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Biomedical subjects

E O'Brien

Publications and source records attributed to E O'Brien.

At least 163 records · Page 9Linked to original sources
PubMed1993

Relationship between blood pressure measured in the clinic and by ambulatory monitoring and left ventricular size as measured by electrocardiogram in elderly patients with isolated systolic hypertension.

OBJECTIVE: To assess the additional diagnostic precision conferred by ambulatory blood pressure monitoring on clinic blood pressure measurement in evaluating the severity of isolated systolic hypertension. METHODS: The association between left ventricular size as determined by ECG voltages [R-wave voltages in lead V5 (RV5) and S-wave voltages in lead V1 (SV1)] and blood pressure as assessed by clinic measurements and ambulatory blood pressure monitoring was studied in 97 elderly patients included in the placebo run-in phase of the Syst-Eur trial. The additional diagnostic precision conferred by ambulatory monitoring on clinic blood pressure measurements was assessed by relating the residual ambulatory blood pressure level to the ECG-left ventricular size. The residual ambulatory blood pressure level was calculated by subtracting the predicted ambulatory blood pressure level for each patient (using the linear regression equation relating both techniques for the group) from the observed ambulatory blood pressure. RESULTS: Clinic systolic blood pressure was on average 20 mmHg higher (P < 0.001) than daytime ambulatory blood pressure while diastolic blood pressure was similar with both techniques. The sum of SV1 + RV5 was significantly related to clinic systolic pressure (r = 0.25), and 24-h (systolic, r = 0.37; diastolic, r = 0.29), daytime (systolic, r = 0.30; diastolic, r = 0.19) and night-time (systolic, r = 0.33; diastolic, r = 0.28) ambulatory blood pressure levels. These findings were not affected by adjustment for gender, age and the body mass index. The sum of SV1 + RV5 was significantly related to the residual 24-h (systolic, r = 0.30; diastolic, r = 0.31), daytime systolic (r = 0.20) and night-time (systolic, r = 0.31; diastolic, r = 0.29) ambulatory blood pressure monitoring levels. CONCLUSION: Ambulatory blood pressure monitoring adds to the diagnostic precision of clinic blood pressure measurement in assessing the severity of hypertension in this population. The ongoing side project on ambulatory blood pressure monitoring in the Syst-Eur study should establish whether these findings hold true for morbidity and mortality.

Aged↗
PubMed1993

Comparative accuracy of six ambulatory devices according to blood pressure levels.

OBJECTIVE: To assess the accuracy of six ambulatory blood pressure measuring systems at low, medium and high blood pressures. RESULTS: The CH-Druck, Profilomat, SpaceLabs 90207 and Novacor DIASYS 200R, having previously achieved A to C grading for systolic and diastolic blood pressures according to the British Hypertension Society (BHS) protocol and having fulfilled the criteria of the Association for the Advancement of Medical Instrumentation, have been recommended for measurement of ambulatory blood pressure in clinical practice; the Pressurometer IV and Takeda TM-2420, achieved only C and D grades and failed to satisfy the Association for the Advancement of Medical Instrumentation criteria. In this study the data from the original validations are re-analysed for three pressure ranges of systolic and diastolic blood pressures: low range < or = 130/80 mmHg, medium range 130-160/80-100 mmHg and high range > or = 160/100 mmHg. All six devices maintained their overall grading or improved them slightly in the low and medium blood pressure ranges, but in the high blood pressure range the CH-Druck slipped from an overall A/A grading to B/C, the Profilomat from B/A to C/D, the SpaceLabs from B/B to C/C and the Pressurometer IV from C/D to D/D. The Takeda remained unchanged with a D grading, but the results within this grading were worse in the higher blood pressure range, and the Novacor rose from C/C to C/B. CONCLUSIONS: This analysis suggests that the CH-Druck is the most accurate ambulatory system across the pressure range, although it does not perform as well in the high blood pressure range as in the medium and low blood pressure ranges. The SpaceLabs 90207 is accurate in the low and medium blood pressure ranges and reasonably accurate in the high blood pressure range. If blood pressures only in the low and medium ranges are to be measured, a wider selection of ambulatory systems becomes available because, in addition to the CH-Druck and SpaceLabs 90207, the Profiloat and Novacor DIASYS 200R are accurate.

Blood Pressure↗
PubMed1993

Twenty-four-hour ambulatory blood pressure measurement in a primigravid population.

OBJECTIVE: To establish the profiles of 24-h non-invasive ambulatory blood pressure measurement (ABPM) during the trimesters of pregnancy and the puerperium in normotensive healthy primigravidae. DESIGN: A prospective study in which 24-h ABPM was performed on five occasions in each subject: in the first trimester between 9 and 16 weeks' gestation; in the second trimester between 18 and 24 weeks; in the third trimester between 26 and 32 weeks and between 33 and 40 weeks; and finally at 6 weeks post partum. METHOD: One hundred and six Caucasian primigravid women who were normotensive at their first booking visit were recruited consecutively from the antenatal clinic and had 24-h ABPM performed with the SpaceLabs 90207 ambulatory system. RESULTS: Of the 106 women recruited, 98 completed 24-h ABPM on four of the five measurement occasions. Four women delivered prematurely before 33 weeks' gestation, thereby missing one ABPM measurement. Changes during pregnancy and the puerperium were assessed against the ABPM performed in the first trimester. There was no difference for daytime or night-time systolic blood pressure between 9 and 33 weeks, but it rose significantly from 33 to 40 weeks. At 6 weeks post partum, systolic blood pressure was not significantly different from the daytime pressure in the first-trimester ABPM but was raised significantly at night. Diastolic blood pressure decreased significantly between 18 and 24 weeks for both daytime and night-time. From 33 to 40 weeks it increased in parallel with systolic blood pressure, and at 6 weeks post partum it was raised significantly compared with first-trimester values for daytime and night-time. The nocturnal fall in blood pressure was preserved throughout pregnancy with a significant difference between daytime and night-time measurements present on all measurement occasions for systolic, diastolic and mean blood pressures and heart rate. There were significant differences between daytime ABPM and clinic blood pressure for both systolic and diastolic blood pressure up to 33 weeks. From 33 weeks until 6 weeks post partum there was no significant difference between daytime ambulatory and clinic blood pressures. CONCLUSION: This study provides reference values for ABPM in healthy primigravidae with generally uncomplicated pregnancies.

Adult↗
PubMed1993

Antihypertensive therapy and circadian blood pressure profiles: a retrospective analysis utilising cumulative sums.

The results of previous studies on the effects of antihypertensive agents on circadian blood pressure patterns are inconclusive, possibly due to the lack of a simple, objective, universally accepted method of quantifying circadian blood pressure profiles. In order to investigate for differences in the effects of antihypertensive drugs on circadian changes we utilised a recently described modified cumulative sums technique to quantify circadian alteration magnitude (CAM). CAM is simply calculated as the difference between crest and trough blood pressures, the mean blood pressures of the 6-h periods of highest and lowest sustained pressures respectively. The records from all 24-h ambulatory blood pressure monitoring performed over a 7 year period on subjects either on no medication (1208), or on treatment with a single first-line antihypertensive agent (578), were examined retrospectively. A sample (n = 40) stratified for trough diastolic blood pressure, age and sex was randomly selected from each of the following 5 groups: subjects on no medication, and subjects being treated with bendrofluazide, atenolol, class 2 calcium-channel blockers or captopril alone. Untreated subjects, those on bendrofluazide and those on a class 2 calcium channel blocker had similar circadian patterns. Subjects on atenolol therapy (25.9 +/- 1.7/18.3 +/- 1.3, systolic CAM +/- SE/diastolic CAM +/- SE) had attenuated circadian changes (p < 0.05) when compared to the untreated group (29.8 +/- 1.8/23.6 +/- 1.1), while those on captopril (34.9 +/- 2.4/25.7 +/- 1.8) exhibited markedly increased systolic and diastolic circadian blood pressure swings, which differed from those of the atenolol treated group (p < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

Evaluation of blood pressure measuring devices.

Validation of blood pressure measuring devices is a relatively new field of research. There are two national protocols for validating blood pressure measuring devices: the protocol of the American Association for the Advancement of Medical Instrumentation (AAMI) and the protocol of the British Hypertension Society (BHS), each of which has recently been revised. 19 blood pressure measuring devices have been validated according to one or both of these protocols. These protocols have been beneficial in drawing attention to the potential inaccuracy of blood pressure measuring systems, they permit comparison between devices and they have brought manufacturers of blood pressure measuring devices into closer contact with the profession. There are some inherent weaknesses in both protocols which include the fallibility of the 'gold standard', the lack of provision for validation in special circumstances and in special groups, such as the elderly and pregnant women, and failure to allow for deteriorating accuracy with higher pressure levels. The revised BHS protocol attempts to redress these deficiencies.

Blood Pressure Monitors↗
PubMed1993

Nitrendipine in older patients with isolated systolic hypertension: second progress report on the SYST-EUR trial.

This report from the double-blind placebo-controlled SYST-EUR trial investigated whether modern antihypertensive drugs are suitable for maintaining long-term BP control in older (> or = 60 years of age) subjects with isolated systolic hypertension (SBP 160-219 mmHg and DBP < 95 mmHg). Active treatment consisted of nitredipine (10-40 mg/day) with the possible addition of enalapril (5-20 mg/day) and hydrochlorothiazide (12.5-25 mg/day), if necessary to reduce SBP to < 150 mmHg and by > or = 20 mmHg. Matching placebos were used in the control group. This analysis was restricted to 18 months of follow-up. The placebo (n = 456) and active treatment (n = 485) groups had similar characteristics at randomisation (sitting pressure 176/85 mmHg; age 73 years). SBP fell (P < 0.001) on average 10 mmHg more on active treatment than on placebo and DBP 4 mmHg more. Fewer patients remained on monotherapy in the placebo than in the active treatment group (P < 0.001); on placebo the second and third line medications were started earlier (P < 0.001). Nitrendipine tablets were discontinued in nine patients on placebo and in 29 patients assigned to active treatment (P < 0.001). In conclusion, a significant BP reduction can be achieved and maintained in older patients with isolated systolic hypertension treated with a calcium antagonist (associated with a converting-enzyme inhibitor and a thiazide, where necessary). Whether this BP reduction results in a clinically meaningful decrease of cardiovascular complications is under investigation.

Aged↗
PubMed1993

Defining normal ambulatory blood pressure.

Providing normal reference values and the means to interpret such values in practice is an urgent issue requiring consensus. Five basic approaches to defining normalcy for 24 h blood pressures (BP) are considered: 1) the relationship of ambulatory blood pressure (ABP) to morbidity and mortality, 2) the relationship of ABP to end-organ involvement, 3) ABP levels in normal populations, 4) the relationship of ABP to clinic BP, and 5) the relationship of 24 h indices to risk. Although there now is considerable evidence demonstrating that ambulatory measurement correlates more strongly with end-organ damage, the first two approaches are scientifically the best. It will be some time before levels of normalcy can be derived. There is a large volume of data on population samples permitting derivation of normalcy for clinical practice. Rounded upper limits of normal can be calculated as 140/90 mm Hg for 24 h ambulatory pressure, 150/90 mm Hg for daytime pressure, and 130/80 mm Hg for nighttime pressure. There are, however, considerable differences for age and gender which need to be taken into consideration.

Ambulatory Care↗
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

Effects of aging and hypertension on plasma angiotensin II and platelet angiotensin II receptor density.

Plasma renin activity (PRA) declines with age in normal individuals, but the effect of age on plasma angiotensin II (ANG II) is less clear. A decline in plasma ANG II with age could result in altered platelet ANG II receptor density since plasma hormone levels influence their target organ receptors. To investigate this possibility, PRA, plasma ANG II, and platelet ANG II receptor density were examined in 17 young, 12 middle-aged, and 14 elderly healthy normotensive volunteers. To assess whether hypertension altered receptor density, these variables were also examined in 23 hypertensive patients. In normotensives, there was a negative correlation between age and PRA (r = -0.43, P < .05), no significant change in basal plasma ANG II with age, and a weak positive correlation between age and ANG II receptor density (r = 0.34, P < .05). Multiple regression analysis revealed that the relationship between age and ANG II receptor density was independent of the associated rise in mean arterial pressure with age (P < .05). Platelet ANG II receptor density was not significantly related to PRA or plasma ANG II. ANG II receptor affinity did not change with age. Neither PRA nor ANG II receptor density or affinity differed between hypertensives and normotensives of similar mean age, but plasma ANG II was significantly lower in hypertensives compared with normotensives. We concluded that aging is associated with a decline in supine PRA. The small decrease in plasma ANG II was not significant. Platelet ANG II receptor density increased with age primarily due to a small group of elderly subjects with elevated receptor density. There was no change in ANG II receptor density or affinity in hypertensives despite apparently lower plasma ANG II in these patients.

Adult↗
PubMed1992

The diurnal blood pressure profile. A population study.

This population study included 399 subjects, of whom 370 (93%) showed a significant diurnal blood pressure (BP) rhythm. The nocturnal BP fall was normally distributed and averaged 16 +/- 9 mm Hg systolic and 14 +/- 7 mm Hg diastolic (mean +/- SD). The amplitude of the diurnal BP curve followed a positively skewed distribution, with a mean of 16 +/- 5 mm Hg for systolic BP and 14 +/- 4 mm Hg for diastolic BP. The daily BP maximum occurred at 15:54 +/- 4:47 for systolic BP and at 15:11 +/- 4:20 for diastolic BP. Thirty-four subjects were reexamined after a median interval of 350 days. The test for the presence of a significant diurnal rhythm was discordant in only two subjects. Repeatability (twice the standard deviation of the differences between paired recordings expressed as a percentage of the mean) varied from 11 to 25% for the 24 h, daytime, and overnight BP, and from 76 to 138% for the parameters describing the diurnal BP rhythm. In nine subjects with an initial night/day ratio of mean BP less than 0.78, the nighttime BP was significantly increased at the repeat examination, whereas the opposite tendency was observed in nine subjects with an initial ratio greater than 0.87. In conclusion, the distribution of the nocturnal BP fall is unimodal. The reproducibility of the ambulatory BP is satisfactory for the level of BP and for the presence of a diurnal BP rhythm, but not for the parameters of the diurnal BP curve. Thus, one 24 h recording is insufficient to fully characterize an individual's diurnal BP profile.

Adult↗