Assessment and diagnosis in one quick step.
Explore the source record for details and available documents.
Humans↗
Biomedical subjects
J Conway
Publications and source records attributed to J Conway.
Ambulatory pressure monitoring in the assessment of antihypertensive therapy.
A low-cost, ambulatory blood-pressure monitor has been calibrated and validated against a random zero sphygmomanometer. The repeatability of ambulatory pressure recordings after a placebo month in 44 mild to moderate untreated hypertensives was assessed. Systolic blood pressure showed a mean difference over 1 month of 2.0 mmHg, with a standard deviation of differences of 9.3 mmHg. The diastolic blood pressure mean difference was 0.1 mmHg (SD = 6.3 mmHg). This variability was much less than for clinic readings (SD = 17.3 mmHg) or for single home pressure readings (SD = 19.7 mmHg). Using ambulatory monitoring to detect a drop in pressure of 8/5 mmHg with a power of 0.9, the number of subjects needed in a parallel group trial is reduced from 360 to 68, and in a crossover study from 88 to 16 subjects. The usefulness of ambulatory pressure monitoring is demonstrated in a placebo-controlled comparison of atenolol, nifedipine retard, or their combination in random order. Eleven subjects, 21-60 years, with initial average blood pressures of 166.5/104.7 mmHg, showed a reduction in pressure with atenolol 50 mg a day of 15.1/10.0 mmHg, with nifedipine retard 20 mg b.i.d. of 21.0/11.6 mmHg, and with atenolol 50 mg and nifedipine retard 20 mg once a day of 26.2/16.8 mmHg. Ambulatory monitoring of pressure improved the accuracy of the trial and demonstrated a reduction in the alerting response with atenolol.
Adult↗
Changes in arterial plasma potassium and ventilation during exercise in man.
We have investigated the relationship between arterial plasma potassium ( [K+]a) and ventilation (VE) in man because hyperkalaemia has been shown to increase VE in the anaesthetized cat by direct stimulation of the arterial chemoreceptors. Six healthy male volunteers undertook about of sub-maximal (100 W) and maximal (sprint ca. 350 W) exercise on a cycle ergometer. VE was measured breath-by-breath and arterial blood was sampled at regular intervals from a catheter inserted into a brachial artery for measurement of [K+]a and base excess. Changes in [K+]a closely mirrored changes in VE during exercise and recovery. At 100 W [K+]a increased from 4 mM to 5 mM, and during the sprint [K+]a increased to ca. 7 mM. Base excess did not mirror VE in that it reached its nadir 1-3 min after exercise had stopped, when [K+]a and VE were both falling. The increases in [K+]a seen here are probably sufficient to enhance the arterial chemoreceptor drive during exercise. Furthermore, the close temporal relationship between [K+]a and VE suggests that it is possible that exercise hyperkalaemia may contribute to the control of breathing in exercise.
Arteries↗
Correlation of blood pressure in normotensive and hypertensive individuals with platelet but not lymphocyte intracellular free calcium concentrations.
1. Fifty-two normotensive and essential hypertensive subjects were studied. Intracellular free calcium concentration [( Ca2+]i) was measured in lymphocytes (37 subjects) and platelets (18 subjects) by means of the fluorescent indicators, quin 2 and fura-2. In 31 subjects, plasma ionized calcium concentration was also measured. 2. There was a positive correlation between platelet [Ca2+]i and systolic blood pressure (r = 0.485, P less than 0.05), diastolic blood pressure (r = 0.542, P less than 0.02) and mean blood pressure (r = 0.534, P less than 0.02). 3. No statistically significant relationship was observed between plasma ionized calcium and blood pressure. 4. No relationship was found between lymphocyte [Ca2+]i and blood pressure, or between lymphocyte [Ca2+]i and plasma ionized calcium. 5. There was no relationship between [Ca2+]i of lymphocytes and platelets measured simultaneously from the same subject. 6. These findings reconcile previous conflicting reports and show a relationship between platelet but not lymphocyte [Ca2+]i and blood pressure in man.
Adult↗
First Björn Folkow Award lecture. The role of cardiac output in the control of blood pressure.
Vascular hypertrophy occurs in both primary and secondary hypertension. The degree of hypertrophy is related to the level of blood pressure and its presence can be detected in borderline hypertensives. Hypertrophy causes an increase in resistance to blood flow which is most apparent during exercise. Its presence exaggerates the responses to vasoconstrictor and dilator stimuli and this makes it impossible to estimate vasomotor tone in man. The baroreflex controls variations in blood pressure and, to some extent, the blood pressure level by modifying cardiac output.
Animals↗
Occupational low-back injury in a hospital employee population: an epidemiologic analysis of multiple risk factors of a high-risk occupational group.
A case-control study was carried out using 84 cases of employee back injuries and 168 controls (matched triplets) at Children's Hospital and Health Center, San Diego. The objective was to examine the impact of multiple individual and work-related risk factors for low-back injury from hospital employee health records. Hospital workers include occupational groups historically regarded as being at high risk, particularly nurses and others involved in patient care. In terms of traditional risk factors, significant associations were found for history of low-back pain or "slipped disc" by self-report and for history of previous back injury. Working the day shift also was significant (odds ratio [OR] = 2.23, P less than 0.005). Marital status (single) approached significance (OR = 1.65, confidence interval [CI] = 0.091, 2.99), as did low body weight (OR = 1.47, Cl 0.70, 3.10). No significant association was found between cigarette smoking and low-back injury. Possible work site health promotion interventions to lower the risk of low-back injury in this population are suggested.
Adult↗
Systemic and forearm vascular resistance changes after upright bicycle exercise in man.
1. Blood pressure, cardiac function and forearm blood flow following voluntary maximal upright bicycle exercise were studied in thirteen normal volunteers in a cross-over design against a control day. 2. After exercise there was a short-lived (5-10 min) increase in systolic blood pressure, peak aortic blood velocity and aortic acceleration suggesting a persistence of the positive inotropic influence of exercise. 3. Systemic vasodilation, which was seen immediately exercise stopped, lasted at least 60 min. This was associated with a reduction in diastolic blood pressure for the whole hour. After 30 min systolic blood pressure was also reduced. Heart rate and cardiac output were still significantly elevated and systemic vascular resistance still reduced at 60 min post-exercise. 4. A non-exercising limb vascular bed (forearm) showed a marked vasodilation for 1 h after predominately leg exercise indicating the presence of a vasodilatory influence affecting vascular beds other than the exercising muscle groups.
Adolescent↗
Treatment of tumours of the parotid gland and middle ear using obliquely reconstructed computed tomographic images.
Conventional planning of radiotherapy of tumours of the parotid, middle ear and other tumours in the head and neck often requires the treatment plane to be non-transverse. This produces major problems in delineating the tumour as well as verifying that vital structures such as the spinal cord are not included in the target volume. The use of computed tomography (CT) generally overcomes some of these problems and we have developed an algorithm to reconstruct transverse CT images into the appropriate oblique plane. Software has been written on the Picker Independent Treatment Planning System (ITPS) to allow planning on central axis and off-axis oblique planes. In addition we have used a beam's eye view facility to aid in the verification process.
Ear Neoplasms↗
Value of ambulatory blood pressure monitoring in clinical pharmacology.
Ambulatory monitoring of blood pressure can improve clinical trials in two ways, first, by the identification and exclusion of those patients in whom the blood pressure is raised only in the clinic environment and second, by improving the repeatability of blood pressure estimations. In 75 subjects the standard deviation of the difference in diastolic pressure between two clinic readings taken a month apart was 12.3 mmHg. On ambulatory monitoring this fell to 6.3 mmHg. Since the number of subjects needed in a trial is related to the square of the standard deviation of the difference, the improved repeatability leads to a substantial reduction in the number of subjects needed. However, to achieve an adequate repeatability, at least 20 blood pressure readings are required per day.
Antihypertensive Agents↗
Predicting the blood pressure response to atenolol.
The fall in blood pressure in response to atenolol 50 mg per day has been estimated using ambulatory BP and heart rate monitoring during the day in 35 mild to moderate hypertensive patients. The fall in pressure for the group averaged 18.2 +/- 11.3/11.5 +/- 8.3 mmHg. The 95% confidence internals were 14.5-22.0 mmHg systolic and 8.8-14.3 mmHg diastolic with the individual responses in diastolic pressure being related to the pretreatment variability of diastolic pressure (r = 0.65 P less than 0.001) and to the initial heart rate (r = 0.35 P less than 0.05). With atenolol treatment the BP fall is greater in patients with a more unstable BP. Blood pressure reduction is achieved by reducing the level of cardiac activity.
Adult↗
Doppler ultrasound signal analysis based on the TMS320 signal processor.
Doppler ultrasound is an established method for the study of haemodynamics. Considerable improvement in accuracy and resolution can be achieved by utilizing advanced data processing techniques. Such a system has been developed and used to assess the cardiac component of the Baroreceptor Reflex in adults and to examine cerebral blood flow in neonates.
Blood Flow Velocity↗
Quantitative assessment of impedance tomography for temperature measurements in microwave hyperthermia.
The objective of this study is a non-invasive assessment of the thermal dose in microwave hyperthermia. We intend to monitor the induced temperature rise via the change in the resistivity of body tissue, and hence control the microwave power during treatment. An initial feasibility study using electrical impedance tomography in vivo has indicated that a microwave induced temperature difference of a suitable magnitude can be mapped from a knowledge of the temperature coefficient of conductivity for tissue (typically 2% per degrees C). The accuracy of the currently employed reconstruction algorithm is assessed from data simulated by finite element prediction methods. A circular arrangement of electrodes surrounding a conductive sheet is used to evaluate the voltage distribution on the boundary of the sheet. A range of regions inside the circular field are chosen and the conductivity is changed uniformly by steps of 1% up to 10%. Images of these changes are produced. It is noticed that the algorithm underestimates the values of resistivity change for the small areas and overestimates the change for the larger areas. We are studying results for a variety of shapes of surface regions of the body that undergo resistivity change with microwave heating applied. Further work is necessary to account for three-dimensional current paths. Preliminary results are also presented of experimental investigations of the microwave-induced temperature rise in layers of carbon-loaded paper sheet.
Body Temperature↗
Changes in autonomic regulation induced by physical training in mild hypertension.
The adaptive effects of physical training on cardiovascular control mechanisms were studied in 11 subjects with mild hypertension. In these subjects we assessed the gain of the heart period-systolic arterial pressure relationship in the unfit and the fit state by using 1) an open loop approach, whereby the gain is expressed by the slope of the regression of heart period as a function of systolic arterial pressure, during a phenylephrine-induced pressure rise and 2) a closed loop approach with proper simplification, whereby the gain is expressed by the index alpha, obtained through simultaneous spectral analysis of the spontaneous variabilities of heart period and systolic arterial pressure. Both methods indicated that training significantly increased the gain of the relationship between heart period and systolic arterial pressure at rest and reduced arterial pressure and increased heart period significantly. This gain was drastically reduced during bicycle exercise both in the unfit and fit state. In a second group of normotensive (n = 7; systolic pressure, 133 +/- 3 mm Hg) and hypertensive (n = 7; systolic pressure, 180 +/- 10 mm Hg) subjects undergoing 24-hour diagnostic continuous electrocardiographic and high fidelity arterial pressure monitoring, the index alpha was significantly reduced in the hypertensive group at rest. Furthermore, when analyzed continuously over the entire 24-hour period, this index underwent minute-to-minute changes with lower values during the day and higher values during the night. We propose the index alpha as a quantitative indicator of the changes in the gain of baroreceptor mechanisms occurring with physical training in mild hypertension and during a 24-hour period in ambulatory subjects.
Adult↗
Occupational health risks for Mexican women: the case of the maquiladora along the Mexican-United States border.
International reports of morbidity among female workers in Mexico's border zone have raised concern about the occupational health of female workers in maquiladora plants (foreign-owned border industries with special tariff benefits). Commentators have suggested that U.S. industries may be exploiting workers by transferring work to nations with less stringent health and safety regulation through the maquiladora program. Using data from a larger evaluation of the effectiveness of Project Concern and a specially developed questionnaire, this study investigated the extent to which female workers reported higher morbidity rates than women with other employment and women not employed outside the home in seven colonias (communities) in Tijuana, Baja California, Mexico. Results showed essentially no difference in many short-term self-reported symptoms of illness among maquiladora workers and two other groups. Women who worked exclusively in the home reported the greatest number of symptoms. These results suggest that additional primary care services may be needed for women who have primarily domestic responsibilities. Additional research is needed to assess the risks for long-latency morbidity.
Accidents, Occupational↗
Is the antihypertensive effect of captopril influenced by the dosage frequency? A study with ambulatory monitoring.
When captopril was first introduced for the management of hypertension, its short plasma half-life led to its use as a thrice daily regimen. However, further experience suggests that the biological action is more prolonged than the plasma half-life might suggest. This study examined the effect of varying the frequency of administration (once, twice and three times daily) of a fixed daily dosage of 75 mg captopril on ambulatory BP in a double-blind cross-over study in 15 patients with mild to moderate hypertension. Each patient had six ambulatory BP recordings with placebo alternating with active phase. The three regimens (75 mg daily, 37.5 mg twice daily and 25 mg three times daily) reduced the daily mean BP equally and significantly compared with placebo. Three patients with very high pretreatment plasma renin values showed some loss of BP control immediately prior to the first dose in the morning in the 75 mg single dose phase (i.e. 24 hours post dose); but group analysis showed no difference in mean BP at this time point with the three treatment regimens. We conclude that in spite of its short plasma half-life, captopril can effectively control BP over the whole day with a once daily regimen.
Adult↗
The use of ambulatory blood pressure monitoring to improve the accuracy and reduce the numbers of subjects in clinical trials of antihypertensive agents.
A low-cost ambulatory blood pressure measuring device has been developed from a commercially available stationary apparatus. The device, which has been compared for accuracy with a mercury manometer, has functioned satisfactorily as an ambulatory monitor for 4 years. To minimize errors, blood pressure readings were made in the sitting position at half-hourly intervals over the waking day. The utility of the device in clinical trials has been investigated. On repeated readings no placebo effect on blood pressure was detectable and the mean difference between two readings in 42 subjects was 1.9/-0.33 mmHg. The standard deviation of the difference were 8.1/5.6 mmHg. This should make it possible to detect differences of 8/5 mmHg between two treatments in about 16 subjects. There was no detectable tendency for blood pressure to change during the day but the variability between readings was substantially increased if the observation periods were reduced to 4 h.
Adult↗
Complement-mediated autoimmune thrombocytopenia. Monoclonal IgM antiplatelet antibody associated with lymphoreticular malignant disease.
Explore the source record for details and available documents.
Antibodies, Monoclonal↗
Electrical impedance tomography for thermal monitoring of hyperthermia treatment: an assessment using in vitro and in vivo measurements.
For the hyperthermia treatment of human cancers considerable advantage would be gained from the ability to map temperatures deep within the body by non-invasive methods. This could be achieved by the measurement of some parameter that is sensitive to temperature change but insensitive to all other influences. Such a system must also be capable of operating in strong EM fields and be easily accommodated within all hyperthermia treatment configurations. A new thermal imaging technique by mapping electrical conductivity changes with temperature has been investigated. Temperature changes could, in principle, be deduced from this measured data if the temperature coefficient of conductivity for tissue (typically 2% per degree C) is known. Experimental studies have been performed with a 16-electrode system using an agar phantom (conductivity 2.0 S m-1). Heating of a small area of the surface is achieved using a 2 cm diameter microwave diathermy applicator. A time series of images readily shows the distribution of thermal changes and suggests a temperature resolution better than 1 degree C. In vivo experiments were performed by heating the scapula region of a volunteer while monitoring the induced temperature change with the same electrode configuration affixed to the skin surface. These results show a greater degree of image artefacts compared with the phantom results, possibly caused by a combination of body movement, blood flow effects and electrode contact degradation. These initial experiments have demonstrated the feasibility of non-invasive thermal mapping using electrical impedance imaging. Phantom studies have shown the possibility of displaying the thermal distribution induced by microwave applicators for both profile and depth planes in tissue.(ABSTRACT TRUNCATED AT 250 WORDS)
Agar↗