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Biomedical subjects

E O'Brien

Publications and source records attributed to E O'Brien.

At least 91 records · Page 5Linked to original sources
PubMed1998

Automated blood pressure measurement: state of the market in 1998 and the need for an international validation protocol for blood pressure measuring devices.

The market for blood pressure measuring devices is increasing rapidly. A vast market for self-measuring devices has existed for many years and this continues to grow. There is also a large market for autoated devices in specialized hospital areas, such as operating theatres and intensive care units. Since the introduction of ambulatory blood pressure monitoring into clinical practice, a growing market for devices to measure blood pressure over time has been created. The states of these three markets are reviewed in this paper. With the likely banning of mercury from clinical use, the traditional sphygmomanometer will disappear and it is inevitable that a new and large market will be created by the demand for an automated alternative to the mercury sphygmomanometer in hospitals and in general practice. It is mandatory that such automated devices are validated independently for accuracy and performance. At present two validation protocols are widely used to test the accuracy of blood pressure measuring devices - the British Hypertension Society and the Association for the Advancement of Medical Instrumentation protocols. These protocols have a common purpose and many similarities. It is proposed that a common protocol should be devised for international use. Experience with these protocols allows one to make suggestions concerning how such an international protocol might be simplified and improved.

Journal Article↗
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↗
PubMed1998

Arthroscopic microdiscectomy and selective fragmentectomy.

A prospective outcome study to determine the efficacy and complications associated with posterolateral arthroscopic discectomy was initiated in April 1988. One hundred seventy-five patients with symptoms consistent with a lumbar disc herniation and correlative imaging studies were treated operatively, and 169 were available for followup evaluation. Fifty-nine patients with a central herniation or a nonmigrated sequestered fragment were treated using bilateral biportal posterolateral access, whereas 116 patients with radiographic evidence of a paramedial, foraminal, or extra-foraminal herniation were treated using the unilateral uniportal approach. The minimum duration of nonoperative management ranged from 3.5 to 28 months (average, 16 months), and all patients had a minimum of 24 months of postoperative followup. Outcome analysis indicated that 149 procedures were successful, whereas 20 (11.8%) procedures were failures because of persistent radicular symptoms that, in some cases, required open laminotomy. Complications associated with the procedures included one disc space infection, one transient peroneal neuropraxia, and four index extremity skin hypersensitivity. All of these complications resolved without sequelae, and there were no neurovascular complications directly related to the surgical approach.

Arthroscopy↗
PubMed1998

Coronary stenting in unstable angina: early and late clinical outcomes.

OBJECTIVE: To examine the procedural and long term success of coronary stenting in patients presenting with unstable angina and the effect of warfarin on the clinical outcome of these high risk patients. DESIGN: A nonrandomized, retrospective analysis of patients presenting with unstable angina. SETTING: A tertiary care, Canadian university-affiliated teaching hospital. PATIENTS: Of 1250 patients who underwent percutaneous transluminal coronary angioplasty between January 1994 and June 1995, 365 underwent coronary stenting. The study population consisted of the 156 patients presenting with unstable angina who underwent coronary stenting. Patients with Canadian Cardiovascular Society class IV and postinfarction angina were included. INTERVENTIONS: Stent delivery by standard techniques to the target lesion was successful in all patients. At discharge, 88 patients were prescribed warfarin, ticlopidine and acetylsalicylic acid (ASA); the remaining 68 patients received only ticlopidine and ASA. Late clinical outcomes were assessed by telephone interview. RESULTS: The overall procedural success rate was 96%. One patient died in hospital (0.6%). Other events were abrupt closure (1.9%), myocardial infarction (1.9%) and urgent bypass surgery (1.9%). During follow-up, target vessel reintervention was needed in 19.6% of patients. Early and late clinical outcomes did not differ significantly between anticoagulated patients and those treated with antiplatelet agents alone, but anticoagulated patients had a significantly longer hospital stay. CONCLUSIONS: Coronary stenting in patients with unstable angina was associated with excellent procedural success and favourable late clinical outcomes. Warfarin added no apparent additional clinical benefit to antiplatelet agents in this high risk population.

Angina, Unstable↗
PubMed1997

Can 24-hour ambulatory blood pressure measurement predict the development of hypertension in primigravidae?

OBJECTIVE: To assess the role of 24-hour ambulatory blood pressure measurement in the mid-second trimester as a predictive test for the development of hypertension in pregnancy. DESIGN: Prospective intervention. SETTING: The Rotunda Hospital, Dublin. PARTICIPANTS: One thousand one hundred and two healthy primigravid women. INTERVENTION: 24-hour ambulatory blood pressure measurement at 18 to 24 weeks of gestation. MAIN OUTCOME MEASURES: The development of pre-eclampsia or gestational hypertension. RESULTS: A total of 1048 women had sufficient readings to be included in the final analysis. Of these, 23 (2.2%) developed pre-eclampsia, 64 (6.1%) developed gestational hypertension and 961 (91.7%) remained normotensive. Significantly higher ambulatory blood pressures were recorded in both the pre-eclamptic and gestational hypertensive group compared with the normotensive group. In addition, the gestational hypertensive group had significantly higher clinically measured blood pressure compared with the normotensive group. There were no differences between the pre-eclamptic and the gestational hypertensive group for any of the blood pressure parameters analysed. The best overall predictor for pre-eclampsia was 24-hour mean diastolic pressure which using a cutoff level of 71 mmHg gave a test with a sensitivity of only 22% and a positive predictive value of 15%. CONCLUSION: Because the absolute differences are small and the overlap between the hypertensive and normotensive groups large, ambulatory blood pressure measurement, in a healthy primigravid population, between 18 and 24 weeks of gestation is not a useful predictor of hypertension.

Adult↗
PubMed1997

Nocturnal blood pressure fall on ambulatory monitoring in a large international database. The "Ad Hoc' Working Group.

A wide range of definitions is used to distinguish subjects in whom blood pressure (BP) falls at night (dippers) from their counterparts (nondippers). In an attempt to standardize the definition of nondipping, we determined the nocturnal BP fall and night-day BP ratio by 24-hour ambulatory monitoring in 4765 normotensive and 2555 hypertensive subjects from 10 to 99 years old. In all subjects combined, the systolic/diastolic nocturnal fall and corresponding ratio averaged (+/- SD) -16.7 +/- 11.0/ -13.6 +/- 8.1 mm Hg and 87.2 +/- 8.0%/83.1 +/- 9.6%, respectively. In normotensive subjects, the 95th percentiles were -0.3/-1.1 mm Hg for the nocturnal fall and 99.7%/98.3% for the night-day ratio. Both the fall and ratio showed a curvilinear correlation with age. The smallest fall and largest ratio were observed in older (> or = 70 years) subjects. A higher BP on conventional sphygmomanometry was associated with a larger systolic (partial r = .11) and diastolic (r = .12) nocturnal BP fall. The diastolic (r = .08) but not the systolic night-day ratio increased with higher conventional BP. The nocturnal BP fall was larger and the corresponding night-day ratio smaller in oscillometric (n = 5884) than in auscultatory (n = 1436) recordings, in males (n = 3730) than in females (n = 3590), and in Europe (n = 4556) than in the other continents (n = 2764). The distributions of the nocturnal BP fall and night-day ratio showed considerable overlap among normotensive and hypertensive subjects, but the overlap tended to be larger for the ratio than for the fall. Of all subjects, 3.2% had systolic and diastolic ratios of 100% or more. With adjustments applied for confounders, the probability of being a nondipper increased 2.8 times (95% confidence interval, 2.0-4.0) from 30 to 60 years and 5.7 times (4.4-7.4) from 60 to 80 years. The odds ratios were 1.0 (0.8-1.4) for males versus females. 1.6 (1.2-2.1) for subjects with definite hypertension versus normotensive subjects, 2.4 (1.2-4.7) for Asians (n = 2213, 96% Japanese) versus inhabitants of the other continents, and 2.4 (1.5-3.8) for subjects examined with auscultatory versus oscillometric devices. In conclusion, the mathematical definition of nondipping, ie, having a night-day ratio of 100% or more for systolic and diastolic BPs, closely approximated the 95th percentiles of the night-day ratio in normotensive subjects. The ratio depends less on BP level than the nocturnal BP fall and is therefore to be preferred in the definition of dipping status. Notwithstanding the present findings, the reproducibility of nondipping and its prognostic significance need further clarification.

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

Towards the automation of validation of blood pressure monitors.

When the technique of blood pressure measurement was introduced into clinical medicine in the early years of this century, the importance of accuracy and the limitations of the technique were well recognized [1]. However, the standards called for by the clinicians and scientists who pioneered blood pressure measurement were relaxed as the 20th century progressed. Now, once again, the methodology of blood pressure measurement both in clinical practice and in research in hypertension is recognized to be a cause for concern [2].

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

In vitro hypoxia on rat pulmonary artery: effects on contractions to spasmogens and role of KATP channels.

The effect of in vitro hypoxia for 1 h on concentration-response curves to vasoconstrictor spasmogens was examined in rat isolated pulmonary arteries. Hypoxia, like levcromakalim (KATP channel opener), did not affect contractions to endothelin-1 but attenuated contractions to U46619 ((1,5,5,)-hydroxy-11 alpha, 9 alpha-epoxymethano) prosta 5Z, 13E-dienoic acid; thromboxane-mimetic), angiotensin II, noradrenaline and 5-hydroxytryptamine. The attenuation was prevented by glybenclamide. In pre-contracted arteries, subsequent exposure to hypoxia caused a response consisting of four phases (transient relaxation due to endothelium-derived nitric oxide; transient contraction; slow relaxation; sustained contraction). Glybenclamide, if added before hypoxia, did not eliminate either of the relaxant phases but, if added during the sustained contractile phase, caused further contraction. We conclude that exposure of pulmonary arteries to prolonged hypoxia causes KATP channels to open, as in systemic arteries; this diminishes contractions to some, but not all, vasoconstrictor spasmogens. The data suggest that endothelin-1, unlike other vasoconstrictors, would remain a highly effective pulmonary vasoconstrictor under severe hypoxic conditions.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗
PubMed1996

Cholesterol levels in children: to screen or not to screen.

Universal screening and targeted screening are the two approaches used in pediatric practice to identify children with elevated cholesterol levels. This study reports total cholesterol levels in 415 2-year-old children and the relationship of these results to risk factors. Based on these data, universal screening for total cholesterol (TC) does not appear to be necessary. Targeted screening for TC may be the more practical method for identifying children with dangerously high TC elevations.

Child, Preschool↗