold for making clinical decisions based on ambulatory blood pressure (ABP) measurement by studying the ABP in subjects who were diagnosed as either normotensive or hypertensive by conventional blood pressure (CBP) measurement. SUBJECTS: Twenty-four research groups recruited 7069 subjects. Of these, 4577 were normotensive (systolic CBP < or = 140 mmHg and diastolic CBP < or = 90 mmHg) and 1773 were hypertensive (systolic CBP > or = 160 mmHg and/or diastolic CBP > or = 90 mmHg). Of the latter, 1324 had systolic and 1310 had diastolic hypertension. RESULTS: Ninety-five percent of the normotensive subjects had a 24-h ABP below (systolic and diastolic, respectively) 133 and 82 mmHg. Of the patients with systolic hypertension, 24% had a 24-h systolic ABP of < 133 mmHg. Similarly, 30% of those with diastolic hypertension had a 24-h diastolic ABP of < 82 mmHg. The probability that hypertensive patients had a 24-h ABP below these thresholds was higher in women than in men, increased with age and was 2- to 4-fold greater if the CBP of the patient had been measured at only one visit and if fewer than 3 CBP measurements had been averaged to establish the diagnosis of hypertension. By contrast, for each 10-mmHg increment in systolic CBP, this probability decreased by 54% for the 24-h systolic ABP and by 25% for the 24-h diastolic ABP, and for each 5 mmHg increment in diastolic CBP it increased by 6 and 9%, respectively. CONCLUSION: The ABP distributions of the normotensive subjects included in the present international database were not materially different from those in previous reports in the literature. One-fifth to more than one-third of the hypertensive patients had an ABP which was below the 95th centile of the ABP in normotensive subjects, but this proportion decreased if the hypertensive patients had shown a higher CBP upon repeated measurement. The prognostic implications of elevated CBP in the presence of normal ABP remain to be determined.

Adolescent↗
PubMed1995

State of the market. A review of ambulatory blood pressure monitoring devices.

The introduction of 24-hour ambulatory blood pressure measurement into clinical practice created a large market for ambulatory blood pressure measurement devices. Forty-three such devices from 31 manufacturers or suppliers are now available to satisfy a market demand that is likely to increase. The aim of this article is to identify the devices available and then to examine critically any validation studies assessing accuracy and performance. Of the 43 devices available 18 have been validated according to the protocols of the Association for the Advancement of Medical Instrumentation (AAMI) or the British Hypertension Society (BHS) in 25 reported studies. In 9 of these studies the protocol was not adhered to, and the results, which are therefore questionable, are noted but not considered further. Fourteen devices were evaluated according to the accuracy criteria of both protocols, and of these 9 fulfilled the requirements. From this review of 43 devices on the market it may be concluded that, at the time of writing, there is published evidence for only 9 devices meeting the generally accepted AAMI and BHS criteria for accuracy and performance; these are the A&D TM-2420 models 6 and 7 and TM-2421, CH-Druck, Nissei ABPM DS-240, Profilomat, QuietTrak, and SpaceLabs SL-90202 and SL-90207.

Blood Pressure Monitoring, Ambulatory↗